Taxonomy Term en 21312 Learn Sustainable Design without Having to Brave the Cold and Snow

A new round of online BAC Sustainable Design courses is starting up soon. Going out in the polar vortex is not a prerequisite.

I’m about to start teaching another round of my online course, Resilient Design, at Boston Architectural College (BAC), and this provides an opportunity to reflect on teaching at BAC and, more broadly, the online instruction in sustainable design offered through this program.

20 excellent online courses

I first started teaching at BAC in 2005, when the college’s online instruction program in sustainable design was just getting under way. At that time, BuildingGreen partnered with BAC to help design the curriculum, find the best instructors available, and promote the courses being offered.

Early on, when we had just a handful of courses, I taught Sustainable Design as a Way of Thinking, a course now being ably taught by my friend David Foley. Today, the online offerings totaling almost 20 courses are housed in BAC’s Sustainable Design Institute.

Last year, I rolled out a new course examining how to achieve more resilient buildings and communities. I’ll describe more about that below. I also participate twice a year in the week-long onsite intensives that are an integral part of BAC’s relatively new Masters in Design Studies (MDS) in Sustainable Design draws from a diverse international community.

But first, I wanted to share a few snippets from my teaching experiences at BAC.

A global student body

I keep running into students whom I’ve taught. Some are now sustainable design leaders at leading architecture firms. Others are policy makers working to institute sustainability and resilience into standard practice. Quite a few are from far away—people I’ve never met, but have been impressed with their activities.

In particular, when I teach in the on-site intensives I’m always blown away by the fascinating backgrounds of students—local students from the Boston area to students from Mexico, South America, the Middle East…most anywhere.

I’ve had students in the U.S. Military serving abroad and wanting to build skills for a new career. I’ve had students who have been in one career for decades and want to do something new. It’s incredibly inspiring to learn their stories and hear about their projects at BAC—particularly those projects that will serve to better conditions in less developed countries.

Coursework from the real world

My Resilient Design course is one of 14 online courses that start on March 23. With a maximum of 15 students, we examine the full range of resilient design measures at both building and community scales. We dive into building design, storm resilience, land-use issues, water, community, and food. And we have a great time in the online discussion forums.

With this offering of the course, I’m going to weave in some work I’m involved with in crafting LEED Pilot Credits on Resilience—so it will provide an opportunity not only to learn about resilience but also be part of an effort to enhance the way the LEED rating systems address resilience.

It should be a lot of fun.

Below I’ve listed the other courses offered this term. All are eight-week courses:

The half-semester, graduate-level courses are online, instructor-led, interactive, and asynchronous (meaning that students can access the materials any time). Courses may be taken individually or as part of the Institute’s Sustainable Design Certificate Program.

Up to 6 Institute courses are also transferrable as electives into the BAC’s online Master of Design Studies in Sustainable Design degree. See the for details.

To learn more (and register) go to, call 617-585-0101 or send an email to the BAC's Director of Sustainable Design, Shaun O’Rourke.

2015-03-02 n/a 19396 Our Energy Solutions Have All Been Found

Not really, of course. But after five-plus years I’m ending my weekly Energy Solutions blog to focus more on the Resilient Design Institute and re-making Leonard Farm back into a farm.

Our completed house and barn in the early morning light a few months ago.
Photo Credit: Alex Wilson


Back in June, 2008 I started writing a weekly column on energy for the Brattleboro Reformer, our local newspaper. I thought it would be fun to write a regular column on a topic that I’ve focused so much time on over the past 35-plus years. I was pretty confident that I could come up with enough topics to write a year’s worth of columns, and I thought some of the Reformer’s readers would appreciate such a column—geeky as it might be.

Somewhat to my surprise, the editor said sure, and I’ve been writing the weekly Energy Solutions column ever since—except during an eight-month period in 2011 when I was on sabbatical from BuildingGreen and needing the freedom to travel and focus on launching the nonprofit Resilient Design Institute. My colleague Tristan Roberts took over for me then.

For much of that time I’ve been posting these musings as blogs on That’s been a bit of a challenge, because I’ve tried to write the column/blog to serve both a lay audience and practitioners. This has led to occasional complaints by the newspaper readers that it’s too technical and complaints by blog readers that it’s too simplistic.

But mostly I’ve been able to find that balance to have some content appropriate for everyone.

This is my 273rd column/blog. At about 900 words per, that’s nearly 250,000 words—20% more words than Herman Melville’s Moby Dick. Enough already!

Another view of the house, with the barn roof (and its solar panels) just visible in the back.
Photo Credit: Alex Wilson

Back to the land

While there is lots more that could be said about energy, I’m feeling a need to shift my focus. With summer here I’m wanting to devote my weekends to creating the farm in Dummerston, Vermont that I’ve alluded to now and then in my blogs. We are looking for the right farmer to work with in creating a farming enterprise, but meanwhile I'm putting seeds in the ground.

I also want more time for other creative endeavors. Writing the Energy Solutions blog has been a regular part of my weekend these past five-plus years—just ask my wife, Jerelyn! Usually it isn’t a huge amount of time—typically one to three hours (sometimes considerably more)—but it takes a surprising amount of effort to come up with topics that can be presented in a way that’s both understandable to a lay audience and informative to green building professionals.

I’m also wanting to devote more of my creative energy to writing about resilient design and build more of a reader base on I just haven't been finding the time, and I need to change that.

Mulching newly planted fruit trees with the tractor I found on Craigslist a couple of years ago.
Photo Credit: Alex Wilson

I’ll miss the feedback and questions

In saying goodbye to my Energy Solutions blog I’ll miss the reader comments and the input. I’ll even (sort of) miss the calls and email queries I’ve gotten pretty regularly since starting the column. Many of those start with something like, “Alex, I’ve been thinking of adding insulation to my attic…” or “our boiler is on the fritz and we’re thinking of…”

I consider myself an educator, so I like being able to help people out. I also like the fact that those people I’m reaching—either through the articles or follow-up calls—are reducing their energy consumption, contributing less to climate change, and in many other ways helping create a better environment.

But I’ll be glad to dial it back a bit.

We put in about a quarter-acre of heirloom pumpkins that a local brewer wants for his seasonal beers this fall along with some other crops.
Photo Credit: Alex Wilson

Parting thoughts on energy

If I can leave you with a few take-away thoughts on energy it is these:

  • Start with energy conservation. While not as glamorous as solar panels on the roof or a plug-in hybrid in the driveway, energy conservation is usually the smartest choice. Add insulation to your house (or that of your clients) so that the furnace or boiler doesn’t have to work as hard; build smaller so you’re heating and cooling less space; combine driving trips or ride a bicycle to reduce the need for your car; wash your clothes in cold water. A kilowatt-hour or gallon of heating oil saved is usually cheaper than one that is consumed even with the highest efficiency equipment.
  • Implement passive solutions. When it comes to house design, rely on passive solar design, passive cooling strategies (such as overhangs to shade windows), and natural daylighting strategies to reduce the daytime needs for electric lighting.
  • Install high-efficiency equipment. Once loads have been reduced and passive systems have been incorporated to the extent possible, install high-efficiency mechanical systems (furnaces, boilers, water heaters, lighting equipment, appliances), water-conserving plumbing fixtures (low-flow showerheads can dramatically reduce water heating costs), and consider fuel economy with your next car purchase.
  • Rely on renewable energy. Most renewable energy systems are still fairly expensive, so it makes sense to practice conservation first. But then, by all means, look to solar-electric (photovoltaic) modules for your electricity. Wind energy only makes economic sense on a larger scale—usually with off-shore or ridge-top installations of multiple, large turbines—but in the right location wind power is the most cost-effective renewable electricity generation option we have today. On-farm methane generation, biomass co-generation systems, and technologies like tidal power and wave power should all be considered in our efforts to move away from carbon-intensive fossil fuels.

It has been a lot of fun to write this blog, and I will continue writing articles for—though not as regularly as in the past. Those interested in following my other writing can either sign up to get email notices when I post articles on, or sign up for my Twitter feed (where I let followers know about articles I’ve published or posted). Archives of most of my columns can be found as the Energy Solutions blog on

Thanks for reading my blogs, challenging me when I’ve veered too far into the world of conjecture, and being part of the conversation. Keep in touch.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-06-11 n/a 19316 Hurricane in a Bottle: Testing Building Assemblies for Moisture Resistance

State-of-the-art testing chambers show that liquid-applied barriers outperform more typical weather barriers comprised of flashing, tape, and membranes.

BEA's building assembly test chamber in Clackamas, Oregon.
Photo Credit: Alex Wilson

When I was in Portland, Oregon for the 2014 Living Future Conference I had an opportunity to visit a facility in nearby Clackamas where building assemblies and components can be tested for water intrusion and water vapor penetration.

Prosoco, a leading manufacturer of liquid-applied membranes developed the Clackamas test facility with partner company Building Envelope Innovations (BEI).

A Cat 5 hurricane in a closed chamber

At the Clackamas test facility Building Envelope Analysis (BEA)—a joint venture between Prosoco and BEI—has two specialized test chambers that can be used to simulate weather conditions as well as more insidious humidity conditions that can drive moisture into wall assemblies or damage building components like insulation and sheathing.

With the large chamber we watched as the submarine-like glass doors were closed and the fury of wind and driving rain were cranked up on the controls. We could see on manometers just how much pressure the wall assembly was having to endure, and we could watch high-pressure nozzles spraying high-velocity streams of water at the assembly.

Tom Schneider of Building Envelope Innovations explaining operation of the large test chamber.
Photo Credit: Alex Wilson

The operator can turn a few dials and simulate 150 mph wind and driving rain—wreaking havoc on the wall assembly constituents.

Prosoco company president David Boyer and BEI director of operations Tom Schneider explained how the test chamber can easily be configured to test everything from plywood sheathing and flashing systems, to windows and weather-barrier tapes.

When we visited, a high-tech, European window that had been submitted by a local Passive House builder for testing was blocked off, because it had failed so miserably that we would have had water all over the place if it hadn’t been sealed off.

Prosoco’s interest in all this testing

We didn’t get into too much detail about building the test chambers, but it appeared that hundreds of thousands of dollars had gone into designing and fabricating them. Why would Prosoco and BEI go to all this effort and expense?

BEI developed and Prosoco manufacturers liquid-applied membranes for building assemblies, and the companies want to show off how much better they perform than the far-more-common assemblage of weather-resistive barriers and specialized building tapes.

Manometers and other gauges on the test chamber.
Photo Credit: Alex Wilson

The bottom line is that the liquid-applied weather barriers, such as Prosoco's R-Guard Cat 5 Air and Water-Resistive Barrier, do a lot better than the more common taped membrane systems. While one can question how accurately the test chamber simulates real conditions, the demonstration was compelling.

In addition to the large test chamber for testing whole wall assemblies and components, there was also a smaller chamber used for testing the permeability (or vapor diffusion) of specific materials—like plywood and weather-resistive barriers.

With this discussion, I was fascinated to learn that the standard methods we use to measure the permeability of different materials to water vapor are grossly flawed. David explained that the permeability of a material that has a listed perm rating (based on standardized ASTM test methods) of 36 may drop to a perm rating of only 2 when that material gets damp from high humidity.

The smaller test chamber used for measuring moisture diffusion through different materials.
Photo Credit: Alex Wilson

Prosoco and BEI have even more sophisticated test chambers in Florida and Kansas. In addition to testing the effects of wind and wind-driven rain, the Florida facility, which I’m hoping to visit sometime, can test resistance to sudden flood or tidal surges of three to four feet.

With growing focus on resilience and adaptation to climate change, dealing with storm surges in low-lying coastal areas will become more and more important.

For related information, see BuildingGreen's course on high-performance building assemblies, as well as our EBN feature, Verifying Performance with Building Enclosure Commissioning.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-06-04 n/a 19066 Switching to a Plug-In Hybrid—With Our Own Solar Power

We oversized our PV system so that we will be able to use solar energy to power around-town driving with a plug-in hybrid

Our 12 kW PV system going in on the roof of our restored 1812 barn.
Photo Credit: Alex Wilson

Among the energy-related features of our new house in Dummerston, Vermont, is one parked in the garage.

We are hoping to power a plug-in hybrid car using the electricity generated on our barn. We have 12 kilowatts (kW) of photovoltaic (PV) modules installed on the barn (there is another 6 kW in the group-net-metered system that belongs to a neighbor), and we’re hoping that the 12 kW will be enough to not only power our all-electric house on a net-zero-energy basis, but also power our car for around-town use.

Trading up to a plug-in hybrid

My wife and I have two cars: a nine-year-old Subaru Forester with 128,000 miles on it and a ten-year-old Honda Civic Hybrid (the first year that the Civic was offered in a hybrid version) with 180,000 miles. Aside from being embarrassed by how many miles we drive—less now that our daughters are out of college—I’m aware that end-of-life decisions might be coming up soon with at least the Honda.

Our hope is to trade it in on a Chevy Volt, a Toyota Plug-in Prius, or a plug-in hybrid made by some other manufacturer. I first began thinking about a plug-in hybrid before they were commercially available, and I’m glad we waited and invested in new batteries on the Honda when the original hybrid battery system was failing a year ago at about 170,000 miles.

My brother-in-law loves his Chevy Volt. Through conversations with a number of car experts I’ve generally gotten the sense that General Motors leapfrogged Toyota with its own plug-in technology—but I’m still doing research on this. I’m hoping that by the time we really need to replace the Honda there will be even more choices.

Solar charging station at the GridStar demonstration home in Philadelphia.
Photo Credit: Alex Wilson

I’d really love it if VW introduced an affordable plug-in diesel hybrid. Prior to our two current cars, I drove VW diesels for years and loved them—first a 1983 Diesel Rabbit (which was a little too noisy and smoky) and then a 1996 TDI Passat wagon that we loved. We drove the Rabbit well into 200,000 miles with never having done anything major to the engine, transmission, or clutch. And we sold the Passat with 140,000 miles after running it for a couple years on biodiesel.

How much solar electricity would I need for around-town driving?

Back when I first started thinking about powering a car with the sun, I asked my friend Steven Strong, of Solar Design Associates in Harvard, Massachusetts, how many extra kilowatts of capacity I would need on my PV system to provide for driving. Steven had converted his standard Prius to a plug-in version by adding additional battery capacity and the necessary controls (this was before the Chevy Volt or Prius plug-in models were available).

Back in mid-2011, Steven told me that his plug-in conversion Prius required 265-275 Watt-hours (Wh) per mile in Eastern Massachusetts where it’s reasonably flat and winter temperatures are more moderate than in Vermont. He thought 300 Wh/mile would be a more realistic estimate here. He also said that the Prius conversion isn’t an optimal electric vehicle and that the next-generation, factory-engineered EVs and plug-in hybrids should provide better performance.

I just looked online and saw some claims as low as 200 Wh/mile for a Volt, but most are in the 250 to 300 Wh/mile range. If I go with Steven’s estimate of 300 Wh/mile (0.30 kWh/mile) and estimate our commuting and around-town driving to be ten trips per week at 18 miles round-trip, or 9,360 miles/yr, then our annual electricity usage for that commuting and around-town driving would be 2,800 kWh. 

Our solar array this past winter.
Photo Credit: Alex Wilson

If I assume 1,200 kWh of output per kW of rated capacity for a PV system (typical for Vermont), that works out to 2.3 kW of additional PV to generate enough electricity for that amount of driving.

Despite the fact that our HERS score (Home Energy Rating System) showed that my house will need the full output of a 12 kW PV system plus a little bit of heat from our wood stove, I’m hoping that we’ll be using less energy than the HERS model predicts (once we have our low-e storm windows up), and we’ll have enough left over for powering our around-town driving.

The proof will be in the pudding.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-05-21 n/a 19062 Low-Tech Cooling with This High-Tech Fan

The sleek, energy-efficient Haiku fan from Big Ass Fans will help keep us comfortable in our new house this summer

The Haiku fan in our upstairs guest room.
Photo Credit: Alex Wilson

As summer heats up here, I’m looking forward to trying out the high-tech ceiling fans we installed in our two upstairs bedrooms. First, let me explain why I like ceiling fans so much.

By moving air, moisture is evaporated from our skin, cooling us through evaporative cooling. With modest air movement in a room, most people will be comfortable at an air temperature at least five or six degrees Fahrenheit warmer than would otherwise be the case.

To clear up a misconception: ceiling fans do not actually cool the air in a room—in fact, they slightly increase the air temperature, because of the waste heat from the fan motor—but they allow you to be comfortable at a warmer air temperature. In other words, they raise your threshold of comfort.

If you are normally comfortable in the summer with the air temperature around 75°F, for example, with a ceiling fan operating, you might be just as comfortable with an air temperature of 81 or 82°F.

Because ceiling fans don’t involve the energy-intensive vapor-compression cycle, as do standard air conditioners, they use far less electricity, so they can save you a lot of money. A typical ceiling fan uses 90-110 watts of electricity, with Energy Star models averaging 65 watts.

For decades, ceiling fans have changed little. Often called “paddle fans” or “Casablanca fans,” most ceiling fans use rotating fan blades operated by standard AC (alternating current) electric motor. The waste heat generated by these fan motors necessitates the large, ventilated metal shroud that you see on most ceiling fans. Many of these fans become noisy as they age, as heat results in delamination of steel in the motor core.

Detail photo showing the Haiku fan in natural bamboo.
Photo Credit: Big Ass Fans

Enter the Haiku fan

Several years ago, the uniquely named company Big Ass Fans, long a leading manufacturer of very large fans used for commercial buildings and warehouses, introduced their first residential ceiling fan, trademarked Haiku. In late 2012, BuildingGreen, impressed by Haiku’s energy performance and elegance, named this a Top-10 Green Building Product for 2013. I was anxious to try out these fans in our new house.

The Haiku fan features a sleek, attractive, aerodynamic design for the airfoils (blades) in either bamboo or a plastic composite. All Haiku fans are 60 inches in diameter. Our fans are made of the composite material, in white; they elicit great comments from most visitors to our house.

Haiku fans have brushless, DC (direct-current) motors with advanced electronic controls; these are known as electronically commutated motors, or ECMs. The Haiku has seven speeds, compared with just three for standard ceiling fans. These features contribute to the very low energy consumption of just 2 to 30 watts, depending on the speed.

Haiku fans are by far the most energy-efficient fans rated by Energy Star, exceeding the Energy Star requirements by 450% to 750%.

Quiet operation and multiple settings

One of the features I’m most excited about is the incredibly quiet operation. At lower speeds, you can’t even hear the fan. Noise had kept us (mostly my wife) away from ceiling fans in the past.

Along with the multiple speeds, the fan can be operated in reverse (pulling air up rather than pushing it down), a timer can automatically turn it off, and there’s a unique “whoosh” setting that varies the fan speed to mimic natural breezes.

All these features are controlled by a very compact remote that fits into a plastic pocket that can be mounted to a wall. There are blue LEDs on the fan showing the fan speed. These stay illuminated for a few minutes then turn off.

With the high ceiling in the center, we were able to order a fan with a longer stem.
Photo Credit: Alex Wilson

A premium price for a premium product

Be aware that Haiku fans are not cheap. The composite fans (in black or white) list for $895 from the Haiku website. The bamboo fans (in a natural bamboo or a darker cocoa color) are $100 more. This compares with just $100 to $200 for most ceiling fans on the market.

Haiku fans can be ordered with different stem lengths, depending on your ceiling height, and for flat or sloped ceilings. They are also available with integral LED lights, though I haven’t seen those and can’t comment on how they look.

All Haiku fans carry a lifetime warranty.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-05-14 n/a 19051 Making Your Family Safer Through Resilience Strategies

Whether or not you believe that climate change is happening, implementing resilient design strategies will make you and your family safer—and help reduce greenhouse gas emissions

Our completed house and restored barn — which provides a model of resilience.
Photo Credit: Alex Wilson


Using cynical tactics described in the 2008 book Doubt is Their Product, climate change deniers have convinced a large percentage of the public and the majority of legislators from a certain political party believe that the jury is still out on global climate change.

With decision-making based on science seemingly impossible and new extraction technologies enabling us to extract ever-harder-to-reach oil and gas, what should we do to slow our greenhouse gas emissions? How can we convince people to take action?

The case for resilience

As defined by the Resilient Design Institute, “Resilience is the capacity to adapt to changing conditions and to maintain or regain functionality and vitality in the face of stress or disturbance.  It is the capacity to bounce back after a disturbance or interruption of some sort.”

Designing houses and apartment buildings to achieve resilience will keep people safer in the event of a disaster of some sort—whether a hurricane that might be more intense because of a warmer ocean, an earthquake that has nothing to do with climate change, or a power outage caused by terrorists hacking into our power grid controls.

You don’t have to believe in climate change to want to create safer homes for your family. It’s not a Blue State argument or one that is owned by Democrats. Indeed, I’ve observed that Tea Party libertarians are sometimes the most receptive to the resilience argument. They want to be free from the tyranny of big government, but some of them also want to be less dependent on those systems that are controlled by government—like electricity distribution and national transportation networks.

Low-energy buildings are more resilient

Nearly nine years ago, following Hurricane Katrina, I began advancing the idea of passive survivability: ensuring that buildings will provide livable conditions in the event of extended loss of power or interruptions in heating fuel. That remains a key tenet of resilience and what I have been advancing through the Resilient Design Institute.

To create a building that will maintain livable (or habitable) temperatures if it loses power or suddenly finds itself without heating fuel requires an extremely well-insulated building envelope. The house that my wife and I recently renovated—with R-45 walls, an R-60 roof, and really good windows, along with some passive solar gain through south-facing windows—will probably not drop much below 50°F even if there’s an extended power outage in the middle of winter, and keeping a fire going in our small wood stove during a power outage will be enough to keep us fully comfortable.

In hot climates—whether or not one believes that all climates will be getting warmer—the same argument applies. Energy efficiency measures help to keep homes and apartments from getting too hot if they lose power and air conditioning can’t be used. Overheating in passively operated buildings is admittedly a bigger challenge than keeping them reasonably warm in the winter, but passive survivability in hot climates relies on such strategies as keeping direct sunlight out (especially on the east and west), reflecting sunlight off the roof, and slowing conductive heat gain through the walls and roof.

Safer buildings that mitigate climate change

The same strategies that keep us safe during power outages or interruptions in heating fuel result in dramatically lower energy consumption during normal operation. Our house in Dummerston is heated with a single 18,000 BTU/hour air-source heat pump—a small enough power draw that we can provide that electricity, on an annual basis, with a modest solar electric system (see Making Your Own Electricity: Onsite Photovoltaic Systems).

We can build or retrofit to these passive survivability or resilience standards for safety reasons and, in doing so, we’re doing a great deal to mitigate climate change—but you can disregard that last benefit if you don’t believe that climate change is happening.

Resilience makes sense whether or not climate change mitigation is a goal. I’ve often said that it will be a huge success of the Resilient Design Institute if our arguments are touted by Rush Limbaugh in his radio program—probably unlikely, but not out of the question.

Want to read more in-depth on resilient design? See Resilient Design: 7 Lessons from Early Adopters.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-05-07 n/a 18995 Taking Action on Climate Change: What Will It Take?

What will it take for policy makers and the public finally get on board with the need to do something about climate change?

The United Nations’ IPCC is leading an international effort to understand climate change, and efforts like the Kyoto Protocol have grown out of that background work. But are we getting closer to solving the problem?

The vast majority of climate scientists are telling us that we’re careening headlong into the unknown world of a rapidly warming climate, and they offer policy recommendations for addressing that. Except for a few progressive countries that have taken to heart the need to slow carbon emissions—countries like Denmark, the United Kingdom, and Sweden—there is little sign that the rest of the world is even paying attention, let alone embarking on a path that will dramatically reduce greenhouse gas emissions.

What will it take for the rest of the world to get on board?

Tuckertown, New Jersey under water on Octobr 30, 2012 during Hurricane Sandy.
Photo: U.S. Coast Guard

Peak oil?

I used to hope that the costs of extracting dwindling reserves of oil, gas, and coal would increase to the point that dramatic reductions in consumption would result. I read the articles about “peak oil” (the idea that once the peak in world oil production was reached there would be inexorable declines in production, accompanied by large increases in cost) and hoped that this could be the driver of significant reductions in fossil fuel use.

Alas, even as production of conventional oil probably did peak a few years ago, advances in extraction of unconventional oil through hydraulic fracturing (fraking), deep-seabed drilling, and other technologies compensated for the reductions in easy-to-access oil, and cost increases were largely kept in check.

Commodity pricing is tightly tied to supply and demand, though, and it’s still possible that we will see large increases in price drive conservation. But it’s also possible that costs will actually drop, making it very hard to turn our collective backs on the highly concentrated, carbon-rich fuels.

Suddenly waking up to the reality of climate change?

I have also long held out hope that science would be able to convince the public and policymakers that our current trajectory is leading us to catastrophe. This metaphor helps explain where we are:

Imagine that your doctor tells you that you have cancer. Not satisfied with that single opinion, you visit 100 doctors for their prognoses, and 98 of them tell you that even though your symptoms may not be that obvious, you have cancer and need to take immediate action to cure it. The other two doctors tell you that the little bump is nothing and you shouldn’t worry about it. Most of us would take action based on advice the 98 doctors and not the two with contradictory advice.

That’s where we are with climate change science today. Ninety-eight percent of climate scientists are telling us that our emissions of greenhouse gases are leading us inexorably to a hotter climate, melting glaciers, sea level rise, more intense storms, and a host of other effects. But a lot of us—and especially our policy makers in Washington—are listening to that 2% of climate scientists who say “don’t worry about it; go on with business as usual.”

Much of the blame for the societal doubt about climate change has to do with journalists—my own profession. In a presentation in Putney, Vermont last week, outdoor writer Tom Clynes, who wrote a fascinating article on climate change deniers for Popular Science magazine two years ago, explained that journalists are trained to present good information on the topic at hand, but then find an opposing points of view to present a “balanced perspective.”

Journalists do this in reporting on climate change, going back to the same climate-change deniers, such as the Heartland Institute, where well-funded “experts” offer the opposing view that climate change is a farce. This perpetuates the misimpression by the public that there still is a lot of doubt about the science of climate change.

So, while I will continue trying to convince the public and policy makers that climate change is real and we need to do something about it, I am increasingly doubtful that we will take significant action as long as the effects are mostly future predictions and not in our faces.

Seeing and feeling climate change

This brings me to the scenario that I think will most likely—finally—result in real action: a series of events that even the most skeptical climate-change denier cannot ignore. In the cancer analogy above, this would be the point at which the cancer metastasizes and multiple tumors appear on multiple organs in such a visible way that even those last two doctors who told you not to worry will now tell you that action is needed—though they might well say that it’s too late (sorry about that).

So, what would those climate-change events look like? How obvious would they have to be to finally convince the naysayers and create public demand for real action?

Will it be the next Hurricane Sandy, which this time hits New York and Boston with full Category-4 or Category-5 force and a commensurate storm surge? Will it be a drought in the West so severe that power plants have to shut down for lack of cooling water and the flow of food from California stops? Will it be three feet of sea level rise and an abandonment of Miami and New Orleans?

A focus on resilience

I wish that we as a society were more willing to base decisions on science, and I hope that if it takes more compelling evidence to convince policy makers to finally take real action on climate change that those wake-up calls won’t be too tragic in their outcomes.

As we wait to find out, I’m going to continue to focus on resilience as a driver of action—for more on that, see Resilient Design: 7 Lessons from Early Adopters.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-04-30 n/a 18853 How Much Water to Turn on a Light Bulb?
Cooling towers at a nuclear power plant in Byron, Illinois.
Photo Credit: Scott Olson, Getty Images

Nearly all of our methods for generating electricity involve water consumption—some a lot, some not as much. Producing electricity with hydropower is the most water-intensive method, owing to evaporation from reservoirs. Nationwide, electricity from hydropower plants consumes about 9 gallons of water per kilowatt-hour (kWh) of electricity produced.

In some parts of the world, this evaporation is a big problem because of the relative scarcity of water and its use for drinking water. In the arid Southwestern U.S. this evaporation is a huge issue, especially from reservoirs like Lake Mead.

Water use for thermoelectric power plants

Most electricity in the U.S. (about 89%) is produced using thermoelectric power plants. These use a heat source (most commonly coal, natural gas, or nuclear fission) to boil water, creating superheated, high-pressure steam. This steam spins a turbine to generate electricity. Cooling water is then used to condense the steam back to water.

Depending on the type and age of the power plant, the cooling water is once-through (pulled from a river, for example and then returned to the river at a higher temperature), provided by a cooling pond, or recirculating. The once-through systems use tremendous quantities of water, but the vast majority returns to the water source from whence it was drawn—albeit at a higher temperature (thermal pollution can be a major problem). Some evaporates, however, and is not returned to the river; this is the consumptive use.  

Recirculating cooling systems in power plants use far less water and they don’t add thermal pollution to the body of water from which the water was originally drawn, but they still evaporate considerable water—in fact, typically more than once-through cooling systems—so the consumptive water is very significant.

Comparing coal, natural gas and nuclear relative to water use

Of the three primary fuels used in thermoelectric power plants, natural gas power plants have the lowest water intensity. According to Burning Our Rivers: The Water Footprint of Electricity, by the River Network in Portland, Oregon, coal power plants consume 0.69 gallons of water per kWh of electricity produced, natural gas power plants consume 0.17 gallons/kWh, and nuclear plants 0.57 gallons/kWh.

With coal, according to the report, 73% (0.506 gal/kWh) of the water consumption is from evaporation, as described above, while 27% (0.186 gal/kWh) is from upstream sources (mostly mining, and transportation). Once-through cooling of coal plants results in consumptive water use (evaporation) of about 0.3 gal/kWh, while recirculating systems evaporate about 0.7 gal/kWh.

Water consumption from nuclear plants is similar to that of coal though the spread between once-through and recirculating systems is even greater: 0.27 gal/kWh for once-through cooling versus 0.76 for recirculating systems.

While the water intensity of natural gas power generation is a lot lower than for coal and nuclear, there are significant differences depending on the type of power plant. Combined-cycle plants are nearly two-and-a-half times as water-efficient as single-cycle power plants.

Burning Our Rivers shows very low upstream water consumption for natural gas power plants, but the report did not consider hydraulic fracturing (fraking), which results in far greater water use (typically 4-5 million gallons per well) and heavily contaminates that water. An October 2013 report on the water intensity of natural gas extraction from Marcellus Shale in Pennsylvania and West Virginia (PDF download) by researchers at Downstream Strategies and San José University sheds some light on this issue.

The massive, 377 MW Ivanpah solar-thermal power plant in California's Mojave Desert.
Photo Credit: BrightSource Energy

Solar and wind power generation

There are two primary ways electricity is generated from solar: utility-scale solar-thermal power plants and either utility-scale or building-scale photovoltaic power generation. Surprisingly, most utility-scale solar thermal is more water-intensive than coal or nuclear power plants.

From Burning Our Rivers, parabolic trough systems are shown to consume about 0.80 gal/kWh, while linear Fresnel systems consume about 1.0 gal/kWh, solar power tower systems consume 0.63 gal/kWh, and dish Stirling Engine systems, which are far less common but do not use the heat to generate steam, consume only 0.020 gal/kWh.

Adding to the challenge with large-scale solar-thermal is that these systems want to be located where there is a lot of sunlight, such as the American Southwest, and those places tend to be much drier.

Photovoltaic systems use almost no water in their operation—only 0.002 gal/kWh—with most of that upstream water use for manufacturing.

Finally, wind systems consume less than 0.001 gal/kWh—the lowest of any electricity source—with most of that also upstream.

An array of dual-axis-tracking, 25-kW SunCatcher collectors using Stirling engine technology, which does not require water.
Photo Credit: Stirling Energy Systems

Low global warming and low water use

It is worth pointing out that the renewable energy technologies for power generation that are growing the quickest in implementation (photovoltaics and wind) are the least water-intensive.

The only measures that do even better from a water-use standpoint are efficiency measures. Using less electricity is the place to start if the goal is to conserve water resources—see Saving Energy by Conserving Water, and Saving Water by Conserving Energy.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-04-16 n/a 18517 6 Ways Our Household is Saving Water—And Energy

Saving energy isn’t only about using less electricity and fuel; it’s about saving water.

Our 1.75 gpm Kohler Bancroft showerhead.
Photo Credit: Alex Wilson

In this weekly blog, I’ve focused a lot of attention on the energy-saving measures at our new home—from the innovative insulation materials we used to the air-source heat pump heating system and our top-efficiency heat-recovery ventilator. What I haven’t said much about are the measures we’ve taken to reduce water use and why these measures save energy as well.

The water-energy nexus

Before getting into specifics, it’s important to note that there is a close relationship between water and energy—even when we’re not talking about hot water. At the macro scale, it takes at lot of water to produce energy.

With electricity generation, each kilowatt-hour (kWh) of electricity generated (based on national averages) consumes 2.0 gallons of water, according to a 2003 paper by National Renewable Energy Laboratory researchers (PDF download). This is mostly from evaporation of water at thermoelectric power plants, but also includes evaporation of water at reservoirs used for hydropower generation. (See The Water-Energy Connection, and Energy Could Be Twice as Thirsty by 2035.)

Other energy sources consume a lot of water in production. We can refer to this as the “embodied water” of these energy sources. Simply pumping oil out of the ground isn’t all that water-intensive, but when we start getting into “enhanced recovery” technologies like hydraulic fracturing (fracking) the water intensity goes way up—and can be a limiting factor. It may increasingly lead to conflicts with farmers in arid regions that are rich in underground oil and natural gas.

Kohler Forté single-handle faucet, delivering the full 1.5 gpm.
Photo Credit: Alex Wilson

At the same time, treating and distributing water and treating wastewater use a lot of energy (see Waste Water, Want Water). This is especially the case with municipal water and sewer systems, but even in rural areas with their own water systems, water pumping can be one of the largest energy consumers—to operate deep-well, 220-volt, submersible pumps.

Water conservation

It is with this context that I consider water conservation to be an extremely important priority. We are fortunate in Vermont to have plenty of water, but I’m just back from California, which is dealing with one of the most severe droughts in decades. Flying over the Sierras on my way there I was shocked to see how little snow cover there was.

So what are the water conservation measures we implemented at our new house?

Low-flow showerheads

We installed EPA WaterSense-certified showerheads that deliver 1.75 gallons per minute (gpm), vs. the federal standard 2.5 gpm for showerheads. We are very pleased with these showerheads, though I’ve also used a showerhead using just 1.5 gpm and been very happy with that, and I recently used a showerhead rated at just 1.0 gpm and found that to work just fine (see GreenSpec for our green showerhead criteria and product listings).

When we save water with a showerhead or faucet we also typically save energy use directly, since we’re using less hot water. Indeed, in replacing older, high-flow showerheads with new low-flow models, the payback for that change is often measured in months or even weeks, instead of years.

Low-flow faucets

The faucets in our two bathrooms are WaterSense-certified at 1.5 gpm, vs. the maximum 2.2 gpm. Interestingly, almost the entire plumbing industry has shifted to 1.5 gpm flow rates—the level required for WaterSense certification. Because we rarely turn on the faucet full-force, our actual consumption is a lot lower. Screw-in faucet aerators are inexpensive and can quickly convert most standard faucets to water-saving versions. (Again, see our GreenSpec criteria for faucets, and recommended products.)

Kohler Highline 1.28 gpf toilet.
Photo Credit: Alex Wilson

Low-flush toilets

We have two bathrooms: upstairs and downstairs. Both have high-efficienct toilets (see Residential Toilets) that use just 1.28 gallons per flush (gpf). I admit to having been somewhat skeptical that 1.28 gpf would be enough for satisfactory performance, but in the three months we’ve been in the house we’ve had zero problems. The toilets are performing beautifully.

Water-efficient clothes washer

I remember when I bought my first new clothes washer 25 or 30 years ago, I had to work pretty hard to find a water-conserving horizontal-axis (front-loading) model. At the time there was only one U.S. manufacturer producing such a product for home use (White-Westinghouse).

Fortunately, it is a very different situation today, with nearly every manufacturer offering such products. We bought a Whirlpool Duet washer, which I think is the best of the U.S.-made models. We had one in our last home and were very pleased with it. The only difference with this purchase is that the washer (and matching dryer) are larger, since Whirlpool shifted manufacturing to the U.S. from Mexico, and the units grew in size. (See our tips on selecting washing machines.)

Because we typically wash clothes in cold water, our direct energy use for clothes washing is very low.

Water-efficient dishwasher

We bought a mid-range dishwasher and are very pleased with it so far. We operate it with the no-heat-dry feature selected on a normal or light cycle to further reduce water and energy use. Roughly 90% of the energy use by dishwashers is for heating the water, so a water-conserving dishwasher also saves a lot of energy. With the Normal cycle and assuming typical soiling of dishes, a load of dishes uses just 2.9 gallons—far less than was the case a decade ago.

It’s worth noting that using a modern, EnergyStar-rated dishwasher typically consumes a lot less water than washing dishes by hand.

TapMaster knee- and foot-activated faucet controller.
Photo Credit: Alex Wilson

Knee-control kitchen faucet

We brought down from the house we moved out of a great kitchen faucet control system made by TapMaster that lets you turn the faucet on an off by either pressing your knee into one of the under-sink cabinet doors or by pressing a toe plate with your foot. This way you can easily turn the water on and off while you’re washing a pot or rinsing dishes. There’s no reason to leave the water running, so moderate water savings can be achieved. It’s also a huge convenience!

Final thoughts

In the years and decades ahead, water may well be a bigger challenge than energy in many areas of the U.S. and world. We should all do our part by using this precious resource efficiently.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-04-08 n/a 18460 Urine Collection Beats Composting Toilets for Nutrient Recycling

Human urine collection and use provides a better way to recycle nutrients than use of composting toilets.

Abe Noe-Hays of the Rich Earth Institute standing in front of a urine storage tank. Click to enlarge.
Photo Credit: Alex Wilson

Just when you thought it was safe to enjoy this blog over a cup of coffee here’s an article on…urine?


Let me explain.

Urine is a largely sterile, nutrient-rich resource that can be used in fertilizing plants. In fact, according to the Rich Earth Institute, the urine from one adult in a year can provide the fertilizer for over 300 pounds of wheat—enough for nearly a loaf of bread per day.

The Rich Earth Institute is a Brattleboro, Vermont-based organization that’s at the leading edge of the little-known practice of urine collection and use—something that’s emerging in Sweden and a few other places. This past Friday night roughly 200 people gathered at the Strolling of the Heifers’ River Garden in downtown Brattleboro to hear Abe Noe-Hays and Kim Nace from the Rich Earth Institute, along with a New York City comedian/activist, Shawn Shafner, discuss the idea.

Mixing waste and potable water

With conventional practice, human waste (urine and fecal matter) is mixed with large quantities of potable water and flushed down toilets. From there, it typically flows to municipal wastewater treatment plants where energy- and chemical-intensive processes use bacteria to break down organic wastes, separate out biosolids, kill pathogens, and release that water into rivers or aquifers.

Nutrients in human waste. Note that the dry mass of urine is actually greater than that of feces and that nitrogen and phosphorous levels in urine significantly exceed those of feces. Click to enlarge.
Photo Credit: Swedish data from the Rich Earth Institute

For those living in rural areas not served by a municipal sewer system, that wastewater flows into septic tanks where solids settle out and the effluent then flows into the soil through leach fields—in most cases with most of the nutrients in that waste filtering down into the underground aquifers. I learned when researching onsite wastewater disposal years ago for Environmental Building News (see On-site Wastewater Treatment: Alternatives Offer Better Groundwater Protection, as well as the more recent Waste Water, Want Waterthat the aquifers under rural New England towns almost always have nitrate levels that significantly exceed federal drinking water standards.

At the same time, in the chemical industry, tremendous quantities of natural gas are used in the Haber-Bosch process (invented in 1915) to extract nitrogen from the atmosphere, which is made up of roughly 78% nitrogen gas (N2), to produce ammonia fertilizer, the mainstay of commercial agriculture.

A urine-separating composting toilet.
Photo Credit: Alex Wilson

Utilizing human urine

When most people think of creating fertilizer from animal waste, they think of manure. Composted cow manure, for example, is widely sold in garden centers. But there are actually far more nutrients in urine than in fecal matter.

In human waste, 88% of the nitrogen is contained in the urine, along with 66% of the phosphorous, according to Swedish research, while nearly all of the hazards—including bacterial pathogens—are contained in the fecal matter.

The idea that the Rich Earth Institute has been advancing for the past several years is to collect human urine, sanitize that urine to kill any bacteria that may be in it (from urinary tract infections, for example, or fecal contamination), and then apply it on fields as a fertilizer.

Abe Noe-Hays (who used to work for our company, BuildingGreen!), has been leading the charge with this idea in the U.S. The Rich Earth Institute secured funding from the U.S. Department of Agriculture, through the Sustainable Agriculture Research and Education (SARE) program to study urine collection and use as fertilizer, and the Institute is into its second year of this study.

Collecting urine

Specialized urine-separating flush toilets are available in Scandinavian countries with front chambers for capturing urine (GreenSpec lists two. Abe Noe-Hays manufacturers a urine-separating composting toilet (listed in GreenSpec), and the Institute provides toilet insets for urine collection. On a larger scale, collection of urine from men’s rooms that have waterless urinals is particularly easy.

With the help of Best Septic Service in Brattleboro, the Institute collected 3,000 gallons of urine from over 170 participants in 2013.


According to most experts, simply storing urine for a while in a sealed container is enough to kill bacteria, due to the high alkalinity and ammonia from the urine. But the Rich Earth Institute is experimenting with faster pasteurization systems that heat the urine (including with solar systems that circulate solar-heated fluid through heat exchangers in the urine tanks). They are also testing various strategies for controlling odor—likely the biggest hurdle we face with urine collection and use.

Jay Bailey spreading diluted urine on a hay field in Brattleboro.
Photo Credit: Abe Noe-Hays

Land application

In Sweden urine is being applied on food crops, but to date, with USDA support and permits from the State of Vermont, the Rich Earth Institute has stuck with less controversial applications on non-food crops—specifically hay fields.

Initial results last year with undiluted urine and dilution rates of 1:1 and 3:1, dramatic improvement in hay production was seen (see photo).

Because urine may contain pharmaceuticals being filtered from the body by our kidneys, there is an important question about whether that could pose a problem for use of urine as fertilizer. This year, the Institute will begin an EPA-funded study to test whether residual pharmaceuticals in urine are taken up by vegetables grown on experimental plots.

Better than composting toilets?

I have long been a fan of composting toilets. I like the idea of not mixing human waste with potable water, and I’ve always felt that flushing away the nutrients in human waste was a lost opportunity. But when I learned about urine separation and use (believe it or not in a luncheon presentation on the topic at a conference in Houston, Texas in 2009), I began to see the benefits of urine separation over standard composting toilets.

With standard composting toilets, most of the nitrogen in the waste ends up being volatized as either nitrogen gas or ammonia—and lost into the atmosphere. With urine collection and use, the nutrients aren’t lost; they are recycled in a sustainable nutrient cycle. That's part of why EBN has called urine separation "the next wave of ecological wastewater management."

Urine application test plots; the darker-green strips were fertilized with diluted urine.
Photo Credit: Abe Noe-Hays

This is something we’re considering for Leonard Farm, though we have not installed such a system yet. For more information or to participate in ongoing studies, contact the Rich Earth Institute.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-04-02 n/a 18417 Can This Man Reinvent Concrete?

A California company, Blue Planet, is reinventing concrete and envisions a world in which the 8 billion tons of concrete used each year sequester billions of tons of carbon dioxide.

Pouring the foundation for our Dummerston Home; someday soon, concrete may be able to sequester huge quantities of carbon.
Photo Credit: Alex Wilson

I’ve been in the San Francisco Bay Area for the past week speaking at various conferences. (When I travel I try to combine activities to assuage my guilt at burning all the fuel and emitting all that carbon dioxide to get there. Between conferences, I’m now spending time with my daughter in Petaluma and Napa.)

I spent three days last week at BuildWell, a small conference organized by my friend and colleague Bruce King, P.E. that is focused on “innovative materials for a greener planet.” The roster of presenters included such well-known thought leaders as Ed Mazria, FAIA of Architecture 2030, who is leading an effort to shift to zero-carbon buildings by 2030; John Warner, Ph.D., the father of Green Chemistry, which is transforming manufacturing by reducing toxicity; and Mathis Wackernagel, the founder of the Global Footprint Network.

A less-recognized presenter (and attendee throughout the three days) was Brent Constantz, Ph.D., the founder and CEO of Blue Planet and a professor at Stanford University. (Blue Planet has no website currently.) Little did I know how audacious Constantz’s plans are: to reinvent concrete, transforming it from one of the world’s largest emitters of carbon dioxide into one of the most important tools to sequester the carbon dioxide emitted from power plants.

Ordinary Portland cement

The Portland cement used today in concrete and a wide range of mortars, stuccos, and concrete masonry units (CMUs) consists largely of two forms of calcium silicate (calcium oxide plus silicon dioxide) with smaller concentrations of aluminum oxide, ferric oxide, and sulfate.

Portland cement derives its name from its similarity in appearance to Portland stone, found on the Isle of Portland in Dorset, England in the early 19th century.

The primary raw material going into Portland cement manufacture is calcium oxide (CaO), which is produced by “calcining” limestone (CaCO3), under very high temperature and the intermediate formation of “clinker.” This calcining process drives off carbon dioxide (CO2). Because such huge quantities of cement are used globally about 1.6 billion tons), Portland cement production is one of the largest sources of our carbon dioxide emissions.

Portland cement produces CO2 both from the calcining of limestone (a chemical process) and from the tremendous energy inputs used in that calcining process.

Note that Portland cement is only one constituent in concrete, accounting for about 12% of the mass of concrete—the rest is from sand, water, and aggregate. It is the binder that glues the sand and aggregate together into a solid stone-like material.

(Read more in our special report on What You Need to Know About Concrete and Green Building.)

Calcium carbonate cement

Constantz is focusing on a very different type of cement: a calcium carbonate cement. The calcium is derived either from seawater or—in more inland locations—from brine, and the carbonate comes from the carbon dioxide in power plant flue gases. He envisions a system in which the CO2 is extracted from flue gases to produce both a calcium carbonate cement and limestone aggregate.

Blue Planet, which has attracted some large investors, believes that concrete produced with its CarbonMix cement and limestone aggregate would be carbon-neutral or even carbon-negative, meaning that the more of it you use the more carbon is sequestered—or pulled out of the atmosphere and forever locked up.

Blue Planet is carrying out research at one of California’s largest power plants: a natural-gas-fired plant on the coast at Moss Landing (south of San Francisco). The Moss Landing power plant, now owned by Dynegy, power plant produces four million tons of CO2 per year—CO2 that is contributing to global warming.

In producing concrete from CarbonMix cement, carbon emission reductions would be achieved in multiple ways: the production of Portland cement would be reduced; CO2 would be chemically tied up in the calcium carbonate cement; and the aggregate (a far larger constituent of concrete) would be limestone.

Using limestone as aggregate could be done immediately, with no changes in highway standards and concrete engineering standards. And Constantz claims that even the non-Portland cement could be used with very few changes—though the lower alkalinity in cement binder may mean that different re-bar is needed. (With standard concrete, the high alkalinity protects the steel re-bar from corrosion.)

Ancillary benefits of carbon-negative concrete

In addition to the huge benefit of sequestering carbon dioxide emitted from power plants, CarbonMix cement and aggregate production could provide a way to demineralize water. Such a facility would provide a wonderful complement to a desalination plant, for example.

In desalination, fresh water is extracted from seawater or brine in a process that concentrates the calcium and other minerals. Desalination is becoming more and more common, and getting rid of the highly concentrated brine can be a challenge. Texas, for example, has almost 50 desalination plants, nearly all of them using brine rather than seawater.

Reducing the mineral content of brine is also a key priority in fracking. The oil and gas industry would love to find someone wanting to use that brine, helping to purify it in the process.

Final thoughts

It remains to be seen whether Brent Constantz can realize his vision of transforming cement and concrete—among the most common materials used in construction today. If he can, it will be a game changer—something that attendees of BuildWell were quick to grasp. If he succeeds, fortunes will be made in the process and the world will be far better for it. I look forward to watching the progress of Blue Planet over the coming months and years. BuildingGreen will be reporting on this technology as it evolves.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-03-26 n/a 18403 Our Green Home Cost a Lot, But Yours Doesn't Have To

Our house cost a lot more than I would have liked, but many of the ideas used in it could be implemented more affordably.

We picked up these two salvaged garage doors for $500 total—while new they would have cost $3,500 apiece. Using salvaged materials can save a lot of money.
Photo Credit: Alex Wilson

My wife and I tried out a lot of innovative systems and materials in the renovation/rebuild of our Dummerston, Vermont home—some of which added considerably to the project cost. Alas!

The induction cooktop that I wrote about last week is just one such example.

For me, the house has been a one-time opportunity to gain experience with state-of-the-art products and technologies, some of which are very new to the building industry (like cork insulation, which was expensive both to buy and to install). We spent a lot experimenting with new materials, construction details, and building systems. While we haven’t tallied up all the costs, we think that the house came in at about $250 per square foot.

All this has raised the very reasonable question about whether all this green-building stuff is only feasible for high-budget projects.

So I’ve been thinking about what lessons from our project would be applicable to more budget-conscious retrofits. Here are some thoughts. (Also see our recent EBN feature article, How to Build Green At No Added Cost.)

Keep it compact. In renovating the old farmhouse we shrank the footprint, eliminating a kitchen addition that had been added perhaps in the 1920s. Fitting the kitchen into the main house meant some tricky design work, but it helped us contain costs with the exterior envelope and finishes. This cost-saving strategy applies whether with new construction or renovating an existing house. The cost per square foot will likely go up with a smaller house, but the total cost should drop—and there will be less volume to heat and cool.

Deep-energy retrofit with mineral wool. The cork insulation we used as an insulation wrap on the walls was really amazing, and I’m glad we used it, but if we were doing the project over with a more constrained budget, I think I would have gone with rigid mineral wool. Carrying out a deep-energy retrofit by wrapping a house in rigid insulation is never inexpensive and it depends on having deep enough roof overhangs, but with rigid mineral wool (such as Roxul ComfortBoard or the highest-density Thermafiber product) it can be a much more reasonable retrofit. (For more details on how to do a retrofit with mineral wool, see our insulation report.)

High-performance storm windows. While our low-emissivity (low-e) storm windows on the south and east facades aren’t installed yet, they can provide a reasonably priced alternative to window replacement with top-performing, triple-glazed windows. The idea is to keep the existing (prime) windows when installing exterior rigid insulation on a house and add window surrounds to extend the window openings to the new outer face of the walls—and then install the storm windows near the outer face of the window surrounds. (See GreenSpec for guidance on finding good exterior storms.)

Air-source heat pump. The heating system we went with on our house is a great option today for compact, very-well-insulated homes, while larger, ducted versions of these systems will increasingly make sense for replacing conventional gas or oil heating systems. On a cost per million BTUs of delivered heat basis, air-source heat pumps are significantly less expensive than propane and heating oil, and they can be pretty competitive with natural gas—especially if natural gas prices keep climbing. An air-source heat pump means electric heat, but that opens the door to generating the electricity you need—now or down-the-road—with solar. (To play around with heating cost comparisons, see our heating fuel cost calculator.)

Water-efficient products. We went with state-of-the-art water-conserving plumbing fixtures and appliances. The 1.75 gallon-per-minute Kohler WaterSense showerheads in our two bathrooms significantly reduce hot water use, compared with standard 2.5 gpm models, saving energy as well as water. And they don’t cost any more than standard models.

Rain-screen detail on exterior walls. We spent a little more installing strapping over the exterior sheathing so that the siding will have an air space behind it, but the cost is low enough and the durability benefits great enough that this should be standard practice today. We will save thousands of dollars over the years by having to paint the siding only every 15-20 years (I predict), instead of as often as every five years, and a big part of the difference is the rainscreen detail.

Salvaged materials. We were able to save some money—and with more concerted effort  could have saved a lot more—by making use of salvaged materials. We bought a salvaged newel post and balustrades for the stairs, for example, picked up a discontinued floor-demo front door, purchased salvaged timbers for post replacements in the barn, and bought superb two garage doors from the now (sadly) closed ReNew Salvage in Brattleboro. Using salvaged materials not only saves money, but it can also help the environment by allowing us to save in raw materials extraction and by reducing pressure on landfills.

These are just a few examples of how a green, energy-efficiency agenda can be achieved with an eye towards economy. Building or renovating with a goal of energy savings and environmental stewardship does not have to have a huge cost impact.

Fundamentally, it’s all about savings—saving energy resources and saving the environment. If we were to put an economic value on protecting the environment, those environmental savings with our house might have compensated for the increased cost of building. But we’re not there yet.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-03-19 n/a 18382 Safe, All-Electric "Induction" Cooking: Try This At Home

Induction cooktops respond quickly, avoid gas combustion, are tops in energy efficiency, and limit risk of burns.

Our induction cooktop blends in well with our matt-black Richlite countertop. Click to enlarge.
Photo Credit: Alex Wilson

One of our early decisions in the planning for our farmhouse renovation/re-build was to avoid any fossil fuels. If the State of Vermont can have a goal to shift 90% of our energy consumption to renewable sources by 2050, we want be able to demonstrate 100% renewables for our house today.

That decision meant using electricity, rather than propane, for cooking. Electric cooking was actually a very easy decision for us. When our daughters were very young, roughly 25 years ago, my wife and I replaced our gas range with a smooth-top electric range. I had read too many articles about health risks of open combustion in houses; I didn’t want to expose our children to those combustion products.

And I knew that even the best outside-venting range hoods don’t remove all of the combustion products generated when cooking with gas.

Deciding on induction

We were surprised back in the late ’80s how quickly we adjusted to an electric cooktop. It’s not as controllable as gas, but we made due just fine for 25 years. Nonetheless, friends always complained about electric cooktops being too slow or not controllable enough, so we wanted to try out the electric option that top chefs are increasingly turning to: induction.

Controls are very easy, though all electronic. I'm hoping they'll hold up.
Photo Credit: Alex Wilson

For our new house we bought a KitchenAid induction cooktop for our kitchen island. I had wanted to go with the technology leader, Miele, but at about $2,500 for Miele’s 30-inch model, the cost was just too high for our budget. Even the less-expensive KitchenAid version stretched our budget considerably.

What is induction?

Electromagnetic induction, which was discovered in the early 1800s by Michael Faraday, is the process in which a circuit with alternating current (AC) flowing through it induces current in a material placed nearby. It is key to the functioning of induction (asynchronous) motors and most electric generators.

In the case of induction cooking, there’s an electric coil under the glass surface of the cooktop through which AC electricity flows. This current, in turn, generates current in a ferrous metal (iron or steel) pan that’s very close to it (separated by the glass cooktop). Electromagnetic current flows through the bottom of the pan, but because iron and steel aren’t very good electrical conductors, that electric current is converted into heat—more specifically, into electric resistance heat, since the material resists the flow of electric current.

Because the stovetop surface doesn't heat up, induction cooktops are much safer than any other type. This pan of water boiled with no impact to the newspaper.
Photo Credit: Alex Wilson

The result is that the pan or skillet heats up and transfers that heat to whatever is being cooked. So, in effect, the pan becomes the heat source.

If you have a rice cooker, you’re probably already using induction cooking, since that’s how most rice cookers work.

This is different than conventional electric cooktops in which the cooktop itself is heated by electric resistance, and the heat is transferred to the cooking pot. Again, with induction heating, the cooktop only has electricity running through it as it induces heating in the pot.

Advantages of induction cooking

Speed and controllability. Because the pan generates the heat directly, induction cooking is very fast—heating up immediately when turned on and cooling down immediately when the current is reduced or turned off. Heat output can be adjusted even more quickly than with gas burners.

Energy efficiency. Induction cooktops are the most efficient of any option in transferring heat generated by the stove to a pot or pan. According to a study done by Lawrence Berkeley National Laboratory for the U.S. Department of Energy, gas cooktops are about 40% efficient, electric-coil and standard smooth-top electric cooktops are 74% efficient, and induction cooktops are 84% efficient (see Table 1.7, page 1–22). Before you get all excited, though, be aware that cooking accounts for less than 3% of average household energy consumption—so don’t expect an attractive payback for the extra cost of an induction cooktop!

Only ferrous metal pans work on induction cooktops—such as cast iron and stainless steel that a magnet sticks to the bottom of.
Photo Credit: Alex Wilson

Less waste heat. Another aspect of that energy efficiency is greater summertime comfort. We’ve only been in our house for a couple months so haven’t used it in hot weather (that’s for sure!), but a friend who has an induction cooktop raves about the summertime benefit of not heating up his kitchen as much as he used to with a gas cooktop.

Safety. Induction cooktops, like other electric cooking elements, avoid combustion and gas lines, so are inherently safer than gas burners. But induction cooktops go further, dropping a piece of paper on a cooktop that’s on can’t cause a fire. In fact, as shown in the photo, you can cook with a piece of paper between the cooktop and the pot (although doing so probably isn’t a good idea). The electromagnetic induction happens through the paper.

Drawbacks of induction cooktops

Ferrous metal cooking vessels required. Aluminum, copper, and some stainless steel cookware won’t work, so buyers of induction cooktops may have to invest in new pots and pans. Use a magnet; if it sticks to the bottom of the pot, it will work on an induction cooktop. Fortunately, there are lots of options, including plenty that are reasonably affordable.

High cost. While the cost of induction cooktops has dropped in the last few years, they are still pricey. We spent $1,400 on our 30-inch KitchenAid Architect Series II induction cooktop, and the list price of that model is $1,849. A comparable KitchenAid standard electric cooktop (non-induction) lists for $1,299. The high cost of induction today is partly because of the induction technology, and partly because induction is only available in the high-end product lines from appliance manufacturers. The cost should come down and induction gains popularity and spreads into lower-priced product lines.

Health concerns? There is some concern that the electromagnetic fields (EMFs) created by induction cooktops could be hazardous. I understand that the field drops off (attenuates) very quickly with distance from the cooktop, though I haven’t borrowed a gauss meter to actually measure EMFs from our cooktop. I haven’t read credible reports of health problems from induction cooking, but I couldn't rule it out.

Our cabinets were made by Greg Goodman of Brattleboro using native sugar maple along with Columbia Forest Products' formaldehyde-free PureBond hardwood plywood.
Photo Credit: Alex Wilson

Bottom line

I like our induction cooktop a lot. I’ve only had one frustrating experience: the time last month when I set out to make a big batch of chili for an office gathering and discovered that the largest of the skillets in our cookware set doesn’t work with induction elements, even though all the others do. I’m assuming that because the diameter of that pan is so large, the manufacturer used a disk of aluminum or copper, rather than steel, to conduct the heat to the edges more evenly.

Overall, my wife and I are very pleased with induction, though it does take some getting used to. We got a rimless model, and the black ceramic-glass surface blends in quite well with the black Richlite countertop material.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-03-12 n/a 18366 Heat Pump Water Heaters in Cold Climates: Pros and Cons

While a heat-pump water heater will save significant energy on a year-round basis, be aware that in a cold climate the net performance (water heating plus space heating) will drop in the winter.

Electricity consumption by our GeoSpring heat pump water heater in February. Note the spike mid-month when I switched the mode to "boost." Click to enlarge.
Photo Credit: here

We chose a heat pump water heater for our new house, and as I've recently discussed here, there are a lot of reasons why you might be doing the same.

Using an air-source heat pump, heat pump water heaters (HPWHs) extract heat out of the air where they are located to heat the water.

That means that a HPWH cools the space where it is located. That’s a good thing in the summer—it doubles as air conditioning—but in the winter it’s not so helpful. That’s especially the case in a cold climate in a house without a standard heating system.

Cooling the space where they are located

In a typical New England house that has a furnace or boiler in the basement producing a lot of waste heat, a heat pump water heater can use some of that waste heat and it’s not really very noticeable—the less efficient the heating system the less noticeable is the effect of the HPWH.

But we don’t have a heating system in our basement. As a result, our HPWH cools the space. With the cold weather we’ve had (as I write this it’s about –2°F) and our basement has stayed pretty cool: typically 50°F–54°F, though with the exceptionally cold weather we had a few weeks ago during a time of heavier hot water usage, the temperature dropped as low as 47°F. Our basement temperature would probably be considerably lower if my wife and I used a lot of hot water, but we're pretty frugal.

Minute-by-minute electricity consumption by the water heater over a two-day period. The line in green shows consumption through mid-morning on March 5th; consumption on March 4th is shown by the gray line..
Photo Credit: here

Robbing from Peter to pay Paul

In cooling the space where it is located, a HPWH makes the heating system work harder. In our house the heating system is a single mini-split air-source heat pump wall-mounted unit on a first-floor wall. That system delivers heat to the basement through the uninsulated floor and through the basement door, which we usually leave closed.

We also have a fan and ductwork at the top of our stairs so that, if we need to, we can pull warm air from the heated space in the house and dump that into the mechanical room in our basement. This is a back-up in case the basement gets too cold, but we haven’t used that fan because of its noise.

So our 18,000 Btu/hour Mitsubishi air-source heat pump has to work harder (and use more electricity) because it’s also indirectly heating our water. With the really cold weather we’ve had since moving into the house in early January, our air-source heat pump has been working pretty hard to keep up. And I think the HPWH has contributed to our first floor being a little cool—especially near the floor.

My friend Lester Humphreys in Brattleboro, who also has a HPWH in his basement but has an oil-fired boiler there as well, has done some back-of-the-envelope calculations to estimate how much oil he’s using for his water heating and asked me to look over his numbers:

“I calculated the loss from our living space through the floor to the basement using the formula Area x 1/R x delta T.  I figure our heat pump heater lowers the temperature in the basement by about 3 degrees, our wood floor has an R value of 2.75 and the basement ceiling is 1217 square feet.  This gives me heat loss of 1314 BTUs per hour.  Running 6 hours a day (probably a little high), a delivered heat efficiency of 70% for our oil system, this equals 2.4 gallons a month (about $9), which is not bad.”

With our hot water usage, the electricity consumption directly by the HPWH isn’t that great: 56 kilowatt-hours (kWh) in February—or about $8 worth at 15¢ per kWh, which is Green Mountain Power’s current residential electric rate. Consumption averaged a little less than 2 kWh per day in February, jumping to over 8 kWh one day when both of our daughters were visiting from out-of-town and we had to switch the water heater to the “Boost” mode (in which an electric resistance heating element supplements the heat-pump mechanism).

Along with that 56 kWh used by the HPWH, though, some of the 814 kWh used in February by our mini-split air-source heat pump heating system (about $125 worth), was for water heating. I haven’t calculated what our total water heating cost was for February, but that should be possible to do.

Slow recovery

Another thing to keep in mind is that HPWHs have a quite slow recovery rate—I think ours recovers at a rate of about eight gallons per hour. This is why larger water heaters often make sense with HPWHs, though I thought a 50-gallon model would be alright for our usage.

In mid-February, though, our younger daughter from New York City and our older daughter and financé from California were visiting, and we had a party. We still might have been all right with hot water, since we have WaterSense plumbing fixtures and a high-efficiency dishwasher, but our younger decided to take a bath after we had all done a lot of party prep. She ran out of hot water before the tub was all the way filled.

Fortunately, most HPWHs, including our GE GeoSpring model, allow you to change the mode. I normally operate the water heater on Heat Pump Only mode, but switched it to Boost mode for a few hours that Saturday.

The jump in power draw was dramatic (shown by my eMonitor). In Heat Pump Only mode, the power draw peaks at about 500 watts, but that jumped to 5,000 watts in Boost mode.


The other issue to consider with HPWHs is that they have fans and compressors that are noisy. I don’t think I would consider a HPWH if we didn’t have a basement and had to place the water heater on the first floor. We have fairly good acoustic isolation between our basement and first floor—and the water heater is in a mechanical room to which we can retrofit ceiling and wall insulation if the noise proves annoying.

So far, the noise isn’t very noticeable, but in the summer (when the air-source heat pump is unlikely to be running) we may find that we can hear the water heater—in which case I’ll probably insulate the mechanical room. Noise did play into our product selection; when I was researching options, the GE GeoSpring was the quietest HPWH I found.

Bottom line

In summary, we’re happy with our heat-pump water heater, despite the cold climate and the fact that we don’t have a waste heat source in our basement. I’m guessing that, for half the year, we’ll save at least 60%, compared with a standard electric water heater, while only 10%–20% in the cold months. Homeowners with a waste heat source in their basements will do better.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-03-05 n/a 18301 Picking a Water Heater: Solar vs. Electric or Gas Is Just the Beginning

Why we opted for electric water heating over a solar water heater

Our GeoSpring heat-pump water heater. Click to enlarge.
Photo Credit: Alex Wilson

As we build more energy-efficient houses, particularly when we go to extremes with insulation and air tightness, as with Passive House projects, water heating becomes a larger and larger share of overall energy consumption (see Solar Thermal Hot Water, Heating, and Cooling). In fact, with some of these ultra-efficient homes, annual energy use for water heating now exceeds that for space heating—even in cold climates.

So, it makes increasing sense to focus a lot of attention on water heating. What are the options, and what makes the most sense when we’re trying to create a highly energy-efficient house?

Solar-electric vs. solar-thermal water heating

If we had built our new house three or four years ago, I suspect that solar water heating would have been included—or at least very seriously considered. But as costs of solar-electric (photovoltaic or PV) systems have dropped in recent years, more and more energy experts are recommending electric water heating, rather than solar thermal, and using PV modules to generate the electricity—so it’s still solar water heating, but not as direct.

Late-afternoon photo of the PV system on our barn--which is about 100 feet from the house.
Photo Credit: Alex Wilson

That’s what we have done at our new place. We realized in our planning that we had a great location for PV modules on our barn roof, but we didn’t have a good rooftop location for solar panels on the house. PV panels can be located farther away from where the energy is being used than can solar-thermal panels, because electrons can be easily moved fairly long distances through electrical cables, while piping runs for solar-thermal systems have to be much shorter.

Also, PV systems also don’t have any moving parts to wear out or that require maintenance; freeze protection isn’t a concern; and pressure build-up from stagnation in full sun (if a pump fails or during a power outage) can’t occur. So PV systems are very attractive from a long-term durability standpoint.

And if we’re generating our electricity from the sun why not use some of that electricity for water heating? That’s what we decided to do: install a PV system and heat our water with electricity

The GeoSpring offers several different control options: heat pump only, hybrid (both heat pump and electric resistance — less savings than heat pump only), boost (faster water heating and less savings than hybrid), standard (electric-resistance only — no energy savings), and vacation (maximum savings when homeowners are away). Click to enlarge.
Photo Credit: Alex Wilson

Electric water heating

So if one goes with electric water heating, what are the options? There are three primary choices:

  1. Conventional storage-type electric water heater. This is an insulated tank that holds 30 to 80 gallons, typically, and includes either one or two electric-resistance heating elements. Better storage water heaters have more insulation, so less stand-by heat loss occurs.
  2. Tankless water heater. A tankless, sometimes called on-demand or instantaneous, water heater heats the water as it is used. This offers the advantage of eliminating the stand-by loss that occurs with storage water heaters. Whole-house tankless water heaters are most commonly gas-fired, but electric models are also available.

    The problem with the latter is that they require a huge amounts of electricity. An electric tankless water heater large enough to supply a shower and another use at the same time will require a 60-amp or larger circuit at 220 volts. If a lot of homeowners were to switch to whole-house electric tankless water heaters, it would put a huge burden on the utility companies that have to meet peak demand—particularly in the morning when a lot of people are showering.

    There are other issues with tankless water heaters, including that they don't necessarily save energy.
  3. Heat-pump water heater. A heat pump water heater extracts heat out of the air where the water heater is located (typically a basement) to heat the water. Because the electricity is used to move heat from one place to another instead of converting that electricity directly into heat (as with electric-resistance water heating), the energy yield per unit of electricity input is much greater.

    We measure that efficiency as the “coefficient of performance” or COP—a COP of 1.0 is, in essence, 100% efficient at converting electricity at your site into heat. Most heat-pump water heaters have COPs of 2 to 3, meaning that for every unit of energy consumed (as electricity), at least two units of energy (as heat) are generated.

    (Note that if we consider “primary” or “source” energy instead of site energy, energy losses during power generation reduce that effective COP considerably.)
It's a little hard to read in this photo, but I love having the user instructions right on the water heater. Click to enlarge.
Photo Credit: Alex Wilson

Choosing a heat pump water heater

A heat-pump water heater is what we decided on for our house. We installed a 50-gallon GE GeoSpring model and, so far, we’re very happy with it. The GeoSpring is currently available only in a 50-gallon size, though rumors suggest that a larger, 80-gallon, model could be introduced. Because water heaters operating in heat pump mode take a long time to heat water, larger tanks typically make sense. If our two daughters were still in the house, a larger heat-pump water heater would have been more important.

One of the factors that attracted us to the GeoSpring is that it’s now being made in the U.S. GE had made its first-generation GeoSpring in Mexico, but moved that production to the U.S. two years ago.

The GeoSpring doesn’t have the highest performance of any heat pump water heater on the market, but the GeoSpring costs a third as much as the most efficient model. It’s also quieter. (See our GreenSpec section on heat pump water heaters for detail on all the most efficient models available.)

Next week, I’ll say a little more about heat-pump water heaters, including some issues with placement and implications of the fact that heat pump water heaters cool off the space where they are located—depending on the season, that can be an advantage or disadvantage.

Understanding heat-pump water heaters is important, as they will soon become the standard at least for larger electric water heaters—based on efficiency standards that take effect in mid-April 2015.

*                        *                        *

By the way, Eli Gould (the designer-builder of our home) and I will be leading a half-day workshop at the NESEA Building Energy Conference in Boston on Tuesday, March 4, 2014. In this workshop, “What Would the Founder of Environmental Building News Do? Adventures on the Cutting Edge of Green Building,” we’ll be reviewing product and technology choices, describing lessons learned, presenting data on performance, and discussing, in a highly interactive format, some outcomes from this project that can be applied much more affordably in deep-energy retrofits. This should be informative and a lot of fun. I’ll also be presenting in the main conference, March 5-6, on “Metrics of Resilience.”  Registration information can be found here.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-02-26 n/a 18253 Commissioning Our Home's Heat-Recovery Ventilator

To function properly, any ducted HRV has to be balanced after installation

Barry Stephens measuring the airflow through a ceiling register of our HRV.
Photo Credit: Alex Wilson

After choosing and installing our state-of-the-art heat-recovery ventilator (HRV), we completed a critical step in the installation of any HRV: commissioning, including the critical step of balancing the air flow.

This is absolutely necessary to ensure proper operation and full satisfaction.

Why commissioning is so important

The ducting runs in a ducted HRV system vary in their air-flow resistance. The two fans in an HRV should maintain neutral pressure—as much outgoing air force as incoming. Otherwise, with negative pressure in the house, radon and other soil gases could be drawn in, or with positive pressure, indoor air could be forced through the building envelope where it could cause moisture problems.

But beyond the two primary fans and pressure-balancing the entire house, the individual registers need to be balanced to ensure that you’re getting proper air flow through each of the supply and return registers. If this balancing step isn’t followed, the HRV might pull a lot more air out of a downstairs bathroom (which is closer to the HRV), for example, than a more distant upstairs bathroom.

The hand-held anemometer in a hood used to measure airflow.
Photo Credit: Alex Wilson

Balancing our Zehnder system

Barry Stephens, the business development and technology director at Zehnder America, came up to Vermont to commission and balance our Zehnder HRV. I didn’t watch the entire process, but was very impressed at the level of care that he gave to this task.

Barry used a hand-held device to measure airflow through the supply and return registers. This is a small hood that fits tightly over the register with an anemometer (wind gauge) allowing the airflow through the register to be measured in cubic feet per minute (cfm).

The flow through the registers (diffusers) can be adjusted in different ways depending on the type of register. Ceiling-mounted supply registers are adjusted simply by rotating the round, screw-mounted cover plate on the unit, which increases or reduces the gap and the airflow.

Measuring airflow through a wall register.
Photo Credit: Alex Wilson

Wall-mounted supply registers are adjusted by removing the cover plate and installing an insert that restricts airflow. Different-size disks can be added as needed to further restrict flow.

Exhaust ports are adjusted by moving the center component in or out.

After a round of adjusting, the airflow tests have to be repeated. Every time the flow through one register is changed it affects the airflow through the others. My sense is that there’s a lot of art involved in these adjustments; after balancing hundreds of systems, Barry and others at Zehnder America have a very good feel of how adjusting some diffusers will affect others.

I think for our system all this took several hours, though I’m sure I slowed Barry down with all my questions.

Condensate drain and controls

We realized before Barry arrived to commission our system that the condensate drain had never been hooked up during the installation. Zehnder HRVs have a sophisticated condensate drain with a specialized trap. Barry was able to carry out this installation quickly, though the fact that the trap hadn’t been installed over the previous several weeks meant that moisture got into the heat exchanger core, and this may have caused the frost protection system to work harder that it normally does, increasing electricity consumption.

While the user controls of the Zehnder ComfoAir 350 Luxe are elegantly simple, the behind-the-scenes controls are much more sophisticated—confirmed by paging through the 40-page installation manual (in English)—and I was very glad to be leaving the programming to Barry, though I’ll need to dig into those instructions when I want to change something.

We have two of these wireless controllers—one in each of our bathrooms.
Photo Credit: Alex Wilson

Experience to date

We commissioned the HRV the same day we set up an eMonitor energy monitoring system that allows us to track the electrical consumption of key loads in the house, including the HRV. While in normal operation the HRV uses very little energy, the intermittent frost-protection cycle does use a lot of energy—about 800 watts. During the last ten days of January (a very cold spell ), the unit used 65 kilowatt-hours (kWh), while this month (through February 16th) the unit has used 53 kWh.

I'm surprised at how high this consumption is and hope that some of it has to do with moisture having gotten into the heat exchanger core before the condensate drain was properly installed. I'll be very interested to see the annual consumption.

I love the simplicity of operating the HRV. From either bathroom I can either manually change the speed, or click on a clock icon to boost the unit up to the highest setting for either ten minutes (by tapping the button quickly) or 30 minutes by holding it down for three seconds. (Those times can be adjusted by going into the programming.)

As I noted last week, this isn’t the most affordable HRV you can get, but I feel very good about having what I believe to be the best and most energy-efficient model on the market.

*                        *                        *

By the way, Eli Gould (the designer-builder of our home) and I will be leading a half-day workshop at the NESEA Building Energy Conference in Boston on Tuesday, March 4, 2014. In this workshop, “What Would the Founder of Environmental Building News Do? Adventures on the Cutting Edge of Green Building,” we’ll be reviewing product and technology choices, describing lessons learned, presenting data on performance, and discussing, in a highly interactive format, some outcomes from this project that can be applied much more affordably in deep-energy retrofits. This should be informative and a lot of fun. I’ll also be presenting in the main conference, March 5-6, on “Metrics of Resilience.”  Registration information can be found here.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-02-18 n/a 18251 How We Chose Our Heat-Recovery Ventilator

Zehnder’s state-of-the-art HRV will provide years of service in providing fresh air with very low energy consumption.

Barry Stephens installing the condensate drain on our Zehnder ComfoAir 350 Luxe HRV. Click to enlarge.
Photo Credit: Alex Wilson

Balanced ventilation requires two fans: one bringing fresh air into the house and one exhausting indoor air (see 6 Ways to Ventilate Your Home). By balancing these two fans and the airflow through their respective ducts, the house is maintained at a neutral pressure—which is important for avoiding moisture problems or pulling in radon and other soil gases.

In a heat recovery ventilator (HRV) the two fans are in the same box, and they force air through a heat-exchanger core made of a corrugated plastic or aluminum. There are several types of heat exchanger cores in HRVs, and these effect efficiency and cost.

HRVs can have cross-flow heat exchangers or counter-flow heat exchangers. With cross-flow, the incoming and outgoing air streams are typically at 90° angles to each other. The heat transfer efficiency is good but not great: typically 50% to 70%.

With a counter-flow heat-exchange core, there is a longer pathway across which heat exchange occurs, so the efficiency is typically higher.

Zehnder's HRVs are larger than most, but that helps them achieve very low sound ratings and very high efficiency.
Photo Credit: Alex Wilson

Our Zehnder HRV

The HRV we installed in our new house is a Zehnder ComfoAir 350 Luxe. This is a Swiss-made, highly efficient HRV utilizing a counter-flow heat exchanger. In fact, testing by the Home Ventilating Institute (HVI) shows it to be the most energy-efficient HRV available. The American division, Zehnder America, is off to a rapid start, with about 800 installations in North America since its launch several years ago, according to Business Development and Technology Director Barry Stephens.

There are various ways to measure efficiency of HRVs. Apparent sensible effectiveness (ASEF) is the most commonly reported number for heat transfer efficiency. The HVI-listed ASEF of our Zehnder unit is 93%which is among the highest in the directory (though not quite the highest).

Another measure reported by HVI is the sensible recovery efficiency (SRE). This is a measure that corrects for waste heat from the fan motor that may be going into the incoming airstream, cross-flow leakage from the outgoing to the incoming airstream, and case leakage or heat transfer from the outside of the box to the airstream inside. These factors make it seem as if the heat transfer efficiency is higher than it really is; thus the SRE number is more accurate. With our Zehnder ComfoAir 350 the SRE is 88%—the highest that I found in the HVI Directory.

Zehnder's small-diameter ducting fits into 2x4 walls.
Photo Credit: Alex Wilson

In reviewing the HVI list of certified products, I found some other HRVs with higher ASEF values, such as a Broan-NuTone model with a listed ASEF of 95%, but that product had a SRE value of only 58%. With that product and most other HVI-listed models that have very high ASEF values, the SRE values are considerably lower, indicating that waste heat from high-wattage fan motors or other losses are boosting the ASEF values.

Another measure of efficiency is how much air is moved per unit of electricity consumed. Here we can look at the cubic feet per minute (cfm) of air flow per Watt of electricity consumption. With this metric, the Zehnder ComfoAir really shines, achieving a remarkable 2.58 to 3.25 cfm per Watt (depending on the fan speed). The Energy Star criteria for HRVs to be listed as EnergyStar is 1.0 cfm/W, and most good HRVs have air-delivery efficiencies only in the 1.0 to 1.5 cfm/W range. I was able to find only a few others with cfm/W values exceeding 2.0.

Zehnder ducting

Nearly as exciting as the superb energy performance of Zehnder HRVs is the ducting that is provided with them. The company produces ComfoTube ducting with a 3-inch outside diameter and 2.5” inside diameter. The outer surface is ribbed for strength and the inside smooth, for optimal airflow and quiet operation. The material is 100% high-density polyethylene, which is the most environmentally friendly plastic, in my opinion.

Ceiling-mounted exhaust port.
Photo Credit: Alex Wilson

The ducting diameter is small enough to fit in two-by-four interior walls. Because the airflow through the ducts is relatively low and sharp bends are eliminated, the airflow is very quiet. In fact, noise control is a key feature of all Zehnder products, and this is one reason the HRV itself is so quite large.

While some ducting systems for heating and ventilation are branched—with larger trunk ducts stepping down to smaller distribution ducts, Zehnder ComfoTube ducts are designed to be installed in a “home run” configuration—with a single, continuous duct extending from each supply and return diffuser all the way to the HRV. This feature also helps control noise, though it can make for a complicated spaghetti-like installation.

Three operation settings

Our HRV has three speeds, plus an extra-low “away” setting. Labeled 1, 2, and 3, the primary settings can be custom-set to deliver between 29 and 218 cubic feet per minute (cfm). As configured on our system, Setting 1 consumes 18-20 watts, Setting 2 consumes 30-35 watts, and Setting 3 consumes 80-85 watts. The Away setting uses just 7-10 watts.

Ceiling-mounted supply diffuser.
Photo Credit: Alex Wilson

There is a frost-protection cycle that goes on periodically in cold weather to prevent condensate from freezing in the heat exchanger core. This draws about 800 watts. The need for this can be greatly reduced by adding a ground-loop preheater. This circulates an antifreeze solution through a simple ground loop (tubing that can be buried along the house foundation during construction).


In my opinion, Zehnder makes the best HRVs and ERVs (energy-recovery ventilators) in the world. But you pay for that quality and performance. The system we have, a Zehnder ComfoAir 350 Luxe with ten supply ducts and ten return ducts, with their respective registers, and two remote controllers (for the upstairs and downstairs bathrooms) costs about $6,000. The geo-exchange loop, which we did not include, adds another $2,000.

While this is a lot to spend on ventilation, this integrated whole-house ventilation system obviates the need for separate bath fans, which can cost $300 to $600, installed, and some of that extra cost will be recovered over time through energy savings during operation, compared to standard HRVs.

Wall-mounted supply diffuser.
Photo Credit: Alex Wilson

The super-quiet, highly dependable operation is a nice bonus.

Next week I’ll talk about commissioning our HRV system.

*                        *                        *

By the way, Eli Gould (the designer-builder of our home) and I will be leading a half-day workshop at the NESEA Building Energy Conference in Boston on Tuesday, March 4, 2014. In this workshop, “What Would the Founder of Environmental Building News Do? Adventures on the Cutting Edge of Green Building,” we’ll be reviewing product and technology choices, describing lessons learned, presenting data on performance, and discussing, in a highly interactive format, some outcomes from this project that can be applied much more affordably in deep-energy retrofits. This should be informative and a lot of fun. Registration information can be found here.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-02-12 n/a 18231 6 Ways to Ventilate Your Home (and Which is Best)

How a green home really "breathes"

Should a green home require a piece of ventilation equipment like our Zehnder HRV?
Photo Credit: Alex Wilson

One of the features in our new house that I’m most excited about barely raises an eyebrow with some of our visitors: the ventilation system. I believe we have the highest-efficiency heat-recovery ventilator (HRV) on the market—or at least it’s right up there near the top.

But first, a lot of people may be wondering, should a "green" home require mechanical ventilation? A lot of people might think that this is just the kind of energy-consuming system that homes should be getting away from—while cracking windows for fresh air.

Why ventilate?

For centuries homes weren’t ventilated, and they did all right, didn’t they? Why do we need to go to all this effort (and often considerable expense) to ventilate houses today?

There are several reasons that ventilation is more important today than it was long ago. Most importantly, houses 100 years ago were really leaky. Usually they didn’t have insulation in the walls, so fresh air could pretty easily enter through all the gaps, cracks, and holes in the building envelope.

Also, the building materials used 100 years ago were mostly natural products that didn’t result in significant offgassing of volatile organic compounds (VOCs), formaldehyde, flame retardants, and other chemicals that are so prevalent in today’s building materials, furnishings, and other stuff.

Ventilation options

Ventilation can take many different forms. Very generally, systems can be categorized into about a half-dozen generic types:

  1. No ventilation. This is almost certainly the most common option in American homes. There is no mechanical system to remove stale indoor air (and moisture) or bring in fresh outside air. In the distant past, when buildings weren’t insulated, this strategy worked reasonably well—relying on the natural leakiness of the house. It’s worth noting, though, that even a leaky house doesn’t ensure good ventilation. For this strategy to work there has to be either a breeze outside or a significant difference in temperature between outdoor and indoors. Either of these conditions creates a pressure difference between indoors and out, driving that ventilation. On calm days in the spring and summer, there might be very little air exchange even in a really leaky house.
  2. Natural ventilation. In this uncommon strategy, specific design features are incorporated to bring in fresh air and get rid of stale air. One approach is to create a solar chimney in which air is heated by the sun, becomes more buoyant, and rises up and out through vents near the top of the building; this lowers the pressure in the house, which draws fresh air in through specially placed inlet ports. Many homeowners may think of opening windows as part of their ventilation strategy, but most people only open windows in the summer—if at all—and because of the pressure differential issue just mentioned, open windows don't guarantee good air exchange.
  3. Exhaust-only mechanical ventilation. This is a relatively common strategy in which small exhaust fans, usually in bathrooms, operate either continuously or intermittently to exhaust stale air and moisture generated in those rooms. This strategy creates a modest negative pressure in the house, and that pulls in fresh air either through cracks and other air-leakage sites or through strategically placed intentional make-up air inlets. An advantage of this strategy is simplicity and low cost. A disadvantage is that the negative pressure can pull in radon and other soil gases that we don’t want in houses.
  4. Supply-only mechanical ventilation. As the name implies, a fan brings in fresh air, and stale air escapes through cracks and air-leakage sites in the house. The air supply may be delivered to one location, dispersed through ducts, or supplied to the ducted distribution system of a forced-air heating system for dispersal. A supply-only ventilation system pressurizes a house, which can be a good thing in keeping radon and other contaminants from entering the house, but it risks forcing moisture-laden air into wall and ceiling cavities where condensation and moisture problems can occur.
  5. A ventilation system schematic from the Building Science Corporation fact sheet on balanced ventilation. Click to enlarge.
    Photo Credit: Building Science Corp.
    Balanced ventilation. Much better ventilation is provided through a balanced system in which separate fans drive both inlet and exhaust airflow. This allows us to control where the fresh air comes from, where that fresh air is delivered, and from where exhaust air is drawn. Balanced ventilation systems can be either point-source or ducted. With ducted systems, it makes sense to deliver fresh air to spaces that are most lived in (living room, bedrooms, etc.) and exhaust indoor air from places where moisture or pollutants are generated (bathrooms, kitchen, hobby room).
  6. Balanced ventilation with heat recovery. If there are separate fans to introduce fresh air and exhaust indoor air, it makes a lot of sense to locate these fans together and include an air-to-air heat exchanger so that the outgoing house air will precondition the incoming outdoor air. This air-to-air heat exchanger—more commonly referred to today as a heat-recovery ventilator or HRV—is the way to go in colder climates. A slightly different version, known as an energy-recovery ventilator (ERV), is similar but transfers moisture as well as heat from one airstream to the other, keeping more of the desirable humidity in the house in the winter and reducing the amount of humidity introduced from outdoors in the summer.

I’m a firm believer that all homes should have mechanical ventilation. With better-insulated, tighter homes that ventilation is all the more important. But even in a very leaky house, one can’t count on bringing in much fresh air or calm days in the spring and fall when there isn’t a pressure differential across the building envelope.

If budgets allow, going with balanced ventilation is strongly recommended, and if you’re doing that in a relatively cold climate, like ours, then providing heat recovery is a no-brainer. Mechanical ventilation always takes energy; with heat recovery the energy penalty of fresh air is minimized.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-02-05 n/a 18145 Cold Weather Tests the Limits of Our Mini-Split Heat Pump

Testing the limits of the air-source heat pump in our new house with this cold weather

The interior unit of our Mitubishi air-source heat pump. Click photos to enlarge.
Photo Credit: Alex Wilson

It’s been pretty chilly outside. A number of people have asked me how our air-source heat pump is making out in the cold weather. I wrote about ths system last fall, well before we had moved in to our new home. Is it keeping us warm?

First, if you want to get up to speed on the surprising and counterintuitive nature of how an air-source heat pump works, check out our primer on the topic—which includes a great diagram.

We’ve only been living in the house for a few weeks, but so far, so good. Our 18,000 Btu/hour Mitsubishi mini-split heat pump (MSZ FE18NA indoor unit and MUZ FE18 outdoor unit) is doing remarkably well in keeping us comfortable. We don’t have any oil or gas heating in the house, only the electric heat pump and a small wood stove that we’ve fired up twice so far.

The indoor heat pump unit is mounted on a wall next to our kitchen, and it’s been operating pretty steadily in this cold weather. (Even though we’ve heated with wood for decades and have all the wood we could ever use, I’ve been curious how the house will do just on electricity, so have refrained from using the wood stove.)

A thermometer in a bookcase on an outside wall diagonally across the kitchen-dining-living space from the heating unit is reading 66°F as I write this, with the outside temperature about 12°F. A thermometer in our upstairs bedroom read 70° when I got up this morning, and has typically been about 68°—and remarkably uniform.

Interior unit placement on a kitchen wall.
Photo Credit: Alex Wilson

When the mercury dropped to –6°F a few days ago, the house got colder. I saw one reading on the outside wall downstairs as low as 61°F and our bedroom got down to about 65°F. It was chilly enough that I fired up our small wood stove for the first time, and that fairly quickly raised the downstairs temperature to a comfortable 68°F. With our tight construction there are few drafts.

Monitoring our energy consumption

We have an eMonitor (made by PowerWise Systems of Blue Hill, Maine) installed to track the home’s overall electrical consumption as well as the consumption of a number of individual loads. The monitor has clips that clamp onto different circuits in the electrical panel as well as the electrical main coming into the panel, and it somehow measures electricity flow through those cables. We’re tracking consumption separately for our heat pump heating system, our heat-pump water heater, and our heat-recovery ventilator.

Most of the time the air-source heat pump has been drawing about 2,500 watts, with very brief spikes up to about 3,400 watts (I suppose those spikes occur when a pump or fan kicks on). To put this in perspective, the 2,500 watts in the standard heating mode is about twice what our KitchenAid toaster draws (1,200 watts), though of course the toaster operates for only short periods of time.

So far we haven't had to do any snow clearing from the outdoor unit, but in a heavy snow we likely will have to.
Photo Credit: Alex Wilson

Since we hooked up the eMonitor and started collecting data (five days ago), our Mitsubishi heat pump has used 221 kWh of electricity—during a fairly cold stretch. This is about what the entire solar-electric system on our barn cranked out during this period—and roughly three times the output of that portion of our PV system allocated to the house. (It’s a “group-net-metered” system, with two-thirds of the output going to neighboring homes.)

It will be interesting to look at this data over the course of months and years to see how the electricity consumption averages out over time and  how that compares to our solar production.

Heat distribution with point-source heating

Because our heat source is on a downstairs wall, I had been very curious how effectively heat would be distributed throughout our 1,600-square-foot house. The main kitchen-dining-living space keeps a fairly even temperature in the high-60s. A downstairs study or guest room at the far corner of the house and separated from the heat pump by a hallway and doors (with the door open) stays a little cooler, though watching a movie there last night was fine with a sweater.

Upstairs, the our bedroom on the north side of the house has maintained a remarkably constant 68-70°F on all but the coldest nights. When the outside temperature dipped to minus-6°F, our bedroom dropped to the mid-60s. Last night, with the outside temperature down to 7.5°F, we actually closed our door to keep the bedroom a bit cooler, and the temperature dropped from 70°F to 67.8 by morning.

The open stairwell does a great job at distributing heat upstairs. Our north bedroom stays 68-70°F.
Photo Credit: Alex Wilson

I don’t have a thermometer in the south bedroom, which is being used as a home office by my wife, but it feels about the same. There are two double-hung windows instead of a single casement window, so there is certainly more air leakage, but there is also solar gain through those windows.

Bottom line

All in all, we are very satisfied with the air-source heat pump. It works well, in large part, because our house is so energy efficient. This is a superb heating option (and cooling, by the way) for a house with a very well-insulated building envelope. Once we install the low-e storm windows on the double-hung windows on the south and east sides of the house, we should do somewhat better. (With our superinsulated house, the south and east windows are a weak point, both relative to air leakage and R-value.)

And on a cost per delivered Btu basis, with the air-source heat pump we’re spending just 58% of what we would spend on oil heat (assuming an Energy Star oil boiler operating at 83% efficiency with #2 heating oil at $3.91 per gallon vs. electric heat in an air-source heat pump with a coefficient of performance of 2.25 and electricity costing 15¢/kWh). (You can plug in your own assumptions and compare fuels on BuildingGreen’s online calculator.)

A summary of energy consumption in our house over the past week with this cold weather. The HRV had to work harder than it generally should due to moisture that got into it before we hooked up the condensate drain. Click to enlarge.
Photo Credit: eMonitor data from Alex Wilson

Plus, on an annual basis we should be producing as much electricity with solar as we consume—net-zero-energy. So we’re pretty happy. Warm and happy.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-01-29 n/a 18139 On the Benefits of Online Learning

With a new group of online BAC courses starting this week, I’m reminded of the benefits of learning—and teaching—from home.

San Francisco Bay Area traffic. Click to enlarge.
Photo Credit: Getty Images

Truth be told, I was slow warming up to online instruction. Ten years ago, in early 2004, BuildingGreen was approached by Boston Architectural College (then Boston Architectural Center—but with the same acronym BAC) about collaborating on sustainable design curriculum. There is so much value in face-to-face instruction and student interaction, I thought, how could online instruction take its place?

But we did collaborate, helping BAC develop it’s Sustainable Design curriculum. And I created and for a number of years taught one of the foundation online courses for the program: “Sustainable Design as a Way of Thinking,” which is now being taught by my friend David Foley.

This assemblage of courses, now housed in BAC’s Sustainable Design Institute, offers the most comprehensive, accredited online instruction in sustainable design anywhere. There are nearly three dozen courses offered that can be taken as continuing education courses by anyone, taken as part of graduate degree programs, or taken as electives as part of a relatively new MDS (Masters in Design Studies) program in Sustainable Design that is now in its third year.

Pros and cons of online instruction

I’m teaching a brand new course in the BAC Sustainable Design Institute, Resilient Design, that starts this week, so I’ve been focusing actively on online instruction and its various advantages and disadvantages. There still is the disadvantage of not being able to engage students in the classroom—responding in person to questions and perspectives that come up, having eye-contact with students, etc.

But the online discussions can be dynamic, as I learned years ago with my first online teaching. And there are ways to encourage active participation by students that BAC has become very good at.

Beyond the pedagogy of instruction, however, online education has some significant environmental advantages.

The big benefit is less driving. I can teach from my home in Vermont, and students can participate from all over. In my Resilient Design course, I have students from California, Florida, Massachusetts, Missouri, Oregon, Texas, Washington State, and Alberta, Canada. In other courses I’ve taught students have enrolled from as far away as Iraq and Japan.

Even when students and faculty live close-by, commuting energy can be huge. In 2009, I participated in an exercise of figuring out how Antioch New England in Keene, New Hampshire, could become a carbon-neutral university, and I was astounded at what a huge percentage of the university’s total carbon emissions resulted from student and staff commuting—over two-thirds as I recall.

Better online teaching tools make learning from afar better

Until I started this new Resilient Design course it had been five or six years since I had taught an online BAC course. In more recent years BAC has been using Moodle, which is a great platform.

I used to simply post lectures as static PowerPoint presentations, but now I’m using a package called VoiceThread to add audio commentary and even highlight items in the slides that I’m talking about. I’m very excited about the capability VoiceThread offers.

As with Blackboard, Moodle has extensive online discussion capabilities, including the “Coffeehouse” forum. I’m looking forward to dynamic conversations there—which I can take part in with my feet up and a cup of tea (I’m not a coffee drinker) on the windowsill of my new house.

BAC course offerings

Unfortunately, my Resilient Design course is now filled up, but it should be possible to still sign up for most of the other 13 eight-week courses that started on Tuesday of this week. Included are courses in residential energy modeling, green roofs, materials and indoor air quality, sustainable design and preservation, sustainable transportation, the economics of green building, and zero-energy homes.

And I’m sure we’ll be repeating the Resilient Design course, so keep an eye out for future offerings of that.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-01-21 n/a 18131 Look Under the Sea for Safe Nuclear Waste Storage
Workers entering the Yucca Mountain nuclear waste storage facility in 2006.
Photo Credit: Isaac Breekken, AP

With nowhere on land to turn, we should look under the seabed for places to bury high-level nuclear waste

For more than 30 years the nuclear industry in the U.S. and nuclear regulators have been going down the wrong path with waste storage—seeking a repository where waste could be buried deep in a mountain. Nevada’s Yucca Mountain was the place of choice until…it wasn’t.

Any time we choose to put highly dangerous waste in someone’s backyard, it’s bound to cause a lot of NIMBY opposition, even in a sparsely populated, pro-resource-extraction place like Nevada, and in the case of Yucca Mountain, powerful Nevada senator Harry Reid has hardened that opposition politically.

Aside from NIMBYism, the problem with burying nuclear waste in a maintain (like Yucca Mountain) or salt caverns (like New Mexico’s Carlsbad Caverns—an earlier option that was pursued for a while in the 1970s) is that the maximum safety is provided at day one, and the margin of safety drops continually from there. The safety of such storage sites could be compromised over time, due to seismic activity (Nevada ranks fourth among the most seismically active states), volcanism (the Yucca Mountain ridge is comprised mostly of volcanic tuff, emitted from past volcanic activity), erosion, migrating aquifers, and other natural geologic actions.

A better storage option

I believe a much better solution for long-term storage of high-level radioactive waste is to bury it deep under the seabed in a region free of seismic activity where sediment is being deposited and the seafloor getting thicker. In such a site, the level of protection would increase, rather than decrease, over time.

In some areas of seabed, more than a centimeter of sediment is being deposited annually. Compacted over time, such sediment deposition could be several feet in a hundred years, and in the geologic time span over which radioactive waste is hazardous, hundreds to thousands of feet of protective sedimentary rock would be formed.

The oil and gas industry—for better or worse—knows a lot about drilling deep holes beneath a mile or two of ocean. I suspect that the deep-sea drilling industry would love such a growth opportunity to move into seabed waste storage, and I believe the Nuclear Regulatory Commission (NRC) or other agencies could do a good job regulating such work.

The waste could be placed in wells extending thousands of feet below the seabed in sedimentary rock in geologically stable regions. Let's say a 3,000-foot well is drilled beneath the seabed two miles beneath the surface of the ocean. Waste could be inserted into that well to a depth of 1,000 feet, and the rest of the well capped with 2,000 feet of concrete or some other material. Hundreds of these deep-storage wells could be filled, capped, and such a sub-seabed storage field designated as forever off-limits.

Three Mile Island Power Plant.
Photo Credit: Sandia National Laboratory

Industry or the Department of Energy (working in concert with the United Nations, if this option were purused in international waters) would have to figure out how to package such waste for safe handling at sea since the material is so dangerous, but I believe that is a surmountable challenge.

For example, radioactive waste is already often vitrified (incorporated into molten glass-like material) to reduce leaching potential for dry-cask storage, and such casks could be tagged with radio-frequency emitters so that any lost containers could be easily recovered with in the event of such accidents.

Take a look at how much money taxpayers and industry have already poured into Yucca Mountain: about $15 billion by the time the Obama Administration terminated federal funding for it in 2010, according to Bloomberg News—and the estimates for how much more it would take to get a working waste storage facility of that sort operational had risen to about $96 billion by 2008, according to the U.S. Department of Energy at the time. I believe that sub-seabed storage would be far less expensive.

Should nuclear power be part of our energy future?

I used to be a firm opponent to nuclear power, and I am still opposed to the form of nuclear power we have today. But my position is softening. Should nuclear power plants be developed that have failsafe, passive cooling systems that would prevent a meltdown even if sabotaged from the inside, if the economics of such plants could work, and if we can shift to safer long-term storage, I could get behind a rebirth of the nuclear power industry.

Those are big “ifs” and I have doubts that they will be satisfied, but I recognize that nuclear power is largely free of carbon emissions—unlike natural gas, oil, and, especially, coal. We need to dramatically reduce carbon emissions if we are to prevent catastrophic global warming, according to leading scientists.

A starting point for the nuclear industry in building new support for nuclear power should be reexamining sub-seabed waste storage, which could be far safer and far less expensive than other approaches being focused on most actively today.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-01-15 n/a 18119 Stay Safe When Using Space Heaters and Wood Stoves

Cold weather, when wood stoves are cranked up and portable electric space heaters are brought out of the basement and plugged in, is when most house fires occur

Enjoying a wood stove on a cold winter day.
Photo Credit: Alex Wilson

The morning paper had yet another story about a destructive house fire—fortunately no fatalities (this time*), but the total loss of another home and another family’s belongings. And like many others, the culprit appears to have been the wood stove.

So many of the home fires we experience in Vermont result from trying to keep warm. Some have to do with faulty installation of wood heating equipment; many others result from improper operation of that equipment or management of the ash.

Burning wood safely

Having used a wood stove as a primary heating source for over 30 years, I’m pleased to report that I have never had problem, though evidence in both the house we’re moving out of and our new (old) house shows that other occupants have dealt with fires on multiple occasions. In fact, based on extensive charred wood I’ve found around the chimneys, it’s very lucky that either house is still standing.

There’s a reason that building codes call for specific set-backs from combustible materials and require insulated flue pipe wherever it extends through building components. With any installation of a wood stove, pellet stove, or any other wood-burning equipment, follow manufacturer recommendations carefully to ensure safe operation. (To choose an efficient, clean-burning wood or pellet stove, see our recommended products in GreenSpec.)

On the safe-operation front, a good starting point is to burn only well-seasoned wood. (I admit to a track record that hasn’t always been great in this department.) With dry wood, there will be less need to operate the wood stove with the door ajar an less need to open it up to adjust the logs during operation—both potential risks.

A big part of burning wood is about storing firewood. If, like a lot of people, you have a wood shed for storing the bulk of your wood outdoors and bring in smaller amounts for storage near the wood stove, pay attention to setback from the stove and excessive accumulation of bark and detritus near the wood stove that could catch fire from a wayward ember.

A wood stove installation without the dogs.
Photo Credit: Vermont Castings

Managing ashes

Most of the wood-heat-related fires that friends of mine have dealt with have to do not with the wood stove itself, but with ashes. My wife and I store the ashes that we remove from our wood stove in several metal trash cans, and then periodically we scatter those ashes on our garden and fields. We have enough storage that we typically spread the ashes only once a year—in the spring or fall.

An experience last year showed me just how risky spreading ashes can be. I must have run out of ash storage capacity so had to spread some ashes in the spring when we were still using the wood stove. I spread ashes that I had removed from the wood stove weeks earlier, so I hadn’t thought there could possibly be hot coals, but after scattering a number of shovelfuls I noticed some threads of smoke from the grass where ashes had been spread.

I was easily able to deal with the few hot embers using patches of snow that remained on the ground, but it reminded me just how long coals can stay hot when buried in ashes. I’m almost sure those ashes had been in the ash can for at least two weeks.

Other fire risks in cold weather

It isn’t only wood heat that creates a fire risk. Gas- and oil-fired furnaces and boilers can also malfunction, and that happens more commonly in the coldest weather when they are working the hardest.

Cold weather is also when homeowners are likely to use portable electric space heaters. These can overload electrical circuits or result in shorts in the power cord, particularly if the cords are very old or damaged by pets or abrasion. Every year I hear about fires caused by electric space heaters. Examine the cords to those heaters carefully and replace as needed.

In very cold weather we also sometimes hear about homeowners who use a kitchen oven for heat. Whether gas or electric, ovens should never be used for space heating; they aren’t designed for it. When gas ovens (propane or natural gas) are used for space heat, they also introduce combustion products to the house—and all open combustion of gas introduces a lot of water vapor, which can be a problem in some situations. (I actually discourage all open combustion in houses—i.e., gas ranges, cooktops, and ovens—but the indoor air quality issues are much greater when those appliances are used for heating.)

Energy conservation is always safe

Generating heat to create warmth nearly always carries some risk. But reducing the need for supplemental almost never does.

Improved insulation, plugging holes in the building envelope, tightening up leaky windows, and other energy conservation improvements are the best strategies for ensuring safety in houses in cold weather.

Not only are superinsulated houses safer from fire because they require less heat to keep warm, but they are also safer in the event of power outages or interruptions in heating fuel—the resilience argument I’m always making (see Resilient Design: 7 Lessons from Early Adopters). You’ll remain comfortable longer if you can’t operate your heating system, and if you do need to operate a separate space heater, it will be for a shorter period of time.

Safe is good. And conserving energy is the best way to achieve that safety.

* The morning this article came out in our local paper, the front page of that paper had a story of a tragic house fire in my home town of Dummerston in which two people died. No word yet on the cause of the fire, but I suspect it will prove to be heating related.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2014-01-08 n/a 18102 My Green Policy Wishlist for 2014


Six items on my policy wish-list for 2014 and beyond.

Safe bicycle commuting and walking is high on my wish list for 2014.
Photo Credit: Yuba Cargo Bikes

It's fun for me to dream about stuff—building products and materials—and how we can make that stuff greener. I recently wrote about 7 wish-list items for greener building products and materials. Today I want to talk policy—six changes we need in the public sphere to bring more sustainability to our built environment and beyond.

1) Strengthen building codes by recognizing resilience

I believe that the need for buildings and communities that can withstand heat waves, more intense storms, flooding, drought, and other effects of a changing climate—as well as problems wrought directly by our fellow humans (like terrorism)—point to the need for strengthening building codes and land-use regulations.

Resilience can be the motivation for codes and standards that will ensure more sustainable, energy-efficient, comfortable, and livable buildings and communities. New York City, in implementing 16 of the 33 recommendations coming out of the Building Resiliency Task Force in 2013, has demonstrated the potential for moving forward quickly with change. 2014 can be the year for other municipalities to make similar progress.

2) Account for societal impacts in pricing energy then rely on the free market

When we fuel up our cars, turn up our thermostat at home, or leave our lights on, that energy consumption affects everybody: air pollution that causes health problems, water pollution from fossil fuel extraction, hazardous disposal of byproducts such as coal fly ash and radioactive waste, military costs of protecting our access to that energy, and global warming impacts of carbon dioxide emissions. These societal costs of energy consumption should be quantified and factored into the price we pay for those fuels.  

PV system at Nellis Air Force Base.
Photo Credit: U.S. Air Force

Whether through carbon taxes, a new cap-and-trade approach with air and water pollution, new waste-disposal fees, or some other mechanism, by making consumers and businesses pay more for the consumption of energy sources that result in significant societal impacts, a huge incentive could be provided for energy conservation and renewable energy production. Such taxes or fees could even be levied in a revenue-neutral way through “tax shifting”—offsetting, for example, payroll taxes.

If we had the wisdom and courage to do this, we could then let market forces do their magic in fueling innovation and product development and energy performance. It’s a long shot, I know (I’m not holding my breath), but I’m wishing for recognition of this market-based approach to energy pricing in 2014.

3) Build political momentum for transportation alternatives

The automobile rules in America—at the expense of investment in public transit and infrastructure enhancements that would benefit walkers and bicyclists. Changing this paradigm would create better places to live—where you could safely walk to a corner café or enjoy a comfortable bus or rail commute to work. Yet, in Washington, these alternatives to the automobile are considered fringe special interests.

My wish for the New Year is a change in attitude about these alternatives to the automobile. Some of our major cities, from Philadelphia to Portland, Oregon, are making tremendous progress along these lines, but change needs to come to the rest of the country, where pedestrian safety is just as important as in Portland. In our small town of Brattleboro, we’ve just experienced the fourth pedestrian fatality in two years!) I believe that once more people see and experience the benefits of non-automobile transportation, momentum will build for even more rapid change—but we have a long way to go.

4) Institute financing mechanisms for energy improvements and renewable energy

Innovative financing mechanisms to make private investments in energy efficiency and renewables more affordable are needed if we are to achieve rapid progress in improving the energy performance of existing homes and businesses. PACE (Property Assessed Clean Energy) financing is an option that is being tried in some places, but there has been significant pushback, due to concerns about who’s first in line for recovery of debt in the event of a default. I think PACE can work effectively (Vermont, in fact, has instituted regulations that address most of the concerns of mortgage lenders), but we shouldn’t stop there.

In 2014 I’d like to see the creative minds of the banking industry, investment community, electric and gas utilities, and even the insurance industry come up with new financing mechanisms for energy improvements. Government probably has a role in this, whether through loan guarantees, accelerated depreciation regulations, or other mechanisms.

PV system going in at Leonard Farm in Dummerston, VT.
Photo Credit: Alex Wilson

5) Extend producer tax credits and other incentives for renewables

Assuming that we don’t make progress in imposing taxes on the societal impacts of conventional energy consumption so that we can put market forces to work (my first choice—see above), I’d like to see extension of some (but not all) of the subsidies and incentives that support renewables. At the commercial power production level, developers of wind and solar farms benefit from producer tax credits. These are good and should be extended, while most incentives for corn-based ethanol don’t make sense.

Homeowners benefit from tax credits for solar energy systems and a few other energy technologies. Most of these should also be extended, though perhaps at gradually dropping levels as the prices for these systems (and thus the need for subsidy) diminish.

I do think, however, that there should be a cap on the solar tax credits (we don’t need to be subsidizing Aspen billionaires putting in massive solar arrays to melt snow on their driveways). And some of the other tax credits should be reevaluated—such as support for ground-source (geothermal) heat pumps that cost a whole lot more than their air-source heat pump cousins and residential-scale wind turbines that usually aren’t cost-effective.

Most renewable energy credits are due to expire in the next few years. We should take action now to extend these to keep the renewable energy industry strong and maintain the pace of progress. It isn’t fair to the industry to wait until the last minute in passing extensions to such programs, as has been common practice in the past.

6) Make frugal cool

Finally, I’d love to see frugality celebrated in the U.S. instead of only celebrating excess—as seems to be the case in the popular media and advertising world today. When my neighbor insulates her house or buys a plug-in hybrid car I benefit from the reduced energy consumption and pollution. We should build a culture of recognizing and expressing gratitude for conserving energy.

Happy New Year.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.



2014-01-02 n/a 18043 7 Green Building Wishes for 2014

Here are some green product developments I’d like to see in the New Year

A plug-in hybrid vehicle charged using a net-metered PV array at the Philadelphia Navy Yard. I want to see the market share of plug-in vehicles double next year. Click to enlarge.
Photo Credit: Alex Wilson

I spend a lot of time writing about innovations in the building industry—the cool stuff that’s coming out all the time. But I also like to think about what’s needed: stuff that’s not (yet) on the market or performance levels not yet available.

1) Rigid insulation with no flame retardants and insignificant global warming potential

We've been highly critical of the brominated and chlorinated flame retardant chemicals added to nearly all foam-plastic rigid insulation today as well as the high-global-warming-potential blowing agents used in extruded polystyrene (see Can We Replace Foam Insulation?). I would love to see affordable alternatives. They could be new formulations of polystyrene or polyisocyanurate that doesn’t require flame retardants or inorganic materials that are inherently noncombustible (see our review of cool new products from Greenbuild for some advances). I’m intrigued by advanced ceramics and could imagine a foamed ceramic insulation being developed that meets these criteria.

2) A really good exterior insulation system for existing houses

We need to dramatically improve the energy performance of existing houses (see The Challenge of Existing Homes: Retrofitting for Dramatic Energy Savings), and one important strategy for doing that is to carry out “deep energy retrofits” by adding a thick layer of rigid insulation on the exterior and installing window surrounds to extend the window openings out to the new outer plane. The easier and cheaper we can make this addition the better, as long as we adequately provide for air leakage control, drying potential, and other aspects of building science. This calls for a really good system—perhaps some or all of it prefabricated.

Window surround used with our deep-energy retrofit in which exterior insulation was added to the wall. We need to develop simpler, less expensive options.
Photo Credit: Alex Wilson

3) Even better air-source heat pumps for cold climates

I’ve written frequently about the tremendous innovation we’ve seen in the world of air-source heat pumps, particularly the minisplit systems from such companies as Mitsubishi, Daikin, and Fujitsu. The Mitsubishi unit we recently installed kept our new house toasty with the temperature dipping to –5°F last week, and it should be fine down to –13°F. But I’d like to see operability down to –20. I’d also like to see affordable air-to-water heat pumps that can deliver high enough temperatures to be effective for baseboard hot water (hydronic) heating.

4) Affordable, durable LED lighting at 100 lumens per watt and a CRI of 90

There have been dramatic improvements in LED (light-emitting diode) lighting in the past few years, but we need more improvement if the market share of LEDs is to surpass that of incandescent and compact fluorescent lighting. I’d like to see LED lights delivering 100 lumens of light per watt of electricity consumption while producing light quality comparable to that of incandescent light bulbs (color rendering index or CRI of 90 or higher), with heat management technology good enough that manufacturers can provide a five-year warranty—and all this at an unsubsidized retail price of $5 or less. I think all that will be doable soon.

5) Affordable options for delivering emergency power from solar-electric systems

2013 saw the introduction of the first inverter for grid-connected solar-electric (PV) systems that allows electricity to be delivered during the daytime when the grid is down (the vast majority of grid-connected PV systems can’t do this—see Islandable Solar—PV For Power Outages). We installed one of these at our new place. But when a battery system is added to a grid-connected PV system so that electricity can be delivered to critical-load circuits, the cost usually goes up by $10,000 or more. I’d like to see the brightest engineers put their efforts into bringing the cost of this down to what would be spent for a good-quality, whole-house generator (about $5,000). Today’s batteries are expensive, so this goal will be a challenge, but I think there would be strong demand for such a system.

The new Cree Bulb in high-color-rendering True White. While relatively affordable through Home Depot, costs need to drop further if LEDs are to capture significant market share.
Photo Credit: Cree

6) Technology to deter birds and bats from wind turbines

I’m a huge fan of wind power, but I remain troubled by news of bird and bat fatalities (see Utility Fined for Eagle Deaths Linked to Wind Turbines). It should be possible to develop systems that somehow warn off birds and bats. Perhaps high-frequency sound could be generated—too high-pitched for our ears—but noisy to birds and bats who get close. High-frequency noise tends to attenuate quickly, so perhaps such acoustic systems wouldn’t affect nearby residents.

7) 100% growth in plug-in electric vehicles

I believe that plug-in electric and hybrid gas-electric vehicles are among the most important innovations the automotive industry ever. They offer the potential not only for renewable energy sources to power our vehicles, but also the potential to dramatically change our power grid—with those battery systems stabilizing the grid and helping utility companies better manage supply and demand. Toward this end, I’m hoping to see 100% growth in plug-in hybrid and all-electric vehicle sales in 2014. That sounds like a lot, but doubling a small number is not unreasonable.

I won’t get all of these wishes in 2014, but perhaps we’ll make significant progress on some of them. We’ll all be the better for it.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-12-26 n/a 18035 NIMBYism Alert: Opposition to "Industrial" Solar Projects

Are we going to find the same NIMBY opposition to larger solar systems that we’re experiencing today with wind farms? 

The 197 kW solar array at Logan Airport in Boston—on the top level of the Terminal B parking garage. Click to enlarge.
Photo Credit: Alex Wilson

When the economy-of-scale with wind power led to larger and larger wind turbines, opponents of these installations took to referring to them as “industrial wind power.” Whenever I see a letter-to-the-editor or news story that uses this identity I can tell that it’s going to have an anti-wind bias.

Whether its marring their views of pristine mountains, blighting their night sky with blinking red lights, causing bird and bat fatalities, or producing “infrasound” pollution, opponents almost universally refer to these wind farms using an industrial moniker.

So, I’m becoming troubled by recent reference to “industrial solar” in describing the larger photovoltaic (PV) installations that are cropping up in Vermont and nationwide. Some opposition seems to be emerging, for example, to a 2 megawatt (MW) array that’s being proposed for Brattleboro, and I’m hearing more and more such concerns nationally.

The economy of scale with solar

The 14.2 MW solar array at the Nellis Air Force Base in Nevada provides a quarter of the facility's power demand.
Photo Credit: Robert Valenca, USAF

As with wind, there is an economy-of-scale with solar-electric systems. Bulk purchase of solar modules brings the costs down somewhat and, more significantly, larger inverters (the devices that convert direct-current electricity produced by PV modules into the alternating current that can be fed into the utility grid) and other balance-of-system components are a lot less expensive per kW or MW of capacity than the residential-scale components being installed for home systems.

But the differences in cost between large and small systems aren’t nearly as great with PV systems as they are with wind turbines. This means that the incentives for building very large solar systems (“industrial-scale” if you must) aren’t as great as they are with wind.

Advantages of smaller PV systems

Despite the (relatively minor) economy-of-scale that argues for larger PV systems, there are some benefits of small systems.

Close-up of the tracking PV modules at the Nellis Air Force Base.
Photo Credit: USAF

For starters, small systems are well-suited to rooftops. A typical house, if it has a reasonable orientation, can hold a 4-6 kW solar array, enough to handle a significant fraction of the home’s power consumption (as long as then home is reasonably energy-efficient). And commercial buildings, with large flat roofs can often hold hundreds of kW or even a MW or two of solar—which can provide a significant fraction of those buildings’ electrical demands.

Putting solar modules on roofs creates headaches with roof maintenance, and poor-quality installations sometimes result in roof leaks, but rooftop mounting allows us to preserve land area for agriculture, recreation, and wildlife habitat. Whenever possible, I prefer to see PV systems installed on rooftops or carports rather than ground-mounting, though I recognize that that isn’t always possible or practical.

Small PV systems also usually generate electricity close to where it is being consumed. Such “distributed power” is changing the face of the utility grid. From a resilience standpoint, generating power close to the point of end-use of electricity also opens up an opportunity for incorporating either some battery storage or specialized inverters with capability to draw power from the solar system even when the grid is down—something that most grid-connected solar systems can’t do today. (For more on that, refer back to Beating the Achilles Heel of Grid-Tied Solar-Electric Systems.)

A rooftop 2 MB solar array at the Schüco U.S. headquarters near Hartford, CT.
Photo Credit: Alex Wilson

Is big solar bad?

Not in my book. As I look toward the future and a growing imperative to dramatically reduce our fossil fuel consumption and carbon dioxide emissions, I’m convinced that we need a mix of facility sizes with renewable energy systems. There will be many places where large, ground-mounted multi-megawatt-scale solar systems make sense, such as along highways and utility corridors where the land is already degraded and agriculture may not be feasible.

In arid places with lots of open land, such as the American Southwest, it should be possible for large solar systems to be developed responsibly—as long as enough open space is maintained for wildlife.

This isn’t to say that huge arrays make sense everywhere, just as wind turbines don’t belong everywhere. Having served as a trustee of the Vermont Chapter of The Nature Conservancy for nine years, I am well aware of the need for natural, undisturbed habitat.

Detail of the advanced Schüco PV panels, which can also be installed at building-integrated PV (BIPV).
Photo Credit: Alex Wilson

But I’m also aware that if we don’t address our greenhouse gas emissions, we will be doing far more damage to ecosystems than the solar arrays (and wind farms) that are coming under more widespread attack.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-12-18 n/a 18001 Flywheels: A Cleaner Way of Stabilizing Our Electricity Grid

Beacon Power pushing the envelope and creating a more resilient utility grid with large-scale flywheel power storage

Schematic of Beacon Power's Energy Smart 25 flywheel.
Photo Credit: Beacon Power

After I wrote last week about a company developing power grid electrical storage systems using lithium-ion battery technology, a reader alerted me to another, very different approach for storing electricity to make the utility grid more stable and resilient: flywheels.

We've written before about flywheel electrical storage for use in data centers to provide instantaneous back-up power that can last for a few minutes until back-up generators can be started up. But I had not been aware of utility-scale projects that were in operation.

How flywheel electricity storage works

The idea with a flywheel for power storage is that a small amount of electricity is used to keep a heavy mass rotating at a very high speed—10,000 revolutions per minute (rpm) or faster. Then when power interruptions happen or some extra power is needed to stabilize the grid, that flywheel gradually slows down, generating power in the process. It essentially stores energy in a kinetic form until needed.

People like me who read Popular Science have been hearing about the potential of flywheel energy storage for decades; for me, it has been one of those technologies that has been perpetually “just a few years away" from commercialization.

Beacon Power leading the way with flywheel storage

Flywheels arriving by truck at the construction site.
Photo Credit: Beacon Power

The energy storage company Beacon Power, located in Tyngsboro, Massachusetts (north of Boston), has been a technology leader with utility-scale flywheel power storage since its founding in 1997. In September 2013 the company put online the first 4 megawatts (MW) of a planned 20 MW flywheel energy storage facility in Hazle Township, Pennsylvania. The full system should be completed in the second quarter of 2014.

Beacon Power almost became another Solyndra story. In 2010, Beacon Power received a $43 million loan from the government, and then filed for bankruptcy in October 2011.

Beacon Power’s bankruptcy was, in part, the result of a change in federal regulations that delayed the requirement for grid operators to pay more for electricity from sources that could feed additional power into the grid very quickly—this affected Beacon Power’s cash flow. Fortunately, the private equity firm Rockland Capital stepped in and acquired Beacon Power and has now paid back most of the Department of Energy loan.

The company is back on its feet and moving full steam ahead.

Stabilizing the utility grid with flywheel storage

Schematic showing the layout of a 20 MW Beacon Power flywheel system.
Photo Credit: Beacon Power

The Pennsylvania flywheel energy storage facility can almost instantly (in less than one second) begin injecting significant amounts of electricity into the grid. This will help to stabilize the utility grid—the operation of which is a constant balancing act between supply and demand. Adding this capability—whether with a flywheel or a more conventional chemical battery—makes the grid less prone to blackouts and, thus, more resilient.

The flywheel system is modular, comprised of many of Beacon Power’s Smart Energy 25 flywheels, each of which can deliver up to 25 kilowatt-hours (kWh) of electricity. When delivering power at a capacity of 100 kW, full discharge takes about 15 minutes. When providing 150 kW (heavier power draw), full discharge occurs in 5 minutes with only 12.5 kWh delivered.

The flywheel itself, according to the Beacon Power website, has a rotating carbon-fiber composite rim, levitated on magnetic bearings so that it operates in a near-frictionless, vacuum-sealed environment. It rotates at 16,000 rpm and is designed for a 20-year life with 100,000 full-discharge cycles.

The Hazle Township 20 MW installation under construction.
Photo Credit: Forbes Magazine

According to Beacon Power, the company’s flywheel power storage system “corrects imbalances more than twice as efficiently as traditional generators while consuming no new fuel, producing no emissions, and using no hazardous materials or water.”

The power grid of the future

Beacon Power’s flywheel system is one example of a variety of new energy storage technologies that promise to make tomorrow’s electric grid quite different from what we have today. As a higher percentage of renewable energy sources, such as wind and solar, feed power into the grid, it will become more and more important to have systems like this that can store power when there is excess available and deliver that power when needed.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-12-11 n/a 17998 Solar-Powered Microgrids Could Protect Us from Power Outages

Solar Grid Storage is at the forefront of efforts to use renewable energy to create a more resilient utility grid 

The PowerFactor250 from Solar Grid Storage. Click to enlarge.
Photo Credit: Solar Grid Storage

Last week I reported on The Navy Yard in Philadelphia, a remarkable 1,200-acre business campus with 300 companies employing 10,000 people—with as many as 35,000 employees projected eventually. What had attracted me to the facility was an innovative demonstration that’s been launched showing how solar-electric (PV) systems with battery back-up and smart controls can help to create a more resilient power grid.

The emergence of microgrids

With more intense storms, wildfires, terrorist actions, and other events causing widespread power outages—and likely to cause increasingly common outages in the future, according to many experts (see Resilient Design—Smarter Building for a Turbulent Future)—there is growing demand for creating islandable “microgrids.”

Microgrids are small to moderate-size power grids, often serving university or medical campuses, that have the capability to be isolated from the regional power grid in the event of a widespread outage. Such systems must have their own generation capacity along with sophisticated electricity management systems.

Schematic of a microgrid with the Solar Grid Storage PowerFactor system. Click to enlarge.
Image Credit: Solar Grid Storage

More than fifty military bases have created, or are in the process of creating, microgrids. Military facilities have to maintain operability, even if widespread outages occur, so they are a natural for microgrids. Some universities and hospital complexes have also created microgrids, and the State of Connecticut, heavily hit by Superstorm Sandy, Tropical Storm Irene, and a freak October snowstorm in 2011, has passed legislation to create demonstration microgrids in eight cities.

Another advantage of microgrids is that the small-scale power generation needed for such systems takes place close to where the power is being used, so if there is waste heat created in the generation process (as occurs with generators that use steam turbines or fuel cells), that heat can be captured and productively used—referred to as cogeneration or combined heat and power (CHP).

How a small amount of electricity storage can boost grid resilience

Our electricity grid is a complex and hard-to-manage system. The amount of power (electricity) being generated has to be closely balanced with the amount of power being consumed (demand). Fluctuations in demand occur all the time. In the morning hours between 6–8 a.m., for example, a lot of people get up, turn on lights, shower, operate their coffee makers, and turn up the heat (or air conditioning); electricity demand rises significantly.

Schematic of the PowerFactor250 module. Click to enlarge.
Image Credit: Solar Grid Storage

One of the big challenges in managing this fluctuating demand is that most generators can’t be turned on and off quickly. You can’t just throw a switch and expect a several-hundred-megawatt generator start cranking out electricity.

With renewable energy power-generation systems—particularly wind and solar—fluctuations in output provide another complication. When the wind stops blowing the output from a wind farm ceases, and when clouds obscure the sun the output of PV systems drops dramatically.

Battery storage in a power grid allows electricity to be stored when more is being generated than consumed, and it allows electricity to be pulled out of storage when demand exceeds supply. The same battery bank can allow a critical loads in a microgrid to remain powered when the regional grid goes down. This role of batteries in managing the output from wind and solar systems is important and will grow in significance as the percentage of our electricity supplied by renewables grows.

Solar Grid Storage

Based in Philadelphia, with a few other offices spread around the Northeast, Solar Grid Storage offers a modular system for managing the output of PV arrays and storing power to better balance the output and power availability from large, grid-connected PV systems.

Advanced, lithium-ion batteries are used in this system. This technology avoids the use of heavy metals like lead and cadmium that are used in other batteries. The technology also allows deep discharge without wearing out the batteries and very rapid recharging—though the technology is more expensive than older battery technology.

The business model for Solar Grid Storage is that the owner of a large PV array would own just the actual array, and Solar Grid Storage would own the inverter, battery system, and other equipment needed to manage the system. These components come packaged in a 20-foot container, which the company (confusingly) trademarked as PowerFactor (at least it's confusing to those of us who have been trying for years to fully understand what power factor means).

The battery bank and controls allow the system to take over instantaneously in the event of a regional power outage.

One of the first four of these systems has been installed at The Navy Yard, and my colleagues and I got a chance to tour this facility. This PowerFactor250 system includes a 250 kW inverter and has 125 kWh of battery storage. Being modular, it is shipped directly to the site and can be hooked up quickly. 

Another view of the PowerFactor module.
Photo Credit: Alex Wilson

Another, larger PowerFactor system was installed in October, 2013 in Laurel, Maryland for the real estate developer Konterra. That PowerFactor500 system manages power from a 402 kW solar array that is integrated with parking lot canopies, and it includes 300 kWh of battery storage (though 250 kWh would be more typical with the 500 kW inverter). It includes critical loads power that can provide 50 kW of electricity for just over four hours—or more when the sun is shining and generating power.

Innovation just beginning

The Solar Grid Storage installations are cutting-edge examples of what we can expect in the years ahead as efforts to effectively integrate renewable energy into the utility grid move forward. “Adding storage to solar projects makes them even more valuable to customers and also provides new benefits to the grid—and all ratepayers,” Solar Grid Storage CEO Tom Leyden told me. “We are proud to be part of what we believe will help usher in the grid of the future.”

I believe that such innovations will demonstrate very effective synergies between solar energy (and other renewables), the goals of resilience, and the efficient operation of the power grid. It should be fun to watch!

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-12-03 n/a 17930 The Navy Yard at the Forefront of Philly’s Green Rebirth

Philadelphia’s Navy Yard is achieving robust economic development while demonstrating a wide variety of energy innovations

One of the restored, historic buildings at The Navy Yard that serves Urban Outfitters.
Photo Credit: Alex Wilson

I’m just back from Philadelphia, where I spent most of last week at Greenbuild, the nation’s premier conference and expo focused on the burgeoning green building movement. I heard there were 25,000 attendees….

Several of us had the opportunity to visit The Navy Yard, which I had been hearing a lot about.

New life for an old military base

The Philadelphia Naval Shipyard, which had its origin in 1776 and relocated to the present site at the confluence of the Schuylkill and Delaware Rivers in 1871, was the nation’s first naval facility. Fifty-three naval ships were built here, including the famed New Jersey and Wisconsin battleships in World War II; some 574 ships were repaired here. At its peak in the 1940s the shipyard employed 40,000 people.

The 600 kW Bloom Energy solid-oxide fuel cell installation at The Navy Yard.
Photo Credit: Alex Wilson

The shipyard was largely shut down in 1995, though some Naval operations have been retained on the site. The Navy Yard, as it is now known, was considered an eyesore to many, with derelict buildings and infrastructure sorely needing a facelift, but some saw the potential of this property. The City of Philadelphia took over the facility and, with various partners, began working to make it into a driver of economic development through the Philadelphia Industrial Development Corporation.

Today, the Navy Yard, which occupies 1,200 acres, houses more than 300 vibrant businesses that employ 10,000 workers. The facility got a major boost and critical mass in 2006 when Urban Outfitters moved its corporate headquarters into four large renovated buildings there; the company (which includes brands Anthropologie and Free People) currently employs 1,400 in 400,000 square feet of commercial space, in a strong demonstration of adaptive reuse and green rehabilitation tied to historic preservation.

The cavernous interior of the Urban Outfitters headquarters.
Photo Credit: Alex Wilson

This year, the pharmaceutical company GlaxoSmithKline relocated from Suburban Philadelphia to a newly built, 208,000 square-foot corporate headquarters building that has achieved LEED Platinum certification. Liberty Property Trust, one of the nation’s leading green-focused real estate investment trusts with 67 LEED projects either completed or underway, has been the guiding force for much of the real estate development at the Navy Yard.

Master planning at its best

Many of the most progressive development projects today are occurring on sites where large-scale master planning is possible. That has often been the case where military bases are shut down. The Navy Yard may be the most successful such project yet.

Robert A.M. Stern Architects led the master planning process in 2004, and that plan has just been revised with the 2013 Update. Sustainability is a big part of the Master Plan, and that has been driven in part by Philadelphia Mayor Michael Nutter’s goal to make Philadelphia the nation’s greenest large city. It’s an impressive plan and well-presented in an online document.

Among the features in the master plan are the following:

  • Mixed-use inner-city development (with 6.2 million square feet of office and research space, 5.7 million square feet of industrial space, and 1,018 housing units planned in the Historic District)
  • Continued job creation with 36,000 jobs projected for the Navy Yard at buildout
  • Continued emphasis on green building—nine of eleven new buildings at the Navy Yard are LEED-certified
  • An extensive network of pedestrian walkways, bicycle lanes, and bicycle paths throughout The Navy Yard
  • Public transit links to the nearby Philadelphia International Airport and downtown, including expanded bus routes and feasibility studies underway for a subway extension to the Navy Yard, with two stations
  • An extensive collection of stormwater features to manage water onsite and minimize pollution entry into the Delaware River
  • Extensive open space, community gathering areas, and buffer zones, with public linkages between neighborhoods (though turf area has to be coordinated with the Federal Aviation Agency to discourage geese—which pose a threat to aviation at Philadelphia Airport)
The GridSTAR house with various solar installations.
Photo Credit: Alex Wilson

Smart Grid and other energy innovations

Because the Navy Yard is being redeveloped through a central master plan, there are some exciting opportunities that have been realized, including the creation of a microgrid. Microgrids, which are small utility grids that can be separated from the regional power grid when necessary to prevent blackouts, offer important resilience benefits.

There are some exciting power-generation systems being used. After wandering through the cavernous Urban Outfitters corporate headquarters, the three of us from BuildingGreen spent a while trying to find the innovative fuel cell system that powers 60% of the Urban Outfitters’ operations and has reduced its carbon emissions by 52%.

This Bloom Energy solid-oxide fuel cell system uses natural gas to produce electricity, but rather than burning the electricity, as most power plants do, fuel cells operate chemically to produce electricity and waste heat that can be captured. Fuel cells are like batteries that keep operating as long as hydrogen fuel (from natural gas) is provided.

A car-charging station at the GridSTAR net-zero-energy demonstration house at The Navy Yard.
Photo Credit: Alex Wilson

The Navy Yard is housing several other leading-edge energy research programs. The Energy Efficient Buildings Hub (EEB Hub), created by the U.S. Department of Energy and managed by Penn State University, is based at the Navy Yard and has a dual mission of advancing energy conservation in the commercial building sector while spurring economic growth.

The EEB Hub has just completed the GridSTAR zero-net-energy demonstration home at the Navy Yard that we toured. They are also creating the Smart Energy Campus and the Center for Distributed Energy, both of which are based there. Innovative research is being conducted on the use of plug-in electric and electric-hybrid vehicles as a way to provide distributed energy storage for the power grid, utility-scale battery storage to enhance grid reliability, and various renewable energy systems, including a new solar shingle I hadn’t seen.

Final thoughts

The Navy Yard demonstrates the benefits of coordinated master planning. While such comprehensive opportunities don’t exist everywhere, elements of such planning, including smart-grid technology and microgrids, can be incorporated widely. It was exciting to see everything going on the Navy Yard, and I look forward to going back and having more time to explore.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-11-26 n/a 17921 Producing Ethanol From Corn Is a Bad Idea

Producing ethanol from corn is a bad idea not only because of the poor energy return on investment (EROI), but also because of the impact it is having on ecosystems in the Midwest

Production of ethanol has dramatically increased acreage devoted to corn in the Midwest.
Photo Credit: Lynn Betts, USDA-NRCS

Corn-based ethanol as a vehicle fuel has never been a good idea. But an in-depth investigation by Dina Cappiello and Matt Apuzzo of The Associated Press, published last week, outlines a lot of other reasons why we should finally kill this particular farm subsidy.

Where did we get this idea to begin with? The U.S. is one of the most agriculturally rich nations in the world, and we’re also one of the world’s largest fossil fuel importers. It makes sense on some levels to convert some motor fuel to biobased sources, such as ethanol and biodiesel—because we can produce it ourselves, helping to wean our dependence on oil from the Middle East and other politically unstable or unfriendly places.

Also, in theory, biofuels should help to reduce greenhouse gas emissions, since the raw materials (corn in the case of ethanol) is produced, in part, using solar energy via photosynthesis. The Obama Administration, like the Bush Administration before it, has touted ethanol as a strategy for reducing our nation’s greenhouse gas emissions.

Energy return on investment

I’ve written here in the past about the energy return on investment (EROI) with ethanol. Depending on whose study you believe it either takes a little more or a little less energy to produce corn-based ethanol than that end-product contains. That EROI ratio ranges from 0.8:1 to 1.5:1, depending on the study.

Any time the EROI is less than 1:1, it takes more energy to produce the fuel than the fuel contains. Even giving the ethanol industry the benefit of the doubt by assuming the actual EROI is 1.5:1, that means to produce a gallon of the fuel takes two-thirds of a gallon (equivalent) of fuel—diesel for tractors and combines on the farm, natural gas to produce nitrogen fertilizer, natural gas and electricity at the ethanol plant, and energy to ship that fuel around the country.

By comparison, the ethanol produced from sugar cane in Brazil has an EROI closer to 8:1—for every gallon (equivalent) invested you get about eight gallons back out.

No matter whose numbers you believe, from an energy standpoint turning corn into ethanol to fuel our cars makes little sense.

Corn production is energy-intensive and results in significant nutrient pollution.
Photo Credit: USDA-NRCS

Land conversion to corn production

Even more troubling than the dubious energy balance of ethanol is the land conversions that have occurred as demand for corn has increased in recent years. Just since 2008, according to the AP investigation, more than 5 million acres of land that had been set aside as part of the Conservation Reserve Program have been converted to corn production—an area greater than Yellowstone, Yosemite, and The Everglades National Parks combined.

Since 2006, some 1.2 million acres in Nebraska and the Dakotas that had never been tilled have been converted to corn and soybean production. This is even worse than converting conservation acreage into tilled farmland—since much of the conservation land had once been tilled. When virgin prairie is converted to farmland, along with losing the biodiversity on that land, a significant amount of carbon that was stored as organic matter in the soil is released into the atmosphere—contributing to greenhouse gas emissions.

Increased fertilizer use

The dramatic increase in corn production in recent years has also dramatically increased fertilizer use. Between 2005 and 2010, according to the AP investigation, nitrogen fertilizer use increased by 1 billion pounds, with another billion-pound increase likely having occurred since 2010.

Along with requiring a lot of natural gas to produce all that fertilizer, the runoff from that farmland is a huge pollution problem and contributes directly to the “dead zone” that occurs each year in the Gulf of Mexico.

If you've read our report on biobased materials in building products (see Biobased Materials: Not Always Greener), none of this should come as a great surprise. Behind seemingly good environmental ideas often lie complexities and negative impacts.

Corn for energy vs. food

As demand for corn increased to meet increasing mandates for ethanol in U.S. gasoline, the price of corn increased (commodity pricing is driven by supply and demand). In our increasingly global markets this affected food prices in developing countries that rely heavily on corn. Corn prices climbed to $7 per bushel in the U.S., double what they had been a few years earlier, and this dramatically increased food prices in Mexico, leading in some places to food riots.

Prices of corn have since dropped somewhat and record harvests are expected this year, but prices are still above where they were ten years ago.

Reevaluating our ethanol policy

The AP report came out just as the Obama Administration is reconsidering the ethanol mandates that have fueled the dramatic increase in corn production. The U.S. Environmental Protection Agency has proposed scaling back on the biofuel mandates in the Renewable Fuel Standard. Legislation passed in 2007 called for increasing the production of biofuels each year, with production reaching 16.55 billion gallons this year (2013) and rising to 36 billion gallons by 2022.

Corn harvest in Iowa.
Photo Credit: Tim McCabe, USDA-NRCS

But when that legislation was passed, the consumption of gasoline was expected to continue rising, so the quota could have been achieved without increasing the percentage of ethanol in gasoline beyond the 10% that car makers are comfortable with. More ethanol in gasoline can cause corrosion in engines. With cars and light trucks becoming more fuel efficient, the numbers weren’t working.

EPA has proposed scaling back the ethanol mandate in 2014 to 15.21 billion gallons, down 14% from where it would be under the Renewable Fuel Standard—and just under 10% of the motor fuel sold in the country. An unusual coalition of oil companies and environmentalists is proposing going further and eliminating the biofuel mandates altogether.

The road ahead

I, like many others, have been hoping that “cellulostic ethanol” (made from agricultural residue like corn stalks rather than high-value corn) would advance more quickly than it has. So, along with proposing a reduction in the overall biofuel mandate, EPA last week proposed cutting the target for so-called “advanced biofuels” from 2.75 billion gallons this year to 2.2 billion gallons next year.

In the coming weeks, during the 50-day comment period for the new EPA rules, expect to see a barrage of dueling television ads on this issue.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-11-18 n/a 17919 Is There a Place for Vacuum Insulation in our Buildings?

For insulating our buildings, vacuum insulation panels may not be cost-effective, but they will become common in other applications

Microtherm's vacuum insulation panel, with a microporous substrate covered with an impermeable aluminum skin. Click to enlarge.
Photo Credit: Microtherm

I’ve recently worked on revising the BuildingGreen Guide to Insulation Products and Practices (available as part of a webcast), so I’ve been steeped in all sort of insulation materials, including some oddball products. One of those is vacuum insulation—operating on the same principle as a Thermos bottle.

Vacuum insulation is a great idea—in theory. To understand why, it helps to know a bit about heat flow.

How a vacuum slows down heat transfer

There are three modes of heat transfer: conduction, convection, and radiation, and if we remove most of the air molecules from a space—as occurs when we draw a vacuum—we largely eliminate the first two of those heat transfer mechanisms.

Conduction is the flow of heat from molecule to molecule. It’s the reason a cast iron skillet handle heats up, but thermal conduction also occurs across a layer of air, as kinetic is transferred from one air molecule to the one next to it. If we remove most of those air molecules by creating a vacuum, there will far less conductive heat flow.

Convection is the transfer of heat by moving molecules from one place to another. Warm air rises, and these convection currents carry heat—for example, this is the primary means that heat is delivered to a room from baseboard convectors (often called radiators). In a vacuum there are far fewer air molecules so convection of heat nearly stops.

A sampling of vacuum insulation panels from Nanopore.
Photo Credit: Nanopore

Only radiant heat flow occurs to a significant extent in a vacuum, because radiation is not dependent on air molecules. That’s why low-emissivity surfaces are so important in vacuum panels. The Stanley Thermos bottle has a very shiny, low-emissivity (low-e), inner surface that helps to reduce radiant heat transfer; the same sort of low-e surface is included in various vacuum insulation panels.

The net result is that an inch-thick vacuum insulation panel can provide a center-of-panel insulating value of R-25 or even more—compared with R-6 to R-7 for standard rigid foam insulation.

The “hardness” of a vacuum

The key property of a vacuum is it’s pressure or how “hard” it is. We often measure that with Torr units. One Torr is exactly 1/760th of a standard atmosphere (1.3 x 10-3 atm), or approximately 1 mm of mercury. With a very hard vacuum, more of the air molecules are sucked out, resulting a greater negative pressure. The walls of a typical Stanley Thermos bottle contain a relatively hard vacuum of 10-6 Torr. With such a hard vacuum, that Thermos bottle can keep coffee hot all day. By comparison, the vacuum in a flat vacuum insulation panel is typically no more than 1/1000th as strong (10-3 Torr).

The harder the vacuum, the more difficult it is to maintain it. Thermos bottles are made with a cylindrical design for optimal strength. With flat panels, it’s very hard to achieve comparable strength and maintain such a hard vacuum—particularly at the edges.

Using vacuums to insulate more than our coffee

If vacuums work so well to keep our coffee hot all day, why not use them to insulate our houses? Vacuum insulation panels have been used to insulate some high-tech demonstration homes, such as entrants in the Solar Decathlon student design competition in recent years, but high cost makes them impractical for real buildings.

There’s also the problem that puncturing that vacuum insulation panel will significantly reduce it’s insulating performance. (I can imagine how bummed one would be after spending thousands to insulate a home with vacuum insulation panels and then hearing a hiss while hanging a painting!)

However, these vacuum insulation panels (sometimes called VIPs) could make a great deal of sense in certain value-added products like refrigerators, freezers, water heaters, and entry doors. Whirlpool actually used a VIP that Owens Corning produced for a while (the Aura panel) in a high-efficiency refrigerator in the mid-1990s, but then dropped both the refrigerator and the use of VIPs.

But I believe the benefits of R-25 or more in a one-inch-thick panel are significant enough—especially as we try to get more usable volume in refrigerators without growing the exterior dimensions—to warrant the embrace of vacuum insulation. These could also be a great solution for exterior doors that are notoriously poorly insulated—as I’ve written about in this blog.

There are at least a half-dozen manufacturers of vacuum insulation panels today. Most, including Microtherm and Nanopore, produce panels that have a rigid, porous substrate surrounded by an impermeable metal skin.

Dow Corning's new vacuum insulation panel is encased in mineral wool to protect it. The company looks to incorporate this product into commercial building facades.
Photo Credit: Dow Corning

A new VIP on the market

The latest VIP  to come along is made by Dow Corning (no relation to Owens Corning). This panel, not yet widely available, is one inch thick and has a center-of-panel insulating value of R-39 and a “unit R-value” (accounting for the edges) of R-30, according to the company.

The Dow Corning product has a core made of fumed silica cake, a remarkable “microporous” material that provides R-8 per inch even without a vacuum. This material allows a very high insulating value even with a softer vacuum. The core is reinforced with silicon carbide and polyester fibers for structural support, and it is encased in an inner layer of polyethylene and an outer layer of polyethylene, polyester, and aluminum. The panels are vacuum-sealed, and the edges are heat-sealed.

According to an Environmental Building News article, these Dow Corning panels should cost $10-12 per square foot. At that cost, I believe VIPs can be very practical for those appliance and exterior door applications noted above.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-11-13 n/a 17895 Mineral Wool Insulation Entering the Mainstream

Owens Corning’s entry into the mineral wool insulation market with the purchase of Thermafiber, promises a higher profile for this insulation material

Thermafiber's new UltraBatt mineral wool insulation is distributed nationally through Menards. Click to enlarge.
Photo Credit: Thermafiber

I recently reported that a new mineral wool insulation product from Roxul can be readily used in place of foam-plastic insulation materials like polystyrene in certain applications. As part of our ongoing research into how builders and designers can make better insulation choices (see our full webcast and report on the topic), I have new mineral wool developments to report.

First, a little background: mineral wool, variously referred to as rockwool, slagwool, and stone wool, was one of the first insulation materials to be widely produced commercially—starting back in 1871 in Germany.

Rockwool International, the world’s largest producer of mineral wool and the parent company of Canadian manufacturer Roxul, began production of the material in 1937. The U.S. company Thermafiber, one of the largest U.S. producers of the material and a company poised for rapid growth today, was founded in 1934.

Mineral wool is made by melting the raw material, which can be stone (such as basalt) or iron ore slag, at very high temperature, spinning it like cotton candy to produce very thin fibers, coating those fibers with a binder to hold them together, and forming it into the insulation batt or boardstock material to meet specific product needs.

Mineral wool lost most of its market share when less-expensive fiberglass insulation came along, but unique properties of the material have been fueling a comeback in recent years—and this year the world’s largest fiberglass insulation company, Owens Corning, purchased Thermafiber. With this development, I’m expecting to see a lot of attention paid to mineral wool in the coming years—led by a new product introduction last week.

Mineral wool's pluses

Mineral wool is highly fire resistant, which has long made it an insulation material of choice in many commercial buildings. It achieves its fire resistance without the use of any flame retardant chemicals, which are widely used in most foam-plastic insulation materials—and which I believe to be a huge downside of those products.

Mineral wool is a heavier and more dense insulation material that fiberglass, giving it better sound-control properties and more effectively restricting air movement through it. When produced in boardstock form, mineral wool can be rigid enough to work as insulative sheathing, like extruded polystyrene and polyisocyanurate.

Mineral wool can also contain very high recycled content by using iron ore slag (a waste product from steel manufacturing). Some mineral wool products on the market have over 90% recycled content—higher even than cellulose insulation, though it is made from pre-consumer rather than post-consumer recycled material.

The downside to mineral wool

There are three major downsides to mineral wool. One is that mineral fibers can break off and become airborne; when we breathe those fibers in they can cause health problems. In the past there was some concern that mineral wool and fiberglass fibers might be carcinogenic, like asbestos. While those concerns have largely been dismissed, the fibers are still respiratory irritants. Installers of mineral wool should always wear quality dust masks, and the material should be adequately covered with drywall or coatings that prevent fibers from entering the indoor air in a building.

The second downside is the binder used to glue the fibers together. Manufacturers use a phenol formaldehyde or a urea-extended phenol formaldehyde binder. Formaldehyde is a known human carcinogen, and if a lot of it escapes into the indoor air, that would clearly be a health concern. Fortunately, the processing drives off nearly all of the free formaldehyde in the material, so formaldehyde emissions from mineral wool have extremely low formaldehyde levels—in some cases as low as background formaldehyde levels.

Nonetheless, there is a perception problem with formaldehyde binders—if not a real problem—and manufacturers are working on alternatives—as has occurred with fiberglass insulation. I fully expect that within a few years one of the mineral wool manufacturers will announce a biobased binder that works with mineral wool and the industry will fairly quickly convert to such a binder.

The third downside to mineral wool is that it can be hard to work with. Mineral wool boardstock is more compressible than rigid foam-plastic insulation, so installing strapping over it may take special care. In the batt form, the insulation doesn’t compress as easily as fiberglass to squeeze into odd corners and around wires. That can make mineral wool harder to work with—but it should also prevent some of the worst installation problems that occur with fiberglass. (The effectiveness of all types of batt insulation depends to a very significant extent on the care taken during installation.)

UltraBatt is an unfaced mineral wool insulation that offers very good fire resistance and sound control.
Photo Credit: Thermafiber

Thermafiber’s new mineral wool batt insulation

The latest news with mineral wool is the introduction by Thermafiber (now an Owens Corning company) of UltraBatt, a flexible batt insulation product for 2x4 or 2x6 walls. This follows Roxul’s introduction of a widely distributed mineral wool batt insulation product, ComfortBatt, several years ago.

UltraBatt is a fairly dense batt (not compressible like fiberglass batts) that offers very good sound control as well as relatively high insulating values. The 3-1/2” batts for 2x4 walls provide R-15, and the 5-1/2” batts for 2x6 walls provide R-23—though, as with all cavity-fill insulation, that actual “whole-wall” R-value will be lower, due to thermal bridging through the studs.

UltraBatt is comprised of 70% post-industrial recycled content. As for pricing, the national distributor Menards showed the online price to be about $31 per 40 square feet in the 3-1/2” batts, or about $0.77 per square foot. This compares with unfaced CertainTeed fiberglass batts at about $23 for 88 square feet, or $0.26 per square foot. The installed cost of dense-pack cellulose, meanwhile, is typically $1-2 per square foot for a 2x4 wall, though the pricing of any contractor-installed insulation is very dependent on the project.

I have not seen test data on formaldehyde (or other) emissions from UltraBatt, but I was told by Owens Corning that testing is underway and findings will be reported in 2014. I suspect that, like Roxul’s ComfortBatt, the formaldehyde emissions will be very low.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-11-06 n/a 17827 Insulation Quiz: The No-Foam Challenge

How well do you know your insulation? Photo: BuildingGreen, Inc.A lot of people are questioning the widespread use of foam insulation. Are you familiar with their concerns, and the upsides and downsides of alternatives?

What are all the environmental and health challenges presented by foam insulation products? What about the healthier substitutes? Are they ready for prime time?

These are some of the questions tackled by our new report, and accompanying webcast and course, Choosing and Detailing Insulation for High-Performance Assemblies. Even as more designers and builders are thinking twice about using rigid and spray-applied foam insulation, the alternatives to these products are sometimes misunderstood.

Our pop quiz tests your knowledge of the application-specific challenges and opportunities of these materials. Score yourself, and then read our answers and explanations below.

1) Toxic flame retardants, high global warming potential, and high embodied energy are all environmental reasons we are concerned about rigid foam insulation products. But it has a lot going for it in terms of performance: high R-value per inch, high compressive strength, and it’s easy to install. Which of the following is a performance-based reason you might think twice about using rigid foam?

A) It’s susceptible to ant and termite nesting and tunneling, even if completely dry
B) At best, it’s only semi-vapor permeable, and can trap moisture
C) Foam is relatively flammable, even with flame retardants added
D) All of the above

2) Rigid mineral wool has become a top pick for designers and builders looking to avoid foam insulation. They have had to make some changes, though, and overcome obstacles to do that. Which of the following is NOT a downside to using rigid mineral wool?

A) It’s not quite as “rigid” as rigid foam insulation.
B) Particularly in versions with higher compressive strength, its R-value is lower than foam insulation, and boards are heavier.
C) It’s not cost-competitive to purchase
D) It’s harder to cut than foam.

3) Which of the following insulation products are air barrier materials?

A) Extruded polystyrene insulation (XPS)
B) Polyisocyanurate
C) Closed-cell spray-polyurethane foam
D) Cellular glas, i.e. Foamglas
E) Cellulose
F) Cellular foam, i.e. Airkrete
G) Rigid mineral wool
H) Spray-applied fiberglass
I) Expanded polystyrene insulation (EPS)
J) Open-cell spray-polyurethane foam
K) Radiant barrier sheets

4) You want to avoid use of foam insulation in a wall assembly, but a tight air barrier is important to you. Which of the following are valid options?

A) you're stuck with foam—any high-performing building today uses some foam as an air barrier
B) use sheathing that acts as an air barrier and tape the seams
C) use concrete-masonry units (CMUs), or cast-in-place concrete
D) use high-performance caulks or gaskets at key junctions such as at floorplates and penetrations
E) B and/or D
F) B and/or C and/or D

5) Expanded cork insulation is _______, but is _______.

A) made of recycled wine corks; very low in R-value
B) 100% cork including the binder; labor-intensive to install
C) 100% cork except for the binder; high in VOC emissions
D) made in the U.S.; relatively expensive 

6) Cellular glass, i.e. Foamglas, is _______, but is _______.

A) made in the U.S.; relatively expensive
B) completely impervious to moisture and insects; not very high in compressive strength
C) completely inert when cut or scored; extremely heavy
D) usable at very high temperatures; very low in R-value per inch

7) Rigid mineral wool insulation is _______, but is _______.

A) made with recycled content; much more expensive than foam
B) higher in R-value than foam; not always stocked at regional lumber yards
C) low in embodied energy; new to many contracting crews
D) flame-resistant without flame retardants; not as rigid as rigid foam 

8) Spray-polyurethane foam is _______, but is _______.

A) sometimes made of high percentages of soy oil; still partly synthetic
B) an air barrier; laced with chlorinated flame retardants
C) one of the best available choices for insulating uneven surfaces; often applied with high global-warming-potential blowing agents
D) relatively inexpensive; reported to be linked with building fires and unusual odors in faulty installations

9) Avoiding toxic chemicals and allergens is particularly important to you in your choice of insulation. If you’re extremely thorough in avoiding toxic chemicals, which insulation is the best choice?

A) cellulose
B) cellular glass
C) cementitious foam
D) low-density wood-fiber insulation
E) wool
F) spray-in-place fiberglass

10) The ability of a building envelope to dry out in both directions if it gets wet is important to your project. Which insulation material might you take special interest in using?

A) foil-faced polyisocyanurate
B) rigid perlite board
C) low-density wood fiber insulation
D) extruded polystyrene (XPS)
E) high-density spray polyurethane foam

Our answers—and why

Question 1—D, all of the above. Extruded polystyrene in particular is known in the carpenter ant community as a favorable texture to nest in, even in the absence of moisture, and even though they don't technically consume it as food. Most foam insulation products are Class II vapor retarders. And even with the addition of toxic flame retardants, some foam insulation can ignite and contribute to a fire relatively quickly.

Question 2—C) It’s not cost-competitive to purchase. Mineral wool may require a special order through your supplier, but it is often less expensive than XPS— something we were surprised to learn in our research, and that may indicate a trend as mineral wool becomes more popular and domestic production increases.

Question 3—A through D are air barrier barrier materials, E through I are not, and with J and K, it depends. Air barrier performance, R-value, vapor permeability, and other key environmental performance data for these and other insulation materials is in our report. Why do we say "it depends" for open-cell spray foam and radiant barrier sheets? With the latter, the material itself is usually an air barrier, but it's not meant for that purpose. Fastening without penetrations and extensive taping or other seam-sealing would be required. With open-cell foam, it simply varies by the type of product.

Question 4—E) B and/or D. This is a bit of a trick question, because C would qualify on the merit of cast-in-place concrete, but CMUs are porous to air except when accompanied by mastic or sealant.

Question 5—B) 100% cork including the binder; labor-intensive to install. Expanded cork is processed under heat and pressure that activates a natural binder. It is relatively difficult to cut and install, as regular readers of our blogs may recall.

Question 6—A) made in the U.S.; relatively expensive. With some of the more exotic foam alternatives being imported from Europe, it may be surprising to learn that Foamglas has been made in the U.S. (at two different factories) for decades. For the record, its R-value per inch is respectable, it is completely impervious to moisture and insects, but it does emit a touch of hydrogen sulfide gas when scratched.

Question 7—D) flame-resistant without flame retardants; not as rigid as rigid foam. The answer to this question highlights a key benefit of mineral wool insulation, but also a downside, that it is not quite as rigid as foam, which some builders whine about when it comes to installing cladding over it. They should get over it, and just add plenty of continuous exterior insulation, which requires furring no matter whether it's foam or mineral wool.

Question 8—C) one of the best available choices for insulating uneven surfaces; often applied with high-global-warming-potential blowing agents. We have to admit that when it comes to insulating uneven surfaces, such as a retrofit of a masonry wall, spray-polyurethane foam (SPF) is hard to beat. But keep in mind the climate impact. And for the record, soy is typically only a token ingredient, and SPF has been linked—though some would say demonized—in fires and incidents of odors and chemical sensitivity.

Question 9—C) cementitious foam. Better known as Airkrete, the only product we're aware of that is sold under this description, cementitious foam is the most inert, nontoxic insulation product we are aware of. Each of the other products—even cellulose and its borates and wool with its allergenic properties—has a chemical ingredient or process, about which there is some concern.

Question 10—C) low-density wood fiber insulation. Best-known in the U.S. as the imported Agepan, low-density wood fiber insulation is becoming popular in advanced building systems, such as Passive House projects, in part because of its high vapor permeability, which enables good drying potential—especially important for airtight assemblies.

Your answers and comments

Our quiz was meant to be a little "tricky" and it is even rumored that the author had the BuildingGreen special report, Insulation Choices: What You Need to Know About Performance, Cost, Health and Environmental Considerations, in hand and referred to it frequently while writing the questions (he also says it's not only useful but very affordable, especially when coupled with the insulation details and video discussion included in the accompanying four-part course).
How did you do? Comments, questions, quibbles? Post them below.
2013-10-31 n/a 17823 Formaldehyde-Based Foam Insulation Back from the Dead

Urea formaldehyde foam insulation (UFFI) has been out of the spotlight, but going into a lot of buildings—often being referred to as Amino Foam.

Amino Foam is a highly flowable foam that can fill CMU cavities from below—rising as much as 18 vertical feet. Click to enlarge.
Photo Credit: cfiFOAM

In working on major updates and expansions to Insulation Choices: What You Need to Know About Performance, Cost, Health and Environmental Considerations, we’ve had an opportunity to dig into some of the insulation products out there that you don't hear so much about. Some of what we’re found has been surprising.

Anyone remember urea formaldehyde foam insulation (UFFI)? Back in the late 1970s and early 1980s it was the ultimate bad guy of the insulation world. Installed in hundreds of thousands of homes in the U.S. and Canada following the 1973 Energy Crisis, UFFI was found to emit high levels of formaldehyde in some circumstances and shrink considerably, resulting in performance problems.

The Canadian government spent millions of dollars insulating 80,000 to 100,000 homes with this insulation, then spent many more millions uninstalling it when reports of problems emerged. Canada banned the product, as did the Consumer Products Safety Commission in 1982 in the U.S.—though the latter later reversed the ban a year later.

The industry largely disappeared. While there had been 39 manufacturers of UFFI in 1977 and upwards of 1,500 installers, that dropped to just a handful by the early-eighties. Most of us pretty much forgot about the product.

UFFI is still around

The UFFI industry shrank to just seven manufacturers by 1981, then two large producers, Borden and Ciba-Geigy, ceased production. But the remaining five companies have continued to produce UFFI, though under different names. Most of those companies have gone to significant effort to avoid any association with UFFI.

Among the five manufacturers of UFFI today, you will variously see the material referred to as “injection foam,” “amino foam,” “aminoplast foam,” “tri-polymer foam,” “dry-resin foam,” and various combinations thereof. The only reference you’re unlikely to see is “urea-formaldehyde,” and if you ask manufacturers what the stuff is most will go to great lengths to obfuscate their response.

Used for insulating concrete-block construction

The primary application for UFFI today is to insulate hollow concrete masonry units (CMUs) or concrete blocks—and I think it is a fairly good solution for such buildings. It can be also used as a retrofit insulation for wood-frame cavity walls, but there are better products for wood-frame construction.

What is it?

To really understand what UFFI is, one may need a degree in polymer chemistry. cfiFOAM, which is the most forthcoming of the manufacturers in production today, describes the material as being “part of the family of amine/furan resins consisting of phenol, urea and melamine, coupled with an aldehyde.” The company explains in a fact sheet that “amino resins are thermosetting materials produced by reacting amine groups (NH3) with an aldehyde, such as formaldehyde.”

The reaction results in a blend of three different polymers, monomethylol, dimethylol, and trimethylol-substituted urea, which leads one manufacturer, C.P. Chemical, to refer to its insulation as TriPolymer Foam. This resin is further reacted with an acid catalyst in a condensation process, and the resultant resin is dried (sometimes in a kiln) to produce a powdered, dry resin that can be stored and easily shipped.

Insulation contractors use specialized equipment to mix the powdered resin with water, surfactant, and catalyst to create the injectable foam. By carefully controlling the mix of these different components, the release of free formaldehyde—one of the main problems in the past—is greatly reduced.

Phosphoric acid is often used in this process, and that chemical imparts some fairly good fire retardant properties. To the best of my knowledge, there are no halogenated flame retardants used in any of the amino foams—which is a significant benefit of the material.

Consistency of shaving cream

Amino foams are fully expanded at the time of installation—unlike polyurethane foams, which expand as they are sprayed into a cavity or onto a surface.

The foams are very flowable, and, according to Bob Sullivan of cfiFOAM, can fill vertically as much as 18 feet, though he cautions that rapid setting can be problematic with rises above 12 feet. The flowability allows the insulation to fill concrete cores very effectively, including around hardened mortar protruding into the cores.

Misleading information on performance

Along with confusing information about what the amino foams are—and their history as UFFI—some manufacturers have grossly misleading claims about performance. The material insulates to about R-4.6 per inch, which is quite good. You may see claims of performance as high as R-5.1 per inch, but if you read the fine print, you’ll find that the higher performance claim assumes measurement at 25°F instead of the more standard 75°F.

More significantly, you may see exaggerated claims about the resulting R-value of CMU walls insulated with amino foam. Tailored Chemical Products, the manufacturer of Core-Fill 500, continues to claim exaggerated R-values above R-14 for 8-inch CMU walls insulated with the company’s UFFI insulation.

In reality, the R-value of an 8-inch CMU wall insulated with amino foam is highly dependent of the density of the concrete. With very low-density blocks—85 pounds per cubic foot (pcf)—two-core, blocks insulated with this insulation provide a whole-wall R-value of 11.3. With heavier (more dense) concrete blocks the R-values drop. With medium-density blocks (105 pcf) the whole-wall insulating value drops to R-8.2, and with high-density block (125 pcf), the whole-wall R-value drops to R-6.0. The dramatic difference between the R-value of the foam insulation alone and insulated concrete blocks results from thermal bridging through the concrete webs in the blocks.

Formaldehyde offgassing

The major problem that led to the near destruction of the UFFI industry was the fact that the material can offgas formaldehyde. Back in 1982, when the Consumer Products Safety Commission temporarily banned the material, formaldehyde was considered a “probable human carcinogen,” but the hazard warning has been upgraded to “known carcinogen.”

Formaldehyde offgassing continues to be a concern with amino foams, but improvements in the chemistry by all of the manufacturers has significantly reduced offgassing. Amino foam insulation cannot be used in a buildings going through Living Building Challenge certification (because formaldehyde is a “red list” chemical that is banned in such buildings), but for a typical CMU building, the formaldehyde issue is not nearly as significant as it once was.

Shrinkage of foam

More significant than formaldehyde offgassing, I believe, is shrinkage that can occur with amino foams. Typical shrinkage after installation is 0.5%, but in some cases shrinkage can be as much as 2%, or even 4% according to some sources. According to cfiFOAM, the impact of shrinkage is accounted for in the reported whole-wall R-values by at least that company, but it’s still a big concern.

Bottom line

UFFI (a.k.a. injection-installed amino foam) has some quite attractive features, and I believe these to be a fairly good option for concrete masonry construction. Very significantly, it is the only foam-plastic insulation that does not contain halogenated flame retardants. Were it not for the shrinkage and the lack of clear information and transparency by most of the amino foam industry, I would feel even better about it.

To see our complete listing of UFFI manufacturers, along with similar evaluations of dozens of other insulation types, see Insulation Choices: What You Need to Know About Performance, Cost, Health and Environmental Considerations.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-10-30 n/a 17812 Electric Heat Comes of Age: Installing Our Mini-Split Heat Pump

Installing a Mitsubishi air-source heat pump in our new house

The indoor unit of our Mitsubishi minisplit heat pump. Click to enlarge.
Photo Credit: Alex Wilson

Thirty-five years ago, when I first got involved with energy efficiency and renewable energy, the mere suggestion that one might heat with electricity would be scoffed at by those of us seeking alternatives to fossil fuels.

Amory Lovins, founder of the Rocky Mountain Institute, likened using electricity for heating to “cutting butter with a chainsaw.” Electricity is a high-grade form of energy; it doesn’t make sense to use it for a low-grade need like heating, he argued. It made much more sense, we all agreed, to produce that 75-degree warmth with solar collectors or passive-solar design.

So, it represents a bit shift that I’m now arguing that electricity can be the smartest way to heat a house. And that’s what we’re doing in the farmhouse we’re rebuilding in southern Vermont. I should note, here, that all of our electricity is being supplied by a solar array on our barn.

Heat pumps

Technicians from ARC Mechanical installing the outdoor unit.
Photo Credit: Alex Wilson

Heating with electricity makes sense if instead of using that electricity directly to produce heat—through electric-resistance strip heaters—we use a device called a heat pump. For every one unit of energy consumed (as electricity), two to three units of energy (as heat) are delivered. This makes heat pumps significantly less expensive to operate than oil or propane heating systems in terms of dollars per delivered unit of heat.

Heat pumps use electricity in a seemingly magic way, to move heat from one place to another and upgrade the temperature of that heat in the process. Heat pumps seem like magic because they can extract heat from a place that’s cold—like Vermont’s outdoor air in January, or underground—and deliver it to a place that’s a lot warmer.

Very significantly, heat pumps can be switched from heating mode to cooling mode with a flip of a switch. In the cooling mode, they work just like standard air conditioners.

Ground-source heat pumps (often mistakenly referred to as geothermal heat pumps) rely on the ground (or groundwater) as the heat source in the heating mode (and heat sink for cooling), while air-source heat pumps use the outside air as the heat source and heat sink. Because temperatures underground are much warmer than the outside air in winter, the efficiency of ground-source heat pumps is typically higher than that of air-source heat pumps.

But the ground-source heat pumps are really expensive. Friends in southern Vermont have spent $35,000—or even more—to install residential-sized ground-source heat pumps. The cost is so high because of trenching or drilling wells.

The outdoor unit is secured to granite blocks.
Photo Credit: Alex Wilson

By contrast, air-source heat pumps are much simpler and far less expensive. The most common types today—and what we installed at Leonard Farm—are referred to as ductless minisplit heat pumps (see Ductless Mini-Splits and Their Kin: The Revolution in Variable-Refrigerant-Flow Air Conditioning). There is an outdoor compressor (a box about three feet on a side and a foot deep), an indoor unit (evaporator with blower) that mounts on an interior wall, and copper tubing that carries refrigerant between the two.

The typical installed cost of a ductless minisplit is $3,000 to $5,000, though many variables affect the cost.

These air-source heat pumps are viable today, even in cold climates, because of dramatic improvements in the past few decades. Much of this innovation has been driven by Japanese companies, including Mitsubishi, Daikin, Fujitsu, and Sanyo (now part of Panasonic). Several decades ago, air-source heat pumps only made sense in climates that rarely dropped below 30°F in the winter; today some of these systems, including ours, will function well at temperatures below zero degrees F.

Point-source heating and cooling

Ductless minisplit heat pumps are ideally suited for compact, highly energy efficient homes. Our house has R-values greater than R-40 in the walls and R-50 in the roof, plus very tight construction with a heat-recovery ventilator for fresh air. In tight, superinsulated homes, a single space heater (point-source heating system) can work very well, because with all the insulation fairly uniform temperatures are maintained throughout the house.

Completed installation.
Photo Credit: Alex Wilson

With our 1,700 square-foot house, the two upstairs bedrooms may stay a little cooler than the downstairs, but we like a cooler bedroom. In a larger house or one that isn’t as well insulated, several ductless minisplit heat pumps or a ducted heat pump option might be required.

Our Mitsubishi heat pump

We installed a state-of-the-art Mitsubishi M-Series FE18NA heat pump that is rated at 21,600 Btu/hour for heating and 18,000 Btu/hour (1-1/2 tons) for cooling. Marc Rosenbaum, P.E. ran heat load calculations showing peak heating demand (assuming –5°F outside temperature) about 23,000 Btu/hour, assuming the air leakage we measured several months ago, before the house envelope was completed. If the air leakage ends up being cut in half from that measured level, the design heat load would drop to a little over 19,000 Btu/hour.

We think the FE18NA model will work fine for nearly all conditions, but we are also installing a small wood stove—the smallest model made by Jotül—for use on exceptionally cold nights.

The indoor unit of our heat pump is about 43” long by 13” tall by 9-3/8” deep and installed high on a wall extending in from the west wall of the house—next to an open stairway to the second floor; it is controlled with a hand-held remote. The outdoor unit, installed just off a screen porch on the west side of the house is 35” tall by 33” wide by 13” deep. It is under an overhang and held off the ground by granite blocking.


Indoor unit installed.
Photo Credit: Alex Wilson

ARC Mechanical from Keene, New Hampshire did a great job with installation, and the system has now been turned on. We won’t move in until December, but it’s nice to know we have heat.

See also Putting the Duct Back in Ductless Mini-Splits, and 7 Tips to Get More from Mini-Split Heat Pumps in Colder Climates.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-10-22 n/a 17808 Our Deck Is Made from Pallets—But It's Not What You Think

Viridian tropical hardwood decking is reclaimed from shipping materials—and it should last decades

Installing Viridian decking on our front porch. Click to enlarge.
Photo Credit: Alex Wilson

We’re moving along with some of the wrap-up work on our house in Dummerston. One of those projects is installing the porch decking on both the front and rear porches and a handicapped ramp up from the garage to the back porch. (We plan to live there for a long time!)

For the decking, we used a product we recognized in our annual Top-10 Green Building Product selection last year.

The Viridian story

Viridian Wood Products produces tropical hardwood flooring, decking, paneling, and countertop material derived from salvaged wood sources, including tropical hardwoods. I have long been a firm believer that one should only use wood from tropical rainforests that comes from well-managed forests—and certified to Forest Stewardship Council (FSC) standards—or that is salvaged from other uses and diverted from the waste stream.

Back in 2004, Joe Mitchoff and Pierce Henley of Portland, Oregon, noticed that a lot of wood used for shipping manufactured goods—especially heavy iron and steel—was being landfilled at the Port of Portland. As many as thirty 30-yard roll-off dumpsters per ship of mostly four-by-fours were going to the landfill, and they recognized that this was amazingly beautiful tropical hardwood.

As many as thirty 30-yard dumpsters of wood waste are generated from each ship bringing iron and steel from the Far East.
Photo Credit: Viridian Wood Products

Mitchoff and Henley made arrangements with the Port to divert that waste—saving the Port disposal costs—and they figured out how to process the wood cost-effectively, milling it into a high-end flooring and countertop material, while recycling the comingled waste.

While I referred to this material earlier as "pallets," it's important to note that most or all of the material used by Viridian is blocking or "cribbing" used to stablize shipped goods. There is a lot of wood waste in pallets, more narrowly defined as the flat shipping structures often used by forklifts, but they are riddled with ring-shank nails and are far less cost-effective to reciaim. 

The wood waste is first heat-treated to kill any invasive insects that may be living in it (shipping materials have been one of the main routes of entry for invasive insects getting into the United States), then scanned for metal fasteners, kiln-dried, and milled into standard dimensions for the various markets they serve.

With the high volume of production and a 40,000 square-foot warehouse next to the Port, Viridian Wood Products has been able to achieve a dependable supply, which is critically important for nationwide marketing of salvaged wood products. The company has even expanded into other reclaimed wood sources—such as Douglas fir salvaged from high school bleachers, Douglas fir from structures in the Pacific Northwest, a rustic oak salvaged from truck decks, and old-growth redwood salvaged from wine casks.

Dumping tropical hardwood shipping material at the Viridian warehouse.
Photo Credit: Viridian Wood Products

Jakarta Market Blend

Because Viridian’s tropical woods are reclaimed rather than being cut from forests, the species vary widely and typically aren’t even known. We ordered a mix of wood known as Jakarta Market Blend – Dark Sort that is comprised of probably at least a dozen actual species. Some are very dark, almost black; others are a deep red; some have beautiful figured grain. The weight also varies greatly, with some having specific gravity that is significantly greater than that of water—in other words, this is wood that won't even float.

The great density of these tropical hardwoods also results in tremendous hardness and wear properties. With flooring, hardness is typically measured using the Janca Scale. The Jakarta Market Blend – Dark Sort flooring we got has a hardness ranging from 1100 to 3500, which makes it suitable for high-traffic commercial applications. By comparison, eastern white pine has a hardness of 380, hemlock 500, Douglas fir 660, cherry 995, teak 1155, red oak 1290, and sugar maple 1450.

As we were selecting from the batch of wood received from Viridian, I chose the heavier pieces for the porch flooring—so I suspect most pieces have a hardness well over 2000. The dimensions of the decking are 2-1/2” x 5/8” with random lengths up to 6-1/2’.

Installing decking on what will be our screen porch on the back of the house.
Photo Credit: Alex Wilson

FSC certification

All Viridian reclaimed wood is certified according to FSC standards. FSC has standards both for virgin wood (relating to forest management practices) and for salvaged wood. All Viridian product carries chain-of-custody certification according to FSC’s 100% Post Consumer Reclaimed standard. The chain-of-custody certification number for Viridian Reclaimed Wood is SW-COC-001962.


While the wood will gray over time, I wanted to treat it with an oil finish that would bring out and retain for at least a while the gorgeous colors in the wood, but I also wanted to use a natural finish that was environmentally responsible. I chose a product called Heritage Natural Finish. I found out about this oil finish at the Timber Framers Guild of North America Annual Meeting this summer, where I was giving a presentation on our house.

Heritage finish (which used to be called Land Ark Natural Wood Finish) is made from naturally processed linseed oil, tung oil, beeswax, pure citrus solvent, and pine rosin. Unlike some oil finishes, there are no heavy metal drying agents or petroleum products. We used Heritage’s Exterior Finish, which include a UV inhibitor and a mildewcide to inhibit mold staining. (The Original Finish does not include the mildewcide.)

Decking detail on our front porch.
Photo Credit: Alex Wilson


Don’t even think about installing Viridian Jakarta Market Blend flooring without pre-drilling. Eli Gould’s crew started out drilling as they might for standard decking—with slightly undersized holes, but they were breaking off the stainless steel decking screws right and left! This stuff is hard!

We installed ours on framing made of TimberSIL, a totally nontoxic pressure-treated lumber. With TimberSIL, sodium silicate is infused into the wood under pressure, and the wood his then heated in a kiln, which melts the sodium silicate into an amorphous glass. This glass surrounds the wood cells, protecting it from decay and insects and well as imparting fire-resistance.  


Viridian is a premium product that sells for a premium price. Pricing is somewhat higher than that of redwood decking and significantly more expensive than pressure-treated (PT) decking. But it should hold up as well as Ipé, which is typically more expensive. The price of the Jakarta Market Blend is $6.95 per square foot, though shipping will add to the price. According to Joe Mitchoff, one of the advantages of having a constant supply of salvaged wood is the ability to keep pricing fairly constant.

Pre-drilling with holes the full diameter of the screws is necessary for installing the densest of the Viridian Jakarta Market Blend decking.
Photo Credit: Alex Wilson

The TimberSIL framing we used is also more expensive than standard PT framing, but we think it will last a lot longer, helping us (and our children and grandchildren) achieve the long life that we are seeking with the house.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-10-15 n/a 17801 Resilient Design on the U.N Agenda As It Prepares for Climate Change

The United Nations, climate change, and resilient design: a day at the U.N. World Habitat conference

The UN assembly hall where we met. Click to enlarge.
Photo Credit: Alex Wilson

The United Nations Human Settlements Programme, or UN-Habitat, is a UN agency focused on human settlements. It was launched in 1978 following a meeting in Vancouver known as Habitat I, and it is mandated by the UN General Assembly to promote socially and environmentally sustainable towns and cities with the goal of providing adequate shelter for all. A follow-up conference, Habitat II, was held in Istanbul, Turkey in 1996, and Habitat III is planned for 2016.

I had the honor of speaking last week at the UN World Habitat Day conference, “Resilient Design for Sustainable Urbanism.” The event was cosponsored by the Consortium for Sustainable UrbanismAIA New York, and the NJIT Center for Resilient Design. (What's resilient design all about? See Resilient Design—Smarter Building for a Turbulent Future.)

It was an amazing opportunity to see the United Nations; I think I was last there over 40 years ago. The UN Headquarters Complex is going through a major $2 billion facelift that includes many exciting green features that are supposed to achieve 50% energy savings, 40% water savings, and a 45% reduction in the carbon footprint…. But that’s not the focus of this column.

Harni Nagendra, a Ramanujan Fellow at the Ashoka Trust for Research in Ecology and the Environment in Bangalore, India, spoke on biodiversity in densely developed cities.
Photo Credit: Alex Wilson

Growing interest by the UN in climate change impact

The conference last week was one of a number of events leading up to Habitat 3, and it reflected a growing interest by the UN in climate change, rising sea levels, and the impact these changes will have on urbanization.

The day started off with an all-star cast. UN General Secretary Ban Ki-moon from South Korea opened up the program and described the UN’s deeply held concerns about climate change and commitment to both sustainability and resilience. Ki-moon was followed by John Ashe of Antigua and Barbuda, president of the UN General Assembly; Néstor Osorio the Columbian Representative to the UN and president of the UN Economic and Social Council; and Dr. Joan Clos of Spain, the Executive Director of UN-Habitat.

Shaun Donovan, the Secretary of HUD in the U.S. and chair of the federal Hurricane Sandy Rebuilding Task Force, was supposed to deliver the keynote, but could not due to the U.S. federal government shutdown. (How embarrassing to see such a poignant display of American dysfunctionalism on the international stage!) In his place was Henk Ovink, the former director general for Spatial Planning and Water Affairs for the Netherlands—and currently on loan to the U.S. for the above-mentioned task force.

Morning and afternoon panels dug more deeply into various aspects of resilient design. In the morning panel I described how our vulnerabilities extend well beyond sea level rise and coastal flooding to such issues as more intense storms, inland flooding of valleys (as we saw with Tropical Storm Irene here in Vermont), tornados, ice and snow storms, drought, wildfire, solar flares, and such anthropogenic issues as terrorism and political upheaval. I described a number of secondary impacts of these events, including prolonged power outages interruptions in gasoline supply or an ability to pump gasoline. Finally, I presented the Resilient Design Principles that have recently been published by the Resilient Design Institute.

That's me on the left side of the podium...intimidated!
Photo Credit: Wendy Brawer

Solutions elusive

While all of us on the podium did a reasonable job articulating the challenges we face from sea level rise and climate change, effective solutions remain elusive.

Some solutions were offered, surprisingly, by Dawn Zimmer, the mayor of Hoboken, New Jersey, just across the Hudson River from Manhattan. I say “surprisingly,” because I remember the photo of perhaps 100 taxis submerged there by Sandy’s storm surge. I had been under the impression that Hoboken was far less prepared for flooding than New York, where Mayor Bloomberg has been at the forefront of disaster preparedness. But she told us of some amazing planning underway in the City, such as efforts to provide for safe bicycle commuting through the Lincoln Tunnel and other strategies to get cars off the streets.

Henk Ovink noted that simply building things back to what they had been in the aftermath of storms like Sandy or Katrina is a lost opportunity. We need to learn from these disasters and respond appropriately. “Let the past be an inspiration for the future,” he told us in the afternoon.

One of the most inspiring presentations was by Nancy Kete, the managing director of the Rockefeller Foundation, which just announced a $100 million program to support 100 cities around the world in developing and implementing plans for urban resilience over the next three years. The foundation will provide technical support and financial resources in this remarkable program.

A reception following the conference looking out across the East River from a fourth-floor deck at the UN.
Photo Credit: Alex Wilson

The full presentations from the conference are available online on the NJIT Center for Resilient Design in three video segments.

There is much to do in addressing the multiple challenges of rising seas, more intense storms, and other impacts of climate change.

While in the U.S. one can lose sight of just how seriously most of the rest of the world is taking climate change, the UN’s leadership with climate change, not only with science (see the just released 5th Assessment Report from the International Panel on Climate Change) but also initiatives to do something about these challenges, gives me hope that progress can be made.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-10-09 n/a 17786 New Home Proves LEDs Are Ready to Supplant Older Lighting

LED lighting has come a long way in a very few years and can now fully supplant incandescent and fluorescent technology

Cree's new CR6 LED downlight for recessed cans.
Photo Credit: Cree

Our electrician was in last week installing lighting in our new home here in southern Vermont. Virtually all of our lighting will be LEDs—the state-of-the-art today in energy-efficient lighting.

LED stands for “light-emitting diode.” It’s a solid-state lighting technology that converts electric current directly into visible light. LED lighting has far higher efficacy (the number of lumens of light output per watt of electricity consumed) than incandescent lighting—which converts roughly 90% of the electric current into heat; only 10% into light.

Most LED lights also have modestly higher efficacy than compact fluorescent lamps (CFLs). The recessed LED lights we installed have an efficacy of 66 lumens per watt, which is not to different from that of CFLs, but LEDs are much more directional than CFLs, so they work better in recessed cans in delivering usable light to where you need it.

A CR6 installed in our access ceiling.
Photo Credit: Alex Wilson

Very significantly, LEDs are also better for the environment and human health than fluorescent lamps. With fluorescent lamps (both linear and compact), an arc of electricity passes through mercury vapor, which produces ultraviolet (UV) light; that UV is then turned into white light using a phosphor coating on the inside of the fluorescent tube.

Any time a fluorescent lamp breaks a small amount of elemental mercury escapes into the building; the mercury also gets into the waste stream when the lamps aren't properly recycled. While the elemental form of mercury is far less dangerous than compounds in which the mercury is bonded to carbon-based organic compounds, there is still risk.

Mercury is also needed in the metal halide and high-pressure sodium lamps that are common on highways and parking lots.

The other advantage of LED lights is the expected life—typically 25,000 to 50,000 hours, which is far longer than the 1,000 to 3,000-hour life of incandescent light bulbs and somewhat longer than most CFLs and linear fluorescents (10,000 hours for the former, 15,000 hours for the latter). I won’t quite believe the long-life claims for a few years, though; I’ve installed a number of early LED lights that failed prematurely after less than a year.

Recessed can in our access ceiling.
Photo Credit: Alex Wilson

Cree at the leading edge

There are lots of LED lights on the market—and more appearing all the time. The products we installed are made by an American company, Cree, which is based in North Carolina and continues to be one of the world’s top innovators with LED technology.

I first became familiar with Cree in 2007 when we recognized a breakthrough downlight product from LED Lighting Fixtures (LLF), as one of our Top-10 Green Building Products of the year. LLF incorporated LEDs made by Cree into their downlights, which set the bar for light quality from LEDs, and really established LED technology as a viable high-quality light source.

Shortly after that, Cree acquired LLF and entered the light fixture business—in addition to being a supplier of LEDs to fixture manufacturers.

Ongoing product innovation and a key company acquisition in 2011 of Rudd Lighting and their subsidiary company BetaLED, which has been the technology leader with outdoor LED lighting, has kept Cree at the front of the pack in the LED world.

The actual LEDs used in Cree lights are made in the U.S., though most if not all of the company’s fixtures are now produced elsewhere—no doubt to reduce costs and stay competitive.

Cree SL40 linear LED troffer in our basement.
Photo Credit: Alex Wilson

Downlights, surface lights, and light bulbs

We will have three types of Cree LED lights in our house: CR6 downlights installed in recessed cans in our ceilings; SL40 linear LED lighting fixtures for our garage and basement; and the new LED light bulbs that were introduced this year. The latter will be installed in light fixtures that can accept incandescent light bulbs, and those have not been installed yet.

But the downlights and surface-mount fixtures are in place and working beautifully.

The CR6 downlights are designed as retrofit lamps for six-inch recessed cans with Edison sockets that accept standard screw-base incandescent (including halogen) lamps. Cree also makes a version for the GU24 base, which is required for Title 24 compliance in California (because that type of lamp can’t be swapped for a less-efficient incandescent light bulb).

The CR6 lamps we installed use 9.5 watts to produce 625 lumens, which works out to just under 66 lumens per watt (lpw), though the Cree literature lists the efficacy as 61 lpw. This lamp is available in different color-temperatures (see Shedding Light on Light Quality). We opted for warm-white light with a color temperature of 2700K (lamps with cooler, whiter light, at 3000K, 3500K, and 4000K, are also available). In terms of light quality, the CR6 has an excellent color rending index (CEI) of 90. The light quality seems much like that of incandescent lighting that most people prefer in homes.

One of our SL40s with the light turned off.
Photo Credit: Alex Wilson

The Surface Linear, SL40, fixtures we installed function much like standard fluorescent fixtures that mount on a ceiling, but they’re more elegant and use LED technology. Ours are 40 inches long and consume 55 watts while producing 4,000 lumens (73 lpw). The light, with a color temperature of 3500K, is somewhat cooler than our CR6 recessed lights, but seems just fine for where we are using them. The light quality, with a CRI of 80, isn’t as high as that of the CR6, but it’s respectable—and comparable to most fluorescent lights.

This year, Cree has been making news with LED light bulbs designed to replace standard incandescent and screw-in CFLs. In March, 2013 the company introduced 60-watt and 40-watt equivalent bulbs (using 9.5 and 6.0 watts, respectively, for the warm-white version). Delivering 800 lumens using just 9.5 watts, this lamp has an amazing efficacy of 84 lpw. A cool-white version has an efficacy of 89 lpw.

While that lamp has a CRI of 80, just this month the company introduced a brand new TW (for True White) version with a remarkable CRI of 93. But in the soft-white (2700K) version, this lamp has an efficacy of only 59 lpw. To get the high light quality there is some sacrifice in efficacy.

Not only Cree

The most exciting thing about LED lighting today is that Cree isn’t the only innovator. There is intense competition by other companies, including Philips, who are driving the entire industry forward at a rapid pace. Light quality will keep improving while energy consumption will deep on dropping.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-10-02 n/a 17731 A Passive House Movement Grows in Brooklyn

A three-unit condominium project under construction in Brooklyn is one of many Passive House projects that are springing up in the Borough

The unit on the right, constructed of ICFs, is expected to achieve Passive House certification
Photo Credit: Alex Wilson

I was in New York City over the weekend where I spoke at the Annual Meeting of the Northeast Sustainable Energy Association. What I most relished about the trip was an opportunity to explore a new infill housing project in Brooklyn that’s being built to Passive House standards and may well achieve net-zero-energy performance.

Passive House is a certification system that originated in Germany and has been picking up steam over the past few years in North America. To achieve certification, buildings must have modeled energy performance that does not exceed a very stringent limit for heating and cooling as well as total annual primary energy consumption below a specified threshold.

Getting a glimpse into New York’s Passive House community

It was actually through my daughter that I got to know builder Ray Sage, of Race Age, Inc., and architect Paul Castrucci, of Castrucci Architect. In addition to building high-performance buildings, Ray manages some rooftop beehives in East Village from which he harvests honey; my daughter was writing an article about raising bees in the City for her CSA (community supported agriculture) newsletter and spent an afternoon with Ray, his wife Wendy Brawer (who runs GreenMap, a nonprofit network that produces maps of cities highlighting green living resources), and their friend Paul, to learn about beekeeping and help out with honey extraction.

The first connection with builder Ray Sage was through his bees--on a rooftop in the East Village of New York.
Photo Credit: Alex Wilson

Somehow the topic of green building came up, and it turned out that Ray and Paul were both familiar with my work with Environmental Building News. Ray and Wendy came to my Saturday evening lecture, and I was invited to visit the R-951 Residence, their three-unit Passive House condominium project under construction in the Prospect Heights neighborhood of Brooklyn.

Along with working together on honey extraction, Paul, Ray, and Wendy are partners in Further, Inc., a design-build firm specializing in sustainable building, and the developer of R-951.

A four-story, three-unit walk-up

Being built on a narrow lot in a neighborhood of three- or four-story row houses, R-951 (named for resilience, R-value, and the address: 951 Pacific Street). The three-unit row house is tall and narrow, but with a remarkable amount of outdoor space. The first-story apartment includes a sizable backyard along with half of the basement space (the rest being common space for the three units). The second-story apartment includes a small front balcony and larger rear balcony plus an upper-level loft bedroom. The upper unit is also on two levels and includes front and rear rooftop terraces along with a small front balcony.

Secton of R-951 showing the three multi-level apartments and extensive outdoor space. Click to enlarge.
Photo Credit: Castrucci Architects

Each unit is about 1,500 square feet. Because the project is designated as a green building by the City, there was a 500 square-foot bonus provided to the developed area. “That is huge,” Paul told me, in that it allowed the addition of the terrace space.

The building is insulated with insulated concrete forms (ICFs) and lots of additional polyisocyanurate foam insulation. The exposed north and south walls are insulated to about R-46, the roof is insulated to R-59, and there is R-21 insulation under the basement slab.

Windows are state-of-the-art triple-glazed, vinyl-framed Schüco units from Germany with NFRC U-factors of 0.15 and remarkable 0.71 visible transmittance. In other words, these windows allow less than half as much heat loss as standard, American double-glazed windows with low-emissivity glass and argon gas fill), yet they are just as clear or even clearer. The solar heat-gain coefficient (SHGC) is 0.50—allowing plenty of solar gain for passive solar heating benefits.

The Schüco windows provide visible transmittance of over 70% with unit U-factors of 0.15.
Photo Credit: Alex Wilson

Preliminary energy modeling using the Passive House Planning Package (PHPP), done by Grayson Jordan in Paul’s office, came out at 4.80 kBtu/ft2·year, which is slightly higher than the Passive House threshold (4.75 kBut/ft2·yr), but Paul thinks that with some tweaks to the envelope during construction the project will help them meet the Passive House requirements.

Indoor air quality will be ensured with the highest-efficiency heat-recovery ventilators on the market—those made by the Swiss company Zehnder (the same product we’ve installing in our house). As with our house, the small-diameter round ducts are snaking through R-951 by the dozens.


The building is all-electric. A Mitsubishi mini-split air-source heat pump provides heating and cooling for each apartment. Hot water will be provided with Stiebel Eltron heat-pump water heaters, which I believe are the highest efficiency heat pump water heaters on the market. Induction cooktops and electric ovens will be used in the kitchens. Jordan Goldman of Zero Energy Design, consulted on building science and mechanical systems design for the project.

A rooftop solar array will provide a total of 12.2 kilowatts (kW) of solar electricity (4.2 kW for one unit and 4.0 kW for each of the other two). These will be net-metered systems that “spin the meter backwards” when the system is producing more electricity than the apartment is using. The solar system is being installed by AEON Solar and will tie into the Con Edison power grid.

The solar system will not include battery back-up, but will use SMA’s new transformerless inverters with access to some power when the utility grid is down and the sun is shining. I wrote about this new inverter last month, and love the resilience benefits it provides.

High-efficiency Zehnder HRVs will ensure good air quality in the apartments.
Photo Credit: Alex Wilson

The solar system will come close to making the project net-zero-energy, but whether it actually gets there will depend on how efficiently the homeowners operate their apartments.

The cost for all these added features to achieve Passive House performance is about 5%, according to Ray, though such a small surcharge for the green features in part reflects the generally high construction cost of multi-unit condominiums in Brooklyn.

Ray, Wendy, and Paul anticipate that these features may boost the selling prices slightly compared with standard condos in the neighborhood—one of which is going up next door (with a common wall) and offers a clear comparison.

You can watch the project take shape at

Burgeoning interest in Passive House

After our visit to R-951, Ray, Wendy, and I drove through a few neighborhoods of Brooklyn looking at a number of other projects that are currently being built or renovated to achieve Passive House certification—and one being built to the Passive House performance standards, but that will not be certified (because the owner wanted a fireplace). And these projects were all within a few blocks of R-951.

I was amazed to learn of so much activity. In fact, Wendy told me that there are over 700 members of the NY Passive House MeetUp Group! That doesn’t mean that all those people are actually building Passive House projects, but clearly there is a great deal of interest.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-09-25 n/a 17721 Serenbe: A Solar-Powered Development Trying to Solve Car Dependence

With EarthCraft certification being a requirement, energy performance of homes in Serenbe is relatively good; transit options being planned will also help save energy.

The net-zero-energy Bosch Demonstration Home at Serenbe.
Photo Credit: Alex Wilson

After bringing some of the unique features of Serenbe, a New Urbanist community outside Atlanta, to you last week, today I’ll describe some of the energy features at the 1,000-acre development.


Serenbe is an EarthCraft Community, meaning that 100% of homes and commercial buildings must be built to EarthCraft standards. EarthCraft is one of the nation’s most successful regional green building programs. Developed by Southface in Atlanta, EarthCraft now boasts over 40,000 certified homes and a new commercial-building certification program.

EarthCraft energy standards aren’t close to those of the Passive House certification, but they are reasonably good and have done a great deal to improve the energy performance of homebuilding in the Southeast. The program requires blower door testing and has served to introduce this and other elements of high-performance building to the mainstream building industry.

One sees quite a few PV modules when walking around Serenbe.
Photo Credit: Alex Wilson

While EarthCraft compliance is the baseline for Serenbe, many homes go beyond that. Just completed a few weeks before my visit is the Proud Green Home, a project with numerous partners, including Southface, that is certified to Earthcraft Platinum standards, which are much more stringent than simply Earthcraft certified.

Net-zero-energy homes

Some homes at Serenbe are going well beyond even Earthcraft Platinum requirements. There are several net-zero-energy homes already built among the 140 completed homes and townhouses. “Net-zero-energy” means that solar-electric modules on a house provide all of the energy that home requires. Most of these all-electric homes rely on ground-source or water-source heat pumps (referred to by many, including Serenbe, as “geothermal” heating systems).

I’m usually not a huge fan of ground-source heat pumps. I’d rather put the money that would be spent on coils of tubing into the building envelope to reduce heating and cooling loads, then satisfy the remaining demand with much less expensive mini-split air-source heat pumps.

Steve Nygren, the developer and visionary behind Serenbe, pointed out to me several areas where clusters of net-zero-energy homes will be built, along with some net-zero-energy commercial buildings.

Walking around the development, one sees quite a few houses with solar-electric modules on their roofs, so even if net-zero-energy performance isn’t being obtained, such homes are at least relying on renewable energy for some of their energy demand.

The Proud Green Home at Serenbe.
Photo Credit: Alex Wilson

Leaving the car at home

Lots of features at Serenbe are designed to encourage alternatives to the automobile that would reduce the transportation energy intensity of buildings there. Through wide sidewalks, traffic-calming features that improve pedestrian safety, and extensive pathways in the community, Serenbe is designed to be a pedestrian-friendly community that works well for walking and bicycling. These measures will be more successful at reducing car use, however, once there are more services and commercial space available in the Serenbe town centers.

For self-employed residents, I’m told that Serenbe is also a great place to live—and it has attracted quite a few such individuals.

Chattahoochee Hills, the recently formed municipality that includes Serenbe, is also developing a regional network of trails that will make longer-distance bicycle transportation more realistic—to surrounding towns and communities.  

The reality, however, is that for many residents, Serenbe is a bedroom community for Atlanta. For residents who work in the city, commuting by car is still the only option. That could change, though. Chatahoochee Hills has maintained a right-of-way for future transit along the South Fulton Parkway, Nygren told me.

The Bosch Experience Center.
Photo Credit: Alex Wilson

Serenbe is also about five miles from Palmetto, Georgia, where there is a plan to use an existing rail line for passenger rail service into Atlanta. If rail service were developed connecting Serenbe and other area towns with Atlanta, that could help to dramatically reduce energy use—and the carbon footprint—of residents in the community.

Nygren, the ultimate cheerleader for Serenbe (and a resident of the town), is optimistic about that happening.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-09-18 n/a 17608 Serenbe—A Unique Green Town in the Making

Developer Steve Nygren is putting New Urbanist principles into practice at the Serenbe Community outside Atlanta

A wide range of architectural styles are represented at Serenbe. Click to enlarge.
Photo Credit: Alex Wilson

I’m just back from Atlanta, where I spoke on Saturday at the new Bosch Experience Center located in the unique Serenbe Community thirty miles southwest of Atlanta.

I gotta say, I was impressed!

Serenbe is the creation of Steve Nygren, who was kind enough to show me around and point out some of the community’s green features after my presentation. It is a 1,000-acre new town development that is one of the best examples in the country today of what a green development can be.

For starters, the larger area—about 62 square miles—was incorporated by Nygren and some other developers as its own municipality, the City of Chattahoochee Hills, allowing them to establish some highly unusual zoning regulations. For example, at least 70 percent of the land in any development must remain as open space, which can include agriculture, recreation, or natural area.

Naturalized wetlands for sewage treatment

This constructed wetland treats all of the wastewater at Serenbe.
Photo Credit: Alex Wilson

Before my presentation Saturday morning I explored some of the wild areas at Serenbe—or at least I thought they were wild. When I later talked with Nygren, he explained that part of the area I had walk through is actually an extensive constructed wetland for wastewater treatment.

Michael Ogden, of Biohabitats, headquartered in Baltimore, Maryland, whose work I have long admired, designed this system, which will be able to treat the wastewater from all 220 homes and townhouses once build-out is complete, along with two schools and significant areas of commercial development. Rather than being cordoned off with chain link fences, as one might expect with wastewater treatment, this sewage treatment area hosts a network of trails and a boardwalk for all to enjoy. (The wisdom of using onsite wastewater treatment at the community level rather than with a single building is explored in our feature article, Waste Water, Want Water.)

Biophillic features

Nygren appreciates nature and wants to facilitate greater appreciation of our outdoor environments. He is creating at Serenbe an institute focused on biophilia to promote and teach about biophilic features of land use. (Biophilia, a termed coined by Harvard biologist E. O. Wilson, is the innate affinity—or love—that humans have for nature.) Much of the landscaping in the development reflects this priority. I spent a while Friday afternoon photographing swallowtail butterflies on some gorgeous plantings of butterfly bush by the Inn at Serenbe and the Farmhouse Restaurant.

Traffic calming and edible landscaping are both provided by these curb bump-outs planted with blueberry bushes and fig trees.
Photo Credit: Alex Wilson

Many of the traffic-calming bump-outs (extensions of curbs into the streets to slow traffic and demark on-street parking) are planted with edible landscaping. Nygren told me that the blueberry bushes and fig trees are favorites for the students who attend the Montessori school next to the Bosch Experience Center. Fruit trees that have been planted there will become popular as they reach fruit-bearing age.

New Urbanist development patterns

Conventional development today is sprawling, with each home served by a driveway and usually a garage facing the street; most houses are on cul de sacs, which discourage walking. At Serenbe, the houses are located right along the streets, with on-street parking in front and, often, alley access behind. Townhouses provide greater density and more urban feel in the town centers of the community.

Saturday afternoon, as I was leaving for the airport, a “tailgate party” of Georgia Tech football fans with a live band on one of the homes’ porches, had spilled out into the street as an impromptu block party—something the community is designed to encourage.

These townhouses include passive cooling features.
Photo Credit: Alex Wilson

Many of these buildings feature live-work arrangements with commercial or retail space on the street level and apartments above. I stayed in a very pleasant in-town apartment that is managed by the Inn at Serenbe. After working on my presentation in my room Friday night, I walked downstairs and down a few doors on the sidewalk to discover a musician performing at the Blue Eyed Daisy Bakery Café.

I bought a beer and joined the 20 or so others enjoying the music. It isn’t quite the East Village, but I can see how this will become a more and more vibrant area as the build-out continues.

Serenbe is different from Seaside, probably America’s most famous New Urbanist town (on Florida’s panhandle). Serenbe is more spread out, with a lot more open space that separates the higher-density neighborhoods and three town centers (the construction of one of which has yet to begin). To get from one neighborhood to another some people drive (either by car—15 mph speed limit, controlled by rather robust speed bumps—or electric golf carts, which are very popular). An extensive network of trails also connect these areas.

Developer Steve Nygren in front of a 1,400 square-foot model "Nest Home" at Serenbe.
Photo Credit: Alex Wilson

As more of the development is completed at Serenbe, I think it will gain more of a “critical mass” feel. Nygren pointed out places where clusters of additional homes will be built, along with several hundred thousand square feet of commercial space, including retail shops, offices, a hotel, and (notably) a brew-pub.

Farming at Serenbe

It was partly out of an interest is supporting local agriculture and food-to-plate initiatives that Serenbe was first created. Currently eight acres of land are being actively farmed in a certified organic and Biodynamic operation, and 25 acres are set aside for farming. The farm is managed by Paige Witherington with several interns, and it supplies food to a 125-person CSA (community-supported agriculture operation), the Saturday farmers market in one of the town centers, two acclaimed restaurants at Serenbe, and the Blue-Eyed Daisy Bakery. (Read more on integrating agriculture into the built environment.)

There are also horse pastures and stables, with trails extending through the undeveloped portions of the property.

Next week I’ll cover some of the energy features at Serenbe, includng a look at the transportation footprint of the project, relative to commuting and tying into mass transit.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-09-11 n/a 17583 As Vermont's Only Nuke Plant Closes, Is a Green Economy Ready?

The pending closure of Vermont’s only nuclear plant will hurt the local economy, but it could catalyze sustainable economic development

The Entergy Vermont Yankee nuclear power plant will be shut down in late 2014. Click to enlarge.
Photo Credit: U.S. Nuclear Regulatory Commission

The big energy news in my part of the world this past week has been the pending closure of Vermont’s only nuclear power plant, Vermont Yankee, in Vernon, about six miles south of Brattleboro. The closure is scheduled for the fourth quarter of 2014, at the end of the current fuel cycle.

For a lot of my friends, this was news that they had been hoping for for many years and a cause for celebration. I share with these individuals concerns about nuclear power, especially a fear that nuclear power plants could be targets for terrorist actions. So I feel some relief that after another year or so there won’t be new radioactive material generated ten miles from my house—though the high-level radioactive waste that’s stored onsite could remain there for decades.

But for me it’s a more complicated issue.

Our economy in Windham County, and especially the Brattleboro area, benefits significantly from Vermont Yankee (VY). The plant directly employs over 600 people in the tri-state area, with an annual payroll of $66 million and an average wage of slightly over $100,000. This represents 5% of Windham County’s total payroll.

And there are many cascading benefits of the plant to the region’s economy. According to the Brattleboro Development Credit Corporation (BDCC), in addition to VY’s employees an estimated 400 positions in the region are supported indirectly by the plant: local motels, restaurant workers, retail sales positions, etc. And Entergy Vermont Yankee and its employees give a lot to local nonprofit organizations, including United Way of Windham County—where VY is the largest contributor.

Our economy will suffer from the plant’s closure; there’s no getting around that.

Seeking that silver lining

But the closure also offers opportunities. It could be a rallying point for a new, greener focus on regional economic development. Indeed, for the past several months I’ve been part of an initiative of BDCC and Southeastern Vermont Economic Development Strategies (SeVEDS) to identify and strengthen an emerging “green products and services industry cluster” for southeastern Vermont.

We held a meeting in June with about a dozen business owners and leaders in the green building and energy efficiency sectors to discuss how to derive long-term, sustainable, economic growth in this area—including both manufacturing and service-sector jobs—and there will be a follow-up meeting next week.

The 2014 closure of the plant could provide key momentum toward sustainable economic development in the region. It could also stimulate renewed discussion about the broader issues of power generation and centralized vs. distributed power production.

VY is closing largely because of the low cost of natural gas, which has become the preferred energy source for utility companies. As I’ve written in a previous column, the same fate is befalling some of the nation’s dirtiest coal-fired power plants—and that’s a good thing.

In the short term, the low cost of natural gas may hurt renewables, because utility companies are choosing to build new natural gas plants rather than invest in distributed renewables. But once the price of natural gas goes back up—as I believe it will once demand catches up with supply within the next decade—utilities will find that investing in solar, wind, and other renewable energy systems is less expensive than building new coal or nuclear plants. At least that’s my hope.

What to do with the old VY plant

Meanwhile, the discussion about decommissioning the Vermont Yankee power plant in Vernon is ramping up. At one end of the spectrum is the prospect of SAFSTOR (essentially putting the plant into a long-term holding pattern—up to sixty years—before dismantling it and restoring the site).

I’d much rather see decommissioning begin as soon as possible, so that we can look into how that site could be reused. Unlike some, I’m not optimistic about replacing Vermont Yankee with some sort of renewable power plant, such as a wood-chip-fired power plant that would take advantage of the power distribution lines extending to the plant. Such power plants, I believe, should only be built in locations where the waste heat can be captured and productively used. (See In the Pipeline:District Energy and Green Building).

Such co-generation or combined heat and power (CHP) systems, in which the waste heat from thermo-electric power plants is recovered, are where we as a nation need to be going with centralized power generation. It is ludicrous that we throw away two-thirds of the primary energy as thermal pollution with conventional power generation. But it would be hard to build a CHP plant in Vernon, much as I’d like to see that happen, because of the distance hot water would have to be piped to buildings and industrial facilities where it could be used.

This doesn’t mean that we shouldn’t decommission and clean up the VY site as soon as possible, however. That should be our priority, which will also provide a several-year spurt of economic activity in the region. That could help us in the longer-term transition to sustainable economic health built on the energy efficiency and green building sector.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-09-04 n/a 17525 A Heat Pump Using Carbon Dioxide as the Refrigerant

A new generation of CO2-based heat pumps could avoid the high global warming potential of standard refrigerants and generate much higher temperatures

A Mayekawa Unimo air-to-water heat pump installation in Australia. Click to enlarge.
Photo Credit: Mayekawa

In researching and writing about building products for Environmental Building News over the past twenty-plus years I’ve had an opportunity to cover some fascinating breakthrough products and technologies. One such technology I was writing about a few weeks ago is the use of carbon dioxide as a working fluid for heat pumps

But let me back up with a little context about refrigerants. These are the fluids used in refrigerators, air conditioners, and heat pumps that transfer heat from one place to another in cooling or heating a space. This “vapor-compression-cycle” equipment takes advantage of the principle that compressing a gas absorbs heat and expanding it releases heat—so it’s a way to move heat from one place to another.

When this compression and expansion cycle results in a phase change (converting it from liquid to gas or vice-versa), significant heat can be absorbed and released.

Problems with refrigerants

Over the past 35 years, refrigerants have come under fire—both for their impact on the Earth’s protective ozone layer and for their global warming potential (GWP). HCFC-22 (R-22), a hydrochlorofluorocarbon, has long been the most common refrigerant. But it is being phased out according to the international treaty to protect the Earth’s protective ozone layer.

That’s a good thing, as R-22 is both a significant ozone depleter and a significant greenhouse gas. The HFC (hydrofluorocarbon) refrigerants that have replaced HCFC-22 are much better from an ozone-depletion standpoint (ozone depletion potential or ODP of 0), but they are still very significant greenhouse gases (high GWP).

An EcoCute water-to-water heat pump (next to the large tank) at the Somerston Winery in Napa Valley, California.
Photo Credit: Mayekawa

Using CO2 as a refrigerant

These concerns with HCFC and HFC refrigerants have led to interest in other chemicals that can be used as refrigerants, one of which is carbon dioxide (CO2). The Japanese have focused considerable attention on CO2-based heat pumps, and one Japanese company, Mayekawa, has been selling commercial-scale CO2-based heat pumps in North America for several years.

Mayekawa offers three different CO2 heat pumps, the EcoCute water-to-water heat pump, the Unimo air-to-water heat pump and the Sirocco water-to-air heat pump. (The product name, EcoCute, got a little bungled in translation from the Japanese. “Eco” is short for “ecological” in the U.S., while ”cute” is derived from a Japanese kyūtō, meaning “supply hot water.”) The term “EcoCute” is used generically by a number of Japanese manufacturers.  

All three of the Mayekawa heat pumps have 25 kilowatt (kW) motors, so they are considerably larger than the heat pumps used for homes.

High efficiency is an important benefit of such systems; they operate at a coefficient of performance (COP) of about 4.0. If they are configured to provide space cooling in addition to hot water (just the water-to-water and air-to-water models), the COP can be as high as 8.0.

Higher output temperatures

From a performance standpoint, the big difference with CO2-based heat pumps is that they can produce much higher-temperature output. Exactly why they can do this is complex and has to do with CO2 being a “transcritical” refrigerant and doesn’t fully change phase like other refrigerants—described in detail in the article on Mayekawa heat pumps that I wrote for the August issue of Environmental Building News.

Detail of the EcoCute heat pump at the Somerston Winery, showing a large buffer tank.
Photo Credit: Mayekawa

The EcoCute water-to-water heat pump and the Unimo air-to-water heat pump can produce water at up to 194°F—far hotter than that produced by standard heat pumps. This is significant, because it makes them viable for hydronic (baseboard hot-water) heating. As my friend and energy engineer Marc Rosenbaum, P.E. told me, if this can be done affordably, it will be a “game changer.”

One challenge with CO2-based heat pumps is that they need a fairly large lift temperature to operate. This is the difference in temperature in a heating loop between the supply and return temperature.

A standard gas- or oil-fired boiler may deliver 180°F water for hydronic heating, and return water in the heating loop at a temperature of 150°F after delivering it’s heat through baseboard radiators. So the boiler has to “lift” the water from 150°F to 180°F. That isn’t enough lift for a CO2-based heat pump. The EcoCute needs a minimum of about 45°F of lift to function effectively.

Higher pressure

The other challenge is that CO2 refrigerant cycles operate at far higher pressure than standard vapor-compression-cycle equipment. At the evaporator side the pressure can be about 600 pounds per square inch (psi), while in the gas cooler (which replaces the condenser in a standard compression-cycle device), the pressure can be 1,500 to 1,800 psi.

The higher pressure and the need for more robust (and more expensive) components to contain that pressure has slowed the development of CO2-based heat pumps.

An EcoCute installation in Quebec, Canada with multiple units.
Photo Credit: Mayekawa

The future of CO2-based heat pumps

I gather that several manufacturers of popular mini-split heat pumps are developing residential-scaled CO2-based heat pumps and that those heat pumps are currently undergoing testing.

It will be fascinating to see what emerges. What excites me is that such heat pumps increase the potential of providing more of our energy needs using electricity generated by sunlight as an alternative to burning fossil fuels. There are challenges, certainly, but such products could help us transition to a solar future.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-08-28 n/a 17516 Access Ceilings: Replace Fixtures Without Cutting Into Drywall and Insulation

Paying attention to the various layers in a building envelope is critically important for ensuring air tightness and moisture management—and can be attractive, too.

Ducting for our HRV, electrical wiring, recessed lights, and plumbing fit into this access ceiling. Click to enlarge.
Photo Credit: Alex Wilson

Air leakage and the integrity of insulation in energy-efficient houses is a huge issue—more significant than many people realize. We can have the best of intentions with lots of insulation, but if we leave it leaky or include details that compromise the integrity of that insulation the home’s energy performance can be severely affected.

Take recessed ceiling lights, for example. From a design standpoint, they’re great, since the light source is roughly flush with the ceiling and all of the mechanism is hidden in the ceiling above (in recessed cans).

In a house with an unheated attic (insulation in the attic floor—which is the ceiling of the floor below) or with an insulated, sloped cathedral ceiling (roof), if we install recessed cans into that ceiling we’ve created a significant pathway for air flow and compromised the insulation. This is the case even with recessed lights rated for “insulation contact,” those IC-rated fixtures are far better than older models that required a significant air space surrounding the lights, but they still result in significant air leakage.

Creating an access ceiling that looks good

One of the solutions to this problem is to create an access ceiling (or drop ceiling) below the air barrier of the insulated ceiling. Recessed lights can be installed in such a ceiling. Lest images of acoustic ceiling panels in commercial office buildings come to mind, rest assured that access ceilings can be done in a very attractive way.

Tedd Benson has been doing this for years with Bensonwood homes using his OpenBuilt platform, and our designer-builder, Eli Gould, has his own access ceiling detail that he’s using in our Dummerston home. He’s using this layered, access ceiling detail on both the first floor ceiling (which is not insulated) and for a horizontal section of the second floor ceiling, spanning between the insulated sloped and insulated rafters.

Eli builds roughly square panels out of painted 1x10 shiplap boards—three boards per panel. These drop in and can easily be lifted up to access the recessed lights. On the first-floor ceiling, these panels fit into tracks formed by added beams that are both attractive and strengthen the ceiling joists.

Recessed lights are mounted in the access ceiling panels.
Photo Credit: Alex Wilson

Along with installing recessed lights in these ceiling panels, registers for our Zehnder heat-recovery ventilator are mounted there as well. The ceiling cavity above the panels provides a space to run wiring, ventilation ducts, and—in some locations—plumbing. Future modifications to any of this can be made very easily.

Air tightness also depends on layers in walls

Our superinsulated wall system has seven layers: from the interior there is the layer of gypsum board; the wall cavity with fiber insulation; a taped and air-sealed sheathing layer (using Huber’s Zip sheathing) that serves as the air barrier; a layer of exterior rigid insulation on the outside of the sheathing; a layer of waterproof but vapor-permeable housewrap (weather-restive barrier); a rain screen (vented air space) formed by vertical strapping; and finally, the factory-painted wooden clapboard siding.

By keeping the air barrier in the center of the wall—with cavity-fill fiber insulation on the interior—wires can be run through the that insulation without compromising the air barrier.

Effectively insulating a wall cavity with wires running through it should be done with something other than batt insulation. Cellulose insulation (dense-pack or damp-spray), fiberglass (dense-pack or spray), or spray polyurethane foam (closed-cell or open-cell) all fill well around wires. As I described in a blog a few weeks ago, for our house we used Johns Manville Spider spray fiberglass insulation, which has an acrylic binder to hold the insulation in place.

A ceiling panel made from three sections of shiplap pine.
Photo Credit: Alex Wilson

Wiring for wall outlets can also be contained in baseboard raceways. This is a detail that Benson uses with his OpenBuilt wall system—and one that Eli uses on some projects. It totally avoids running wires in the insulation, allowing easy modifications later, and it’s an ideal solution for panelized construction (in which wall panels are built in a factory and trucked to the jobsite). We considered such a system, but it would have added a lot of cost. 

With our air barrier in the middle of the wall, the cavity-fill insulation can dry to the interior, and the exterior insulation can dry to the exterior. This offers effective drying potential due to the "vapor profile," and More and more building science experts seem to be recommending this approach. We’ll find out how it worked—or someone will—in 20 or 50 or 100 years when a totally dry wall system with no rot will, I hope, be evidence of good moisture management.

Testing air tightness

We don’t yet know how good a job we have done with air sealing at our house. I’m hoping that we will end up with an air leakage rate as low as 1.0 air change per hour at 50 pascals of pressure difference (ACH50)—as measured by a blower door. That will be far tighter than the average new home being built today, but still considerably leakier than a house built to the rigorous Passive House standards—which require an air leakage rate of 0.6 ACH50.

Even if the news is embarrassing and we don’t get to 1.0 ACH50 I promise to report that here. If we don’t make it, it will likely be because some elements of our 200-year-old frame necessitated complex detailing with the sheathing layer or because we didn’t spend the money needed for the best Passive House windows and doors. But I’m optimistic.

Oh, and did I mention that the recessed cans in our access ceilings will contain LED lights? I’ll write about those in a future blog.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-08-22 n/a 17502 It Takes a Village to Be Resilient

Surveying residents to assess resilience in the town of Dummerston, Vermont

The solar-electric system on our restored barn will contribute to community resilience in our part of Dummerston, Vermont.
Photo Credit: Alex Wilson

The Dummerston Energy Committee, on which I serve in my home town, is conducting an energy survey.

Partly, we are conducting this survey to understand how our town uses energy—both in our homes and in getting around in our vehicles. We have a goal in Dummerston, articulated in our Town Plan, to reduce nonrenewable energy consumption 40% by 2030, and we’re trying to establish a baseline from which to measure our success in achieving that long-term target.

But we’re also conducting this survey for another reason that may be more important: to gauge how resilient our town is.

Vulnerabilities to power outages and other problems

Tropical Storm Irene in 2011 uncovered some vulnerabilities in Vermont. Heavy rainfall on saturated ground resulted in dramatic flooding in parts of Brattleboro, Wilmington, Halifax, Newfane, and other towns. Some communities were cut off for as much as a week. Other places lost power for an extended period of time.

Irene, of course, wasn’t the first storm to cause blackouts or close off roads, and it certainly won’t be the last. Such occurrences happen almost every year from ice storms, snowstorms, heavy rainfall, and derechos that knock down trees. Other parts of the country have to worry about wildfires, tornados, hurricanes, earthquakes, and tsunamis. Even drought and heat waves can contribute to power outages if power plants have to shut down due to lack of cooling water or cooling water that’s become too warm.

There is also concern about issues like political strife around the world, which could threaten heating oil or gasoline supplies, and terrorism, including hacking into the power distribution system to bring down the power grid—cyberterrorism. (For a scary video of what hackers can do to a generator, check out this declassified YouTube video from the Department of Homeland Security showing the Aurora Project.) There is even concern about “space weather” or coronal discharges from the sun that could cause widespread power outages.

This got us thinking on the Dummerston Energy Committee about preparing for such problems. What can a community like ours do to become more resilient?

Community Resilience

We realized that it would be useful to find out what percentage of Dummerston residents have emergency generators. How many have water supplies that can be accessed when there’s no power? What percentage of houses in the town can be heated with wood if there were either a shortage of heating fuel or an extended electricity outage that meant we couldn’t use our furnaces or boilers? How many renewable energy systems are there in town that can provide power when the utility grid is down? Are there places with emergency power where residents can charge cell phones during extended power outages?

Resilience is a significant focus this year of the Dummerston Energy Committee. We’re intrigued, for example, about establishing resilience hubs around town that would satisfy key needs in the event of emergencies. This is something my wife and I want to provide with the Leonard Farm property we’ve purchased in West Dummerston, and it plays a role in some of the decisions we’re making with the house and barn.

Our hope on the Energy Committee is that just by answering questions about these issues on our survey, residents will start thinking about resilience. This is a major focus of mine—especially since launching the nonprofit Resilient Design Institute in 2012—and I’m hopeful that by raising awareness about resilience, more Dummerston residents will incorporate various resilience strategies into their homes. Doing so will help our community weather future storms and power outages relatively easily.

Leonard Farm will include a modern, high-performance hand pump, such as this one made by Bison Pumps, that neighbors will be able to use during power outages.
Photo Credit: Alex Wilson

Ancillary benefits of resilience

Many of the strategies that can help a community become more resilient also help residents in other ways. If we improve the energy performance of our houses enough that they will never drop below 50°F at night during a power outage, as my wife and I are doing with the Leonard Farmhouse I’ve been writing about in this column, those houses will require very little energy during normal times for heating and cooling.

If we pay attention to efficiency in choosing our appliances and lighting so that key loads can be served with a back-up generator or islandable solar-electric systems, our electric bills will be kept low, saving us money and keeping our utility companies from having to invest in expensive new power plants.

If we use water resources more frugally and provide for rainwater harvesting, our lawns and landscapes will be more likely to be kept green in the event of a drought.

If we create communities in which we can get around in the event of a gasoline shortage—or an inability to pump gas (as occurred with Superstorm Sandy n New York and New Jersey last year)—these places will be more walkable and pedestrian friendly. In the process, we are finding, such communities provide a better quality of life and become more sought-after in today’s housing market, boosting property values.

These are win-win solutions, and our energy survey in Dummerston will help us identify strategies for boosting our resilience while saving residents money and delivering other ancillary benefits.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-08-14 n/a 17497 Beating the Achilles Heel of Grid-Tied Solar Electric Systems

A new inverter from SMA allows us to draw some daytime power from our PV system when the grid is down, even without batteries

The 18 kW PV array on our barn is a group-net-metered system with some of the output going to other houses. Click to enlarge.
Photo Credit: Alex Wilson

One of the biggest complaints I hear about most solar-electric (photovoltaic, PV) systems is that when the grid goes down you can’t use any of the power that’s produced. Consumers have spent thousands of dollars on a PV system, and during an extended power outage during a bright, sunny day when the PV modules are certainly generating electricity, they are disappointed that none of that electricity can be used.

This problem applies to net-metered PV systems that do not include battery back-up. Off-grid systems work just fine when the grid is down, but the vast majority of the roughly 300,000 PV systems in the U.S. are net-metered systems without batteries, and most of them lose all functionality when the grid is down.

Given my focus on resilient design (including my founding of the Resilient Design Institute last year), I wanted to install a solar-electric system at Leonard Farm that would have at least some functionality during power outages.

Full islanding capability

I wish we had full “islanding” capability with our PV system. Islanding refers to the ability for a PV system and the loads connected to it to be separated from the utility grid during outages so that no electricity could be fed into the grid and injure utility workers who are trying to repair down lines.

We have three inverters in our system that are housed in a downstairs room in the 1812 barn. The one with Secure Power Supply is the third from the right.
Photo Credit: Alex Wilson

Fully islandable PV systems require specialized inverters along with battery banks that allow them to function off-grid. The battery bank not only provides for functionality at night, but it also establishes the proper waveform during the daytime when the grid is down so that AC power can be delivered to the house.

Some islandable systems, such as the OutBack Radian and Schneider Electric’s Xantrex XW-series inverters, rely on a single inverter that can connect to the grid and a battery bank and switch back-and-forth automatically. Such inverters communicate with and draw electricity from the battery bank during a power outage and also send electricity into the grid during normal operation. These are sometimes referred to as bi-modal inverters.

There are other, battery inverters that can be added to a PV system that already has one or more PV inverters. Inverter manufacturer SMA offers such an option, the Sunny Island inverter that switches between the battery bank and SMA’s Sunny Boy grid-tie inverters with fully integrated controls. SMA’s approach is proprietary, in that the Sunny Island battery inverters only talk to Sunny Boy grid-tie inverters.

The MS-PAE inverters from Magnum Energy offer similar functionality, but can be integrated into systems with inverters from other manufacturers. There are various companies that package this type of inverter with a battery bank and the needed controls to provide islanding, or “AC-coupling” when the grid is down. MidNite Solar is one such packager of retrofit kits.

With any of these options for full islanding capability, there is a significant cost for this type of islanding capability. For a typical, residential-scale 6 kilowatt (kW) system, the cost ranges from about $8,000 to $16,000, according to Mark Cerasuolo of OutBack Power Technologies, who did an analysis of AC-coupling options. This cost includes the specialized inverter, battery bank, and necessary controls.

Detail of our Sunny Boy 5000TL-US inverter. The outlet beneath it provides emergency power during outages (when the sun is shining).
Photo Credit: Alex Wilson

A new, low-cost approach

As I said, we didn’t go with full islanding capability, even though I would have liked to do so—and may in the future. The cost of the battery system and other components was just too much for our budget that has been stretched pretty thin with our complex building project—which is finally nearing completion.

What we did do, however, was install a brand-new inverter from SMA that has an outlet that can continue delivering some electricity when the sun is shining during a power outage. SMA calls this feature “Secure Power Supply.” Mounted beneath our 5 kilowatt (kW) Sunny Boy 5000TL-US inverter is an outlet that can deliver 1,500 watts (12.5 amps at 120 volts) during the daytime the power grid is down. Unlike other islanding systems, there is no requirement for battery storage with this option.

This isn’t enough power to operate all the loads in our house that I’d like to power during a power outage, but it’s far better than nothing. The cost is essentially the same as a standard Sunny Boy inverter (though a separate outlet has to be installed). Ours was installed by Integrated Solar Applications in Brattleboro, which installed the  entire 18 kW net-metered system (with 6 kW being owned by a neighbor).

Like other models in the SMA TL line, our 5000TL-US is a transformerless inverter, which is smaller and lighter than standard inverters, and it offers even higher efficiency: roughly 97%.

Emergency power uses

While 1,500 watts is a significant amount of available power, this Secure Power Supply feature is not really intended for loads that have significant surges as they cycle on or that could be harmed by fluctuating current, such as refrigerators. It’s really designed for charging cell phones and laptop computers.

But I’ll be carefully examining power consumption and surge demand when we shop for a new chest freezer—it would be very nice to be able to power that freezer during the daytime during extended power outages.

Our PV array being installed on the structurally reinforced roof with standing-seam metal roofing.
Photo Credit: Alex Wilson

There may be a Sundanzer chest freezer, for example (a freezer made especially for solar systems that can work in DC or AC mode), that will work well with the limited output from our inverter. At the very least, we’ll be able to keep our cell phones and laptops charged and power our cable modem and router.

Still in limited supply

I had heard about the new 3000TL-US, 4000TL-US, and 5000TL-US inverters late last year, and heard that they would be shipping in the first half of 2013, but it turns out that we got one of the very first to be installed in the U.S.—or at least in the Northeast. Demand is very high for these systems.

I suspect that within a few years, most grid-tie inverters will include this emergency-power option. I haven’t had to test it out yet, but will be ready for that ice storm this coming winter!

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-08-07 n/a 17471 Smart Vapor Retarders: Not Just Your Grandmother’s Poly

New smart vapor retarders block most vapor diffusion when you want to eliminate risk of condensation, but allow vapor flow when you want drying potential

Our Pro Clima DB+ smart vapor retarder on the insulated roof. Click to enlarge.
Photo Credit: Alex Wilson

Nowhere in building design has there been more confusion or more dramatic change in recommended practice than with vapor retarders. Thirty years ago, we were told to always install a polyethylene (poly) vapor barrier on the warm side of the wall. Then we were told to forget the poly and go with an airtight layer of drywall (airtight drywall approach). Insulation contractors, meanwhile, often said to skip the vapor barrier; we need to let the wall or ceiling cavity dry out.

It made for a lot of confusion. And I’m not sure we’re totally out of the woods yet.

Some experts are now looking to vapor retarders whose vapor permeability changes based on the humidity conditions. We installed one of these new materials on our house.

Changing recommendations

Back when poly was the default choice as a vapor retarder (called vapor barriers back then), the recommended placement of that layer varied depending on where you lived. The rule was to install it on the “warm side.” In northern climates, that meant that the vapor retarder should be on the inside (installed on the inner face of wall studs and rafters) before installing drywall.

The idea was that we wanted to prevent water vapor from migrating from inside the house (where it was warmer) outward through the building envelope. As vapor-laden air cools off, it is able to hold less moisture, and if it gets cold enough the moisture in the air will condense (i.e., it reaches the dew point)—causing problems by wetting the insulation or rotting wood framing. By installing the vapor retarder on the inside of the wall, we would keep that water vapor out of the wall cavity where it might condense.

The DB+ was stapled to the rafters (really flanges of trusses) and the joints taped.
Photo Credit: Alex Wilson

In warmer climates, we were told to install the poly vapor retarder on the outside of the wall cavity, because the inside of the air-conditioned house was colder than the outside.  In this case the risk was that condensation could occur with moisture laden air moving inward through the building enclosure and cooling off.

But what about places where some of the time it’s warmer inside than outside and at other times it’s just the opposite: colder inside than outside. It turns out that this is the case in most of the U.S. Even in chilly Vermont, where I’m based, most new houses are now being built with air-conditioning—and after the heat wave this past July, I'm sure we'll only see more of it.

Confused? So is most of the building industry.

Smart vapor retarders

One solution to the changing conditions of a house during the annual cycle is to install a vapor retarder whose permeability (a measure of how readily water vapor can pass through) varies based on the humidity. These are often referred to as smart vapor retarders. The goal is low permeability in the winter when humidity is low but it’s critically important to block moisture flow and prevent condensation, and high permeability in the summer when humidity is higher and you want drying potential to both the interior and exterior

It turns out that the plain old kraft paper facing on fiberglass batts has this variable permeability property—as leading building science expert Terry Brennan explained to me. As humidity increases (in the summer), it becomes more permeable to moisture, while in winter, when the humidity drops, it becomes less permeable and a better vapor retarder. Terry describes it as “poor man’s vapor retarder.”

Strapping being installed for hanging drywall. Given the thickness of insulation, we opted to install strapping 12" on-center.
Photo Credit: Alex Wilson

About 15 years ago, researchers in Europe began working in a more focused way on variable-permeability vapor retarders. The first such product I heard about was MemBrain, made by CertainTeed’s parent company Saint-Gobain (headquartered in France) and available from CertainTeed in the U.S. MemBrain is a polyamide or nylon sheet with permeability that ranges from less than or equal to 1.0 perms in low humidity conditions to more than 10 perms under high-humidity conditions.

Two variable products are also made by Pro Clima in Germany and distributed by 475 High Performance Building Supply in Brooklyn, NY. Intello Plus is made from a polyethylene copolymer, and it varies in permeability from 0.17 in the winter to 13 in the summer. It comes in rolls 1.5 meters (59 – 1/16”) wide and 50 meters (164’) long.

DB+ is a less expensive, paper vapor retarder made by Pro Clima that varies in permeability from 0.8 perms with low humidity to 5.5 perms at high humidity. It is made mostly from recycled paper, and includes a fiberglass reinforcement grid. It comes in rolls 1.35 meters (53”) wide by 50 meters (164’) long. It is about 24% less expensive than Intello Plus.

Calculating moisture risk

There’s a software tool called WUFI that can be used to determine what the moisture dynamics are likely to be in a particular building assembly and climate. In our project, we were concerned about our roof assembly, because the sheathing was outside of the vented roof cavity. We worried that there might not be an adequate air barrier in the roof assembly.

Terry Brennan used WUFI to determine that as long as there is at least minimal roof ventilation we would be fine without a vapor retarder on the interior. But our roof dormers weren’t going to be vented and the main roof wouldn’t be vented above the roof valleys. So we decided to install a vapor retarder as an insurance policy.

To allow drying to either the interior or exterior, we decided to go with a variable-permeability product, and we opted for Pro Clima DB+. The performance isn’t quite as good as Pro Clima’s Intello Plus, but the cost was lower and DB+ had some environmental attributes—such as being made from 50% recycled paper and being recyclable.

This is one of the dormers, where we don't have roof ventilation.
Photo Credit: Alex Wilson


Installation of the DB+ was pretty straightforward. It went up after the Spider insulation had been installed. It was held taught over the rafters and stapled in place. Following installation for several days there was a reasonably strong ammonia smell. Ken Levenson of 475 looked into this and found out for me that it is from the ammonium phosphate that is added as a flame retardant. By the time strapping and drywall went up, the smell was gone.

We didn’t bother with the vapor retarder on the walls, because there we have a well-sealed air barrier in the middle of the wall—made from Zip sheathing with edges taped and extra air sealing using the EcoSeal product from Knauf.

We’re happy. The drywall is now mostly installed, and we look forward to never having to worry about moisture accumulating in our insulation. At least until the next theory of moisture control comes along….

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-07-31 n/a 17423 Getting to Know Spider Insulation

Spray-applied fiberglass insulation offers huge benefits over fiberglass batts and even has some advantages over cellulose

Spider insulation being sprayed into an open wall cavity. Click to enlarge.
Photo Credit: Alex Wilson

We’ve just completed the installation of a relatively new and (at least in New England) little-known insulation material called Spider. As a reminder, the house we are renovating (really re-building) in Dummerston, Vermont has provided an opportunity to try out dozens of innovative products and materials that I’ve long researched and written about in Environmental Building News.

Insulation has been a particular focus of the project, in part because some of the most common insulation materials on the market have environmental or health concerns, including halogenated flame retardants and blowing agents that contribute significantly to global warming.

In previous blogs I described Foamglas, a cellular-glass material, that we installed under the foundation slab and on the outside of the foundation walls, and expanded-cork boardstock insulation that we installed on the outside of above-grade walls spanning over the wood framing. Here I’m covering the third innovative insulation product we used on the project: a spray-applied fiberglass product made by the Johns Manville Company called Spider.

Spray-applied insulation that doesn’t require netting

Spider insulation is installed into open wall and ceiling cavities in much the same way that damp-spray (or wet-spray) cellulose is installed. Like cellulose, it fills very well around wires, penetrations, and any irregularities in the wall cavity—it performs far better than fiberglass batts, which I think should only be considered on very small jobs where bringing in an insulation contractor can’t be justified.

The spray nozzle coats the fibers with an acrylic binder as they exit the nozzle.
Photo Credit: Alex Wilson

The fiber insulation is sprayed from the truck and as it is blown into the wall or ceiling cavity the fibers are coated with a small amount of acrylic binder. That makes the fibers sticky (thus the name “Spider”) so they stay in the cavities. It even works in overhead cavities, where netting is required with cellulose.

As with damp-spray cellulose, the cavities are over-filled, then the excess is trimmed flush with the inner face of the studs or rafters. This is done with a special “scrubbing” or “screeding” tool, which has a wide, electric roller that spans two studs or rafters.

As Spider is installed, a second worker vacuums up the material that doesn’t stick to the cavity or is scrubbed off, and this goes back into a hopper in the truck. With the most advanced installation equipment, as was used on our project by Environmental Foam of Vermont, the recovered insulation is mixed with virgin material at a ratio that can be adjusted. For overhead blowing into cathedral ceilings, a higher proportion of virgin insulation is recommended for better adherence, while a higher proportion of the recovered insulation can be used in walls.

Because the fibers pack tightly and install at relatively low density, a lot of insulation can be loaded into a truck.
Photo Credit: Alex Wilson

Comparisons with cellulose

I have long been a fan of cellulose insulation, and I have actively promoted it over the years. But spray-applied fiberglass has some advantages that I came to appreciate while working with and chatting with the installers.

While cellulose has higher recycled content (about 80%—the rest being flame retardant, usually borates), Spider has reasonable recycled content: 20% post-consumer and 5% pre-consumer recycled glass.

Spider goes in at significantly lower density: typically 1.8 pounds per cubic foot (pcf), while cellulose is typically installed at 3.5 to 4.0 pcf. For our cathedral ceiling application, we were worried that the 15” insulation depth would be so heavy with cellulose that it would cause the drywall to bow inward between the strapping.

The insulating value is slightly higher with Spider: R-4.2 vs. 3.7 to 3.8 for dense-pack or damp-spray cellulose.

As fiberglass is sprayed into the wall or ceiling cavity through a 4" hose, excess is vacuumed up and returned to the truck through a 6" hose..
Photo Credit: Alex Wilson

Acoustic performance is similar; both work very well at blocking noise. According to Johns Manville, Spider installed in a 2x4 exterior wall, with 1/2” particleboard siding, 1/8” pressed-cardboard sheathing, and 1/2” drywall, provides an STC (sound transmission class) rating of 43, which is much higher than a comparable wall with fiberglass batt insulation and somewhat higher than a wall with cellulose.

Fiberglass is an inorganic fiber, so if it gets wet it may dry out better than cellulose—though you don’t want any fiber insulation material to get wet.

From a health standpoint, cellulose and Spider are both made without formaldehyde, but Spider doesn’t require a flame retardant, while cellulose does. While the borate flame retardants used in cellulose have always been considered safe for humans, the Europeans have recently challenged that contention, and those chemicals are being considered for addition to the European REACH program. There has in the past been concern about respirable glass fibers potentially being carcinogenic, but this concern has largely disappeared, and with Spider few fibers seem become airborne.

Spider installation is far less dusty than cellulose. I was working in the house during most of the two-day installation, and I was amazed how little insulation was in the air. I wore a dust mask, but was otherwise unprotected. My arms and eyes didn’t get at all itchy, as they do when I have installed fiberglass batts. The installers were wearing shorts and tell me that they experience no itchiness.

A special "scrubbing" tool trims the insulation even with the inner face of studs and rafters.
Photo Credit: Alex Wilson

For our installer, Kent Burgess of Burlington-based Environmental Foam of Vermont (an insulation contractor who installs a wide variety of insulation materials, despite the name), one of the biggest advantages over cellulose is that he can fit about two-and-a-half times as much of the bagged material into his truck than with cellulose. This is mostly  because it goes in at a lower density, but I think the packed bags are also more dense. For a large job this can mean avoiding the need to return to home base to fill up with bags of material.

Kent used to install a lot of cellulose, but he far prefers Spider now. He is fairly new to Spider—having purchased equipment only last fall—so he was able to convince his mentor, Kyle Novak, of Advanced Insulation Systems in Travers City, Michigan to make the 12-hour drive east to help out of our job. The deep, sloped-ceiling application was tricky, and Kyle’s experience would be invaluable, since he has been installing Spider since early 2006, not long after it was introduced to the market.

Cost and performance

Kent says that Spider averages about 10% more expensive than damp-spray cellulose, but costs have a lot to do with the size of the project and the distance traveled. For a project further from his home base, using Spider can avoid the need for a return trip to pick up more material. In that case, Spider will be significantly less expensive.

Kent says the price of installed Spider averages about $1.50 to $1.65 per square foot for a 2x6 wall, or roughly 28-30¢ per board-foot, vs. maybe 24¢ per board-foot for cellulose. A quality closed-cell spray polyurethane foam (SPF) job will cost 80¢ to $1.00 per board foot for a large job, and with SPF there is the issue of how much can be installed at a time (because the curing is an exothermic reaction, and the foam heats up). Plus, Spider is a lot safer; supplied-air respirators aren’t needed with Spider, while they are with SPF.

After trimming the insulation and cleaning up, the job looks great. A variable-permeability vapor retarder will be added on the insulated ceiling--thus the prep at the closet partition.
Photo Credit: Alex Wilson

The drawback is the cost of getting set up to install Spider. Kent has about $70,000 invested in the equipment.

In the seven years Kyle has been installing Spider he’s had no real problems. “I think it’s the greatest thing on the face of the Earth,” Kyle told me after spending a day-and-a-half spraying the material. “It doesn’t settle,” he said, and customers love the look of the finished job.

When Kyle has gone back into houses insulated with Spider to do repairs or additions and opened up walls, he has seen absolutely no problems.

For cavity-insulation applications, Spider is a great option. Cellulose is also a great product, but for deep installations and sloped ceilings, I don’t think anything beats Spider today. Fiberglass batts aren’t even in contention.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-07-22 n/a 17415 Choosing Insulation Levels Based on Your PV Costs

Some suggest that we should base decisions about insulation levels on the cost of supplying the necessary heating or cooling with solar electricity

Photovoltaic (PV) system being installed on our barn roof.
Photo Credit: Alex Wilson

There’s an age-old question of how much insulation to install in our homes. In the green building community, there is a contingent that says to add more until the “payback” for the added insulation isn’t worth it—until the energy savings that will result from the insulation doesn’t pay back the cost of that insulation quickly enough.

Energy and environmental consultant Andy Shapiro, of Energy Balance, Inc. in Montpelier, suggests a different approach: basing that decision on the cost of solar.

Energy conservation and the cost of solar.

Andy argues that once we get to very high levels of insulation, it doesn’t make sense to spend more on energy conservation than it would cost to supply that saved heat (or cooling) with a photovoltaic (PV) system used in an air-source heat pump. Air-source heat pumps (often referred to as mini-splits—see "7 Tips to Get More From Mini-Splits") are the heating and cooling system of choice today for many highly efficient homes; they offer two to three times the efficiency of standard baseboard-electric heating systems. Using PV as the benchmark makes sense, because—like conservation—after the up-front investment, there is little to no operating cost.

To illustrate this point, Andy evaluated a 1,000 square-foot roof insulated to either R-60 or R-80. In the 7,700 degree-day climate of Burlington, Vermont, the R-60 roof results in a heat load of 390 kilowatt-hours per year (kWh/yr) or 3.1 million Btus per year (MMBtu/yr), or vs. 290 kWh/yr or 2.3 MMBtu for the R-80 roof. In this analysis I’ll mostly use kilowatt-hours (kWh) as the measure of both thermal and electrical energy, as is common in most of the world; Btus (British Thermal Units) are unique to the U.S.

The savings from providing the extra R-20 in the ceiling is 98 kWh/yr. Andy assumed that the cost of the PV system is $4 per peak-watt ($4,000/kWh-peak) without any tax credits or other incentives, and he assumed that a PV system in Burlington’s relatively cloudy climate will generate 1,100 kWh/yr for every peak kW of rated capacity, while the air-source heat pump has an assumed coefficient of performance (COP) of 2.3.

Given these assumptions—which are certainly up for debate—providing 98 kWh/yr of heat will require 0.089 rated kW of a PV system (98 ÷ 1,100). At $4 per installed peak-watt, the cost of that PV system would be $356, or $0.36/ft2 of roof. With this analysis, adding the extra R-20 to the roof will make sense as long as it costs less than $357. In reality, such a change would cost more like $750, or $0.75/ft2 (assuming loose-fill cellulose and just the cost of the insulation). In other words, it makes better economic sense, in this example with these assumptions, to stick with the lower R-value (R-60) and invest in the PV capacity.

We used a combination of cork insulation and spray-applied fiberglass to achieve about R-45 in our walls and about R-60 in our roof.
Photo Credit: Alex Wilson

Using investment in PV as a benchmark for conservation investments

I like this approach for figuring out how much we should spend on energy conservation. It could be used not only to evaluate investments in insulation, but also investments in air tightness and some pieces of equipment, such as a heat-recovery ventilators (HRVs). Andy’s calculations assume no tax credits, rebates, or other incentives for PV; with such incentives in place (as is currently the case), the argument is even stronger.

One thing the analysis does not account for is the fact that investments in insulation should continue paying off for a very long time (maybe even a few hundred years if the house is well-built and the insulation protected from damage), while a PV system will need to be repaired and periodically replaced during the life of the insulation. This analysis does not address lifetime costs of PV and insulation; doing so would require an assumption regarding the discount rate and an estimate of future maintenance costs.

My friend Dave Timmons, Ph.D., who is working on models of renewable energy economics and who teaches ecological economics at the University of Massachusetts, notes that for electricity there is a formula for the levelized cost of energy (LCOE), and he suggests that one could develop an analogous calculation for the levelized cost of conservation, so that we’re comparing apples to apples. (But I’ll have to leave that to the economists who are a lot smarter than me.)

Dave also points out that the analysis doesn’t account for the cost of electricity storage. Producers of PV electricity today are able to use the grid as a storage system, but that may change as renewables begin accounting for a larger percentage of electricity production. Viable storage in the grid may increase the assumption we should use for PV cost.

What about with lower insulation levels?

I’ve used this argument for deciding between really high levels of insulation: R-60 vs. R-80. How does it work when applied to insulation levels most builders are using?

If we are considering boosting attic R-values from R-19 to R-38 (also an increase of about R-20)—the economic argument for investing in conservation is far different. In this case, the savings in heat would be 620 kWh/year to go with the additional insulation and the cost of PV needed to deliver this heat would be $2,250, or $2.25/ft2. Clearly, the extra insulation, at $750 ($0.75/ft2), is a better investment.

This second example illustrates the argument I’ve long made that it makes sense to invest in energy conservation first and only after that put in the PV system. But if you go far enough with conservation, as Andy argues, you eventually reach a point where it doesn’t make economic sense to invest in he additional insulation.

Does this reasoning make sense? I’d be interested in your thoughts.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-07-10 n/a 17319 From Tyvek to Pro Clima: The Evolution of Weather-Resistive Barriers

We’ve come a long way from the early Tyvek housewrap; our experience with the German Pro Clima Solitex weather-resistive barrier

Pro Clima Solitex weather-resistive barrier installed on our home. Click to enlarge.
Photo Credit: Alex Wilson

I remember years ago—I hate to remember how many; it must have been around 1982 or 1983—writing for New England Builder (now the Journal of Light Construction) about Tyvek housewrap. It was then a fairly new product—and really a new idea: a material that would wrap over the outside of a house to provide an air barrier and improve energy performance.  

Tyvek wasn’t actually new in the early 1980s—it was invented by DuPont in 1955 and first commercialized in 1967—but it was new enough in the building industry that two technical experts from DuPont trekked up to Vermont to give me a dog-and-pony show about it. New England Builder was gaining a reputation as a leading purveyor of practical, on-the-ground information for builders, and DuPont wanted to get the message out.

I used Tyvek houswrap on our 1788 house, which I was then in the process of renovating. I had removed the old shingle siding, repaired some rotted sills, replaced some sections of board sheathing, insulated on the interior with fiberglass between the studs (plus an inch of extruded polystyrene on the interior of the studs), and I wanted to provide a reasonable air barrier on the exterior.

Tyvek after 30 years.
Photo Credit: Alex Wilson

Tyvek seemed like the way to go. It is a spun-bonded polyolefin (polyolefins are polymers, usually either polyethylene or polypropylene, made up of long chains of carbon and hydrogen) that comes in a roll wide enough to provide a continuous layer on the outside of the house. It seemed ideal.

Thirty years later, doing some repairs to drainage around the house I had opportunity to remove some of that Tyvek, and I was struck by how much it had deteriorated. It turns out that Tyvek—at least the formula that was being used thirty years ago—was significantly damaged by surfactants in wood siding. (I didn’t know enough then to provide a rainscreen detail using strapping, which would have separated the wood siding from the Tyvek and improved the housewrap’s durability.) The material almost disintegrated in our fingers as we examined it.

Evolution of weather-resistive barriers

We installed Solitex Mento 1000 over 6" of expanded-cork exterior insulation, taping it to the pre-wrapped window surrounds.
Photo Credit: Alex Wilson

A lot has happened with housewraps in the 30 years since DuPont paid me that visit. I was just on the DuPont website, and the first thing I noticed was that there are now nearly a dozen types of Tyvek: the standard HomeWrap, StuccoWrap, a roof product, a handful of commercial products, Tyvek tapes to seal one layer to another, plus all the non-building-related products for mailing envelopes, protective haz-mat suits, etc.

Following DuPont’s success in creating a new type of product, there were lots of entrants into the housewrap industry: Typar (cleverly named to confuse the user into thinking it was Tyvek?), various perforated polyethylene films, and some textured products that try to achieve a sort-of rainscreen (air space behind the siding).

In fact, in the building-science community the good-old housewrap has evolved into the weather-resistive barrier. It’s either an attempt to impress clients with a far-more-impressive-sounding product that justifies the cost, or perhaps an effort to mirror the dry terminology found in building codes. These barriers are supposed to keep out rain and wind (air flow), yet they need to be permeable enough that any moisture that finds its way into the building enclosure can evaporate and escape to the exterior.

For more on WRBs, see Choosing the Best Housewrap: A New Standard for Weather Barriers.

Enter the Europeans

So what did I use on our current house project? We ended up going with a German weather-resistive barrier (WRB) called Solitex Mento 1000, made by Pro Clima and distributed in the U.S. by 475 High Performance Building Supply in Brooklyn, New York. (475 is a specialized building material supplier serving low-energy and Passive House construction.)

Strapping installed over the WRB.
Photo Credit: Alex Wilson

Solitex is one of a number of European WRBs that go beyond typical American products in their performance. The other that I’m somewhat familiar with is SIGA Majvest Exterior Wall Membrane, a Swiss WRB distributed in the U.S. by Small Planet Workshop in Olympia, Washington.

Solitex Mento 1000 is a high-performance WRB that offers both very good water penetration resistance and very high water-vapor permeability. According to the company and 475, the product resists a 33-foot water column even as it provides 38 perms excellent numbers in both cases. 

Meanwhile, it goes a long way toward restricting air flow through the wall or roof assembly, with air permeance of 0.00004 cubic feet per minute (cfm) per square foot, according to standardized test methods (ASTM E2178).

Technically, Solitex Mento 1000 is a three-layer monolithic TEEE film (Thermoplastic Elastomer Ether Ester) with polypropylene protective layers. By being monolithic, it has no pores, so it is more weather-resistant than standard housewraps, while actively transporting vapor outward during the heating season. This means that the TEEE functions at lower pressure differential between inside and outside, than the more common microproous/woven products.

“With traditional housewraps,” explains Ken Levenson of 475, “the vapor permeance is from the microscopic tears in the woven membrane, which the vapor can push through,  while with the monolithic membrane with no tears or pores, it is the actual molecular structure that is transporting the vapor.” As such, because traditional wraps resist vapor diffusion at lower pressures, there is greater chance of moisture build-up filling the pores which can block vapor movement, while the molecular structure of the monolithic membrane moves the vapor at very low vapor pressure differentials, avoiding the danger of blockage.

Also, the membrane’s performance will not degrade from surfactants in cedar siding, according to Levenson.

Installing Pro Clima Solitex Plus WRB to form the vent space under the roof sheathing. The WRB is caulked and stapled to the top chords of the rafters.
Photo Credit: Alex Wilson

It is recommended for exterior walls and roofs. With roofs, it can even serve as a temporary roofing layer until roofing is installed. In our roof system, we used a slightly different version, Solitex Mento Plus (with a reinforcing grid), as a layer to achieve the air space under the roof sheathing. The WRB provides both a waterproof layer to shed any water that may get into the air space and an air barrier in the insulated roof system.

Cutting sections of Solitex Mento Plus for between the rafters in forming the air space above the insulation; the WRB will protect the insulaton from any moisture that gets in, while allowing the insulation to dry out if it does get wet.
Photo Credit: Alex Wilson

Pro Clima Solitex comes in 1.5-meter (59”) rolls that are 50 m (164’) long. Edges and overlaps are sealed with Pro Clima Tescon tapes.

Compared with the very lightweight, nine-foot-wide rolls of Tyvek, the installation may be more time-consuming, but I am confident that we have a weather barrier that will do a superb job of protecting our house, while helping achieve the airtight construction we are seeking and allowing any moisture in the wall cavities to escape.

I’m hoping this WRB will still be doing its job in 75 to 100 years, when it will be time to replace the siding on the home.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-06-25 n/a 17309 Should We Expect Energy Modeling to Predict Building Performance?

On this Department of Veterans Affairs Omaha VA Medical Center, energy modeling was used from the outset to analyze nine different massing schemes down to three more schematic schemes, then throughout the design of the selected scheme to optimize building massing, mechanical systems, daylighting, and onsite renewable energy usage.

The green building industry focuses far too much on energy modeling to predict performance, not to make early design decisions.

Let me put my headline question another way: Is prediction of building performance the highest use of energy modeling during building design?

This question came to mind after I sent an email to our members this morning about our upcoming (July 9th) webcast on Energy Modeling for Early Design Decisions. One individual responded to me and questioned the credentials of the panel of experts we assembled for this roundtable discussion.

He wrote: “Until you have an energy model that is a good prediction of the way a building operates and the amount of energy used (and is verified by a independent 3rd party) then one needs to be wary” about claims of expertise in modeling.

There is a lot of value in an energy model that reflects the building “as built”: validating LEED points, validating code compliance, and setting the stage for measurement and verification.

But, as I wrote recently in the EBN article, Energy Modeling: Early and Often, “after the massing, orientation, envelope and glazing design, and mechanical systems in a building are already specified, and hundreds of hours of work have already been put into those designs—the modeling might have little value beyond keeping score.” With a quote from Marcus Sheffer, who will be on our webcast panel (and who  wrote the book on energy modeling in an integrative design process), I went on to say:

“It blows me away that that’s where we are,” says Marcus Sheffer, an energy consultant with 7group. As critics have pointed out, a 'green' building modeled to save a certain amount of energy doesn’t necessarily end up doing that. Given accurate inputs, models are accurate at forecasting energy use, says Sheffer, but “models can’t accurately predict the future”: actual operating conditions will always differ from modeled conditions. This typically happens because equipment and controls are installed differently than modeled, or because weather patterns or occupancy are different than expected. The real value of modeling is not predicting energy use but making relative comparisons among design options, says Sheffer.

I agree with Sheffer. There is way too much focus put into the energy model and how predictive it is of performance, and not enough put on iterative modeling during early design to choose between designs A, B, C, D, and so on.

Our most stringent energy codes and prescriptive guidelines today get us no more than 40% savings over common practice.  What we need are 50%, 60%, and greater savings, and we need early modeling to get there.

Do you agree? Disagree? Why? I hope you’ll join me and Marcus Sheffer, Troy Hoggard, Amanda Bogner, and Prasad Vaidya for a lively discucssion at our July 9th, 1:30 p.m. ET webcast on Energy Modeling for Early Design Decisions. It’s free to sign up.

2013-06-20 n/a 17296 Icebox or Oven? What Happens to Interior Temperatures When the Power Goes Out


If buildings lose power or heating fuel, how hot is too hot and how cold is too cold?

An elderly woman in New York City trying to keep cool without air conditioning—though with an electric fan.
Photo Credit: David Goodman - from the Buildings Resiliency Task Force Report

Over the past five months, the New York City Buildings Resiliency Task Force has been working to figure out how to make buildings in the City more resilient. The Task Force, which was created at the request of Mayor Michael Bloomberg and City Council Speaker Christine Quinn in the wake of Superstorm Sandy and facilitated by Urban Green, the U.S. Green Building Council Chapter in New York City, issued its recommendations on June 13, 2013.

The Task Force included about 200 people organized into four building-type committees (Commercial Buildings, Multi-family Residential Buildings, Critical Buildings, and 1-, 2- and 3-Family Homes and three Working Groups (Structure, Façade, and Interiors; Electrical and IT; along with HVACR, Plumbing and Fire Protection). I participated in several meetings as an at-large member of the Task Force

The findings were presented in a 40-page Summary Report as well as a much longer, 185-page document that includes detail on each of the 33 proposals being presented to the City. It is important to note that these are advisory recommendations only; there is no guarantee that any will be acted on.

The report includes fives types of recommendations based on suggested implementation: Required Actions, which would be mandated as retrofits for existing buildings (there are very few of these); New Code measures that would be incorporated into codes for new buildings and major remodeling projects; measures that would Remove Barriers to creating more resilient buildings; Recommended Practices; and measures that require Further Action.

These 33 proposals range from providing access to potable water in multifamily residential buildings at a level in the buildings where municipal pressure will deliver the water (so that residents on upper floors will have access if pumps in the building are inoperable), preventing sewage backflow into basements (a huge problem with Sandy), ensuring operability of toilets and sinks during power failures; eliminating existing barriers to elevating buildings above flood levels, capturing stormwater to reduce flooding, providing quick connections to temporary (mobile) generators and boilers, and requiring operable windows.

Find the superinsulated row house in this Brooklyn streetscape. This thermographic image shows very little heat loss from one house, which will maintain habitable temperatures during a long-term power outage. Click to enlarge.
Photo Credit: Sam McAfee, - from the Buildings Resiliency Task Force Report

Maintaining habitable interior conditions in the event of lost power

The measure that I’m most excited about in the Task Force report is a proposal to Maintain Habitable Temperatures Without Power. This has been a key tenant of the “resilient design” agenda I’ve been advancing through the Resilient Design Institute (RDI) and the concept of “passive survivability” that I’ve been pushing for since late 2005, following Hurricane Katrina in the Gulf Coast.

When power was lost in parts of New York City—in some places for several weeks—there was recognition by the City that conditions could get pretty dire very quickly, especially in high-rise residential buildings during hot weather (projected to become a more common occurrence). In the summer, temperatures may rise quickly to dangerous levels, and in the winter, temperatures will fall. We can refer to these as drift temperatures.

This is a big issue in New York City, which houses a remarkable 11% of the nation’s occupants of high-rise apartment buildings. There is clear recognition that evacuating millions of residents due to a weather event—or something else—that knocks out power for an extended period of time. With a population of 8.3 million, there simply isn’t a way to carry out a widespread evacuation; there has to be a way for residents to shelter in place.

What defines habitable temperatures

This brings me to one of the early focus areas of RDI: defining what constitutes habitable or livable conditions. In May of this year, RDI sponsored an all-day retreat of leading energy engineers, architects, planners, and public health experts to brainstorm metrics of resilience, including temperature and humidity. In follow-up to this Benchmarking Resilience retreat, a meeting participant and colleague, Seth Holmes, AIA, of the University of Hartford, will be taking the lead with a more in-depth literature review and expert interviews. We are hoping to produce a peer-reviewed technical paper on these issues in the fall.

Our first take at defining habitable temperatures (°F) in buildings that lose power or heating fuel. Click to enlarge.
Image: Resilient Design Institute

There are a lot of factors that come into play with the question of habitable conditions, including humidity (with higher humidity, moisture doesn’t evaporate as easily from our skin and we suffer more from the heat), duration (putting up with no air conditioning for one day is one thing, putting up with it for a week or two is very different), and perhaps regional adaptation.

Before the availability of air-conditioning, it was a pretty reasonable assumption that people in the south could deal with heat better than us northerners, but that may not be the case as much today. In fact, some suggest that those of us up north may now be better adapted to hot, humid weather than our southern neighbors, because we aren’t always in air-conditioned spaces. My guess is that we’ll end up with something like 90°F, with some correction for relative humidity as a reasonable upper boundary for habitability (see matrix).

At the low end of the livable temperature range, perhaps the argument for regional adaptation is stronger. My sense is that 50°F–55°F is a reasonable lower boundary for livable conditions—perhaps 50°F for more northern climates and 55°F for southern locations, where the blood is thinner.

This matrix is just a starting point. I would welcome input and references to technical publications that define habitable temperatures. Are these temperatures reasonable?

Buildings that maintain habitable conditions

Once we determine what a reasonable temperature range is for habitability—not comfort, mind you, but survivability—we can figure out what building design measures are needed to achieve those drift temperatures. And we should be able to model that performance using fairly standard energy modeling software.

Really well-insulated buildings will maintain the habitable conditions much longer than conventional buildings—perhaps even indefinitely. A home built to Passive House standards (a rating system for ultra-low-energy buildings that emerged in Germany and is gaining popularity here) incorporates not only very high insulation levels, super-high-performance windows, and very low air leakage, but also some passive solar gain.

In most places, such a home will never drop below 55°F or perhaps even 60°F in winter, even with no supplemental heat. And in the summer if such a house is wisely operated (closing windows during the day, for example), it should maintain temperatures significantly cooler than outdoors.

Moving ahead with this work

The Buildings Resiliency Task Force in New York City listed the proposal on maintaining habitable temperatures during power outages as a measure needing further action. Urban Green is hoping that the work of the Task Force can be continued into the fall to provide more detailed guidance on this and a number of other proposals.

If that extension is approved, I’m hoping that RDI will be able to provide detailed guidance, both on the metrics and on achieving such performance in buildings. We are still seeking foundation grants to support this work—so let me know if you have suggestions of foundations, corporations, or agencies that might want to support this work.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-06-18 n/a 17274 Installing A Group Net-Metered Solar Array

The 18-kW photovoltaic array on our barn roof is nearing completion

The first PV panels being installed on our barn roof. Click to enlarge.
Photo Credit: Alex Wilson

When we started planning the rebuild of our house and the rest of the farm in West Dummerston, Vermont my wife and I knew that we wanted to produce all of our energy onsite. That meant a solar photovoltaic (PV) system that would generate as much electricity as the house and barn are consuming—net-zero energy.

We also wanted to protect as much of the ten acres of agricultural land as possible. That meant we wanted to avoid a ground-mounted PV system. Wherever land can be used for farming—now or in the future—I prefer to install PV arrays on buildings, keeping the land open for agricultural uses.

Fortunately, the 1812 barn has a long roof facing almost due south. That would be the perfect location for the solar array. Our builder, Eli Gould, spent several months restoring the barn, which involved replacing damaged posts, adding sturdy granite supports under those posts, rebuilding several dry-stone walls to support the barn sills, lowering and leveling the floor, replacing some timber framing elements (including about a dozen round-log joists that we cut on the land), and reinforcing the roof to hold the solar modules.

After stripping the old roofing and repairing the original sheathing, a new layer of roof framing and roof sheathing was added.
Photo Credit: Alex Wilson

To maximize durability, we wanted the roof to be sturdy and not flex with wind or snow loads, so after stripping the layers of metal and asphalt roofing, we added a layer of 2x6 and 2x4 framing to the roof structure, flattening the roof plane at the same time. Zip sheathing went on over that, and then the roofing.

Standing-seam metal roofing

One of our goals for the whole project has been to maximize durability, so we spent quite a while debating different roofing materials. We wanted the solar panels to be able to attach to the roof without any penetrations, so that meant standing-seam metal roofing. S-5 brackets for the solar array tracks clamp on to the raised seams of the roofing with absolutely no penetrations of the roof. If panels have to be removed down-the-road for some reason, that’s relatively easy to do.

For the roofing itself, we chose 24-gauge Englert galvalume 1301 roofing with the company’s low-gloss Ultra Cool coating. According to James Hazen of the company, Englert’s paint line is one of the cleanest operations of its kind in the world, with 100% of solvent fumes from painting, drying and curing operations captured. The captured paint fumes are burned with all the recovered heat used in manufacturing. The company expects a 150-year life for the roofing. Roofing contractor Travis Slade, of River Valley Roofing in Putney, Vermont, has done an incredible job installing the standing seam roofing.

Standing-seam roofing nearly completed on the south roof.
Photo Credit: Alex Wilson

Group net-metered system

We have a great location that can hold an 18-kilowatt (kW) PV array, but we don’t need a system that large. So last fall we began investigating community solar options, and we found a neighbor who wanted to buy 6 kW out of the 18 kW system. In other words, this neighbor will actually own a third of the PV system that’s on our barn roof.

This option for someone else to own part of a PV system in a different place is referred to as group net metering, and Vermont is one of the few places where this can be done. Green Mountain Power bends over backwards to facilitate such systems, which is wonderful. Through this option, someone without a south-facing roof where PV modules can be installed can look elsewhere for a good south exposure.

Because the 12-kW system that we will own is still larger than we will need for our house and barn (at least until our farm needs expand), we will plan to sell our excess capacity to another Green Mountain Power customer.

S-5 clips clamp onto the standing seams of the roof to avoid penetrations.
Photo Credit: Alex Wilson

Selection of the PV modules

At the recommendation of our solar installer, Integrated Solar Applications, in Brattleboro, we are installing highly rated REC 250PE modules. The modules are rated at 250 watts, have 15.1% module efficiency, and come with a 10-year product warranty and 25-year “linear power output warranty” (guaranteeing that the degradation of power output will not exceed a 0.7% per year). REC is a Norwegian company with the silicon raw materials produced in the U.S. and silicon wafer, PV cell, and PV module manufacturing being done in Singapore.

Poor reliability and early failure of PV modules has been in the news lately, so I’m relieved that ours aren’t simply commodity Chinese-made modules (though some Chinese products are no-doubt fine).

Panels secured to the mounted tracks.
Photo Credit: Alex Wilson

In future columns I will address other features of our PV system, including “islanding” capability that will provide us with some electricity even when the electric grid is down.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-06-12 n/a 17233 Brattleboro's Slow Living Summit

This week’s Slow Living Summit celebrates local food, local economies, sustainability, and resilience.

The Slow Living Summit is happening June 5-7 in Brattleboro.
Image Credit: Strolling of the Heifers

For the past three years the Slow Living Summit has been an important ancillary event to the Strolling of the Heifers parade in Brattleboro, Vermont, which is now one of the state’s leading tourist attractions. With a nod to Spain’s famous Running of the Bulls, the Strolling of the Heifers is a relaxed walk along Main Street that focuses attention on farmers and local food.

Right from day one Strolling organizer Orly Munzing worked to provide an educational component to the event. So it was a logical extension to host a focused conference that tied into the Strolling.

But the Slow Living Summit, whose program committee I’ve participated in these three years, goes beyond food and agriculture.

Celebrating the idea of slowing down

The Slow Living Summit was inspired by the Slow Food movement in Europe—an effort to counter “fast food,” which is continuing to grow in dominance (approximately 19% of our meals are consumed in cars, according to Michael Pollan)—and the Slow Money movement, which is focused on local economies, local investing, and slowing down the pace and scale of the world of banking and finance. “Slow living” seeks to tie these together.

From the Slow Living Summit website:

’Slow’ encompasses several layers of meaning that go beyond simply ‘sustainable.’ Slow is the opposite of ‘fast’ — fast food, fast money, fast living—and all of the negative consequences ‘fast’ has had for the environment and for the health of people and societies. ‘Slow’ embodies cooperation, respect, sustainability, gratitude and resilience.

Strolling up Main Street during the 2003 Strolling of the Heifers, which follows the Slow Living Summit.
Photo Credit: Alex Wilson

Conference this Wednesday through Friday

The Slow Living Summit in Brattleboro begins Wednesday evening with registration, exhibits and networking in the Latchis Hotel lobby, a reception at 5:00 at the Latchis main theater, and the opening plenary beginning there at 6:30 pm. Speakers in the opening plenary will be Jonathan Lash, the president of Hampshire College and past president of the World Resources Institute, and Robert Repetto, a senior fellow at the World Resources Institute. There will also be remembrances of two local advocates of slow living, who passed away within the past year: Helen Daly and Keith Maillard.

Other plenary sessions during the conference include:

Thursday morning 8:30 to 10:00 - “Agriculture, Food, and Food Systems: Reconnecting Farmers, Eaters, and Healthy Communities” with Frances Moore Lappé, author of Diet for a Small Planet, and Judy Wicks, author of Good Morning, Beautiful Business: The Unexpected Journey of an Activist Entrepreneur and Local-Economy Pioneer. Wicks is also founder of the White Dog Café, Philadelphia, and a co-founder of Business Alliance for Local Living Economies (BALLE).

Thursday afternoon 1:45 – 3:15 – “Slow Design: The impact of mindful design on the quality of public spaces and their communities” with Jonathan Fogelson of the Michael Singer Studio; Roseanne Haggerty, president of Community Solutions in New York City; and Rasmia Kirmany-Fry, director of the Brownsville Partnership, a program of Community Solutions.

A session at last year's Slow Living Summit.
Photo Credit: Jesse Baker

Friday morning, 8:30 – 10:00 – “Transitioning to a New Economy,” with presenters Gus Speth of the Vermont Law School and previously the Yale School of Forestry and Environmental Studies; Tina Clark, a Massachusetts Transition Town trainer; and Chuck Collins of the Institute for Policy Studies.

All of the plenary sessions are open to the public with a suggested donation.

The Slow Living Summit also includes four periods, each with a selection of seven to nine breakout sessions to choose from. These in-depth and highly interactive sessions are being held in the Marlboro Graduate Center, smaller Latchis theaters, and the Brattleboro Food Co-op Community Room. To participate in these sessions requires a full or one-day conference registration.

The breakout sessions include everything from new models of farm cooperatives with Roger Allbee, a past Vermont Secretary of Agriculture, to a session on the “Story of Place” with Kate Stephenson of Yestermorrow, and Bill Reed of the Regenesis Group; an update on nutrient cycling through urine-separation technology, which is being pioneered in Brattleboro (including field trials); and “resilient design” that Bob Stevens and I are presenting that will highlight several local projects.

The Locavore Index

The just-published 2013 Locavore Index. Click to enlarge.
Image Credit: Strolling of the Heifers

With the growing interest in local food and agriculture, including urban farming, the organizers of the Strolling of the Heifers and Slow Living Summit rolled out the Locavore Index in 2012. This metric factors in farmers’ markets, community supported agriculture (CSA) operations, and food hubs, and normalizes an index of those operations by population to rank states according to the availability of local food and agriculture. The metric may not be perfect, but it’s a start at reporting statistics on food production that aren’t often considered.

For the second year in a row, Vermont came out ahead in the 2013 Locavore Index, followed by Maine, New Hampshire, North Dakota, and Iowa (see attached chart). Indeed, some of the results are surprising, while others may not be. Bringing up the bottom of the list are Texas, Florida, Louisiana, Arizona, and Nevada.

A model for other regional events

The Slow Living Summit in the small town of Brattleboro, is a different sort of conference—one that is integrated into the downtown, rather than being housed in a sterile conference center somewhere. Participants will walk through the downtown getting from one venue to another and to the lunch venue.

That some attendees are coming from afar may seem contradictory. The Summit is inherently about localism, but sometimes in achieving locally based solutions we have to look at what’s being done somewhere else. That’s what’s bringing attendees to the Slow Living Summit from distant states and even some foreign countries. And if these attendees take the Slow Living Summit model back home and implement it there, our event will be a success.

With the Slow Living Summit—and the Strolling of the Heifers parade immediately following on Saturday—Brattleboro is at the leading edge of the transition to a more locally based, sustainable, and resilient future. Come and enjoy our town and these wonderful events.


Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-06-04 n/a 17176 Energy Use by Buildings and the Built Environment

If we include building-related portions of industrial and transportation sectors, buildings account for a lot more energy than most people claim

The generally accepted split between different primary energy end-uses. Click to enlarge.
Photo Credit: U.S. Department of Energy, Energy Information Administration

I’ve long appreciated the adage that you can’t manage what you don’t measure, so I’ve spent a good bit of time looking at numbers—especially relating to energy.

One of those numbers that I’ve always been intrigued with is how much of our nation’s total energy consumption relates to buildings. That sounds simple enough.

We are fortunate in the United States that the Department of Energy (DOE) tracks all sorts of energy statistics through the Energy Information Administration (EIA), so a numbers geek can go hog-wild digging as deep as he might want into whatever aspects of energy production and consumption are of interest.

On the energy consumption side, the most common breakdown of end uses is Residential, Commercial, Industrial, and Transportation. The EIA shows the 2011 breakdown of these end-uses as follows: residential 22%; commercial 19%; industrial 31%; and transportation 28%.

In units of energy, total U.S. primary energy consumption in 2011 was 97.3 quads (one quad equals one quadrillion Btus—that’s 1 followed by 15 zeros). Of that, the residential sector totaled 21.6 quads, commercial 18.0 quads, industrial 30.6 quads, and transportation 27.1 quads.

Historical U.S. primary energy consumption by end-use sector.
Photo Credit: U.S. Department of Energy, Energy Information Administration

These fractions and quads are of primary energy use. When we use a kilowatt-hour (kWh) of electricity for lighting in our homes, that’s a kWh at our house (site energy), but to produce that kWh of electricity probably took about three kWh of primary energy. The difference between site energy and primary energy has to due to waste during the production and delivery of energy to our end-uses. With electricity that difference is huge, due to waste heat produced in power generation and losses in transmission. With other energy sources, such as petroleum or natural gas, the difference between primary and site energy is much less.

So, when we look at this end-use split (22%, 19%, 31% and 28%) we’re looking at the primary energy, and 41% of that (22% + 19%), as commonly argued, has to do with buildings. So far, so good.

Having 41% of U.S. energy consumption attributed to buildings is huge. A very similar metric has to do with greenhouse gas emissions. The percentage is slightly different—because some energy sources are more carbon-intensive than others—but the difference is minor. Buildings account for 40% of total greenhouse gas emissions in the U.S. (usually reported as carbon dioxide or carbon equivalents).

These numbers tell us that we need to be paying a lot of attention to buildings if we want to make headway in curbing our contributions to climate change.

If the primary energy used for electricity generation is apportioned to the end-use categories, the totals (in blue) result.
Photo Credit: U.S. Department of Energy, Energy Information Administration

Building-related energy consumption is actually a lot greater

But, I contend that buildings and development patterns actually account for significantly more energy consumption and global warming impact than these numbers suggest.

With the other two segments of energy consumption in the U.S.—industry and transportation—buildings and our development patterns also have a big impact.

Some of the industrial sector energy consumption has to do with heating, cooling, and illuminating factories. Digging deeper into the EIA energy consumption data for 2011, we find that heating, ventilation, and air conditioning (HVAC) accounts for 0.7 quads, and facility lighting 0.2 quads. Those energy uses really fall into the area of building energy consumption (as opposed to the process of making steel or glass, for example).

There is also a portion of industrial energy consumption that has to do with construction materials—the energy it takes to make the stuff we use in buildings houses and commercial buildings. This is often referred to as “embodied energy.” A truly thorough examination of energy use by the building sector would include that portion of industrial energy use for making concrete, window glass, steel I-beams, plywood, and the other building products. I would guess that that is easily a quad or two, though I have not attempted to include that information here.

Transportation energy use related to the built environment

Transportation energy use in the U.S. by mode - 2010. Click to enlarge.
Photo Credit: Transportation Energy Data Book - Edition 31, U.S. Department of Energy

With the transportation sector, the impact of buildings—and where we put them—is a lot more significant. Development patterns have a huge impact on the energy expended for transportation. From the 423-page Transportation Energy Data Book – Edition 31, published by Oak Ridge National Laboratory in July 2012, we find that cars and light trucks accounted for 58.7% of transportation energy consumption in 2010, while medium and heavy-duty trucks accounted for 22.3%, busses 0.7%, air travel 7.8%, ships 5.0%, rail 2.1%, and pipelines 3.4% (Table 2.6).

We further find that for household travel, in 2009, commuting to work accounted for 28.7% of vehicle miles traveled, shopping 15.5%, other family/personal business 15.7%, vacation 2.3%, visiting friends and relatives 9.4%, and other social/recreational 13.5% (Table 8.9).

In Table 8.17 we find that in low-density areas (less than 1,000 residents per square mile) significantly more miles are driven per vehicle per day: 31.6 miles, vs. 18.5 miles when the housing density increases to 10,000 to 25,000 residents per square mile and 14.8 miles with densities above 25,000 per square mile.

Bottom line

What I read into these numbers is that where we build our homes and where companies build their offices and factories has a huge impact on the amount of energy we use in transportation. (I wrote about this in a September 2007 article in Environmental Building News, “Driving to Green Buildings,” suggesting that we consider a new metric of “transportation energy intensity.”)

I would venture to say that a third of all of our transportation energy use relates to building location. We shouldn’t ignore this energy when we’re focusing on the energy use of buildings.

A third of our transportation energy use amounts to 9.0 quads. If we lump that into the expanded column of buildings and the built environment in our initial total of 21.6 quads for residential buildings and 18.0 quads for commercial buildings, and include the 0.9 quads of industrial energy use having to do with heating and illuminating factories, that would mean that buildings and the built environment account for 49.5 quads of primary energy consumption, or 51% or total energy use.

In other words, the direct operation of buildings for heating, cooling, lighting, and appliances, along with a reasonable share of energy use associated with getting to and from those buildings, accounts for over half of our energy use—significantly more than the 41% figure that’s commonly quoted.

This means that those of us involved in influencing how buildings are designed and built and where we build—and that includes building owners—share even more responsibility for the nation’s energy consumption (and greenhouse gas emissions) than is commonly suggested. We have a lot of work to do!

I’d love your thoughts on whether this argument makes sense.

Read more in Environmental Building News:

Getting to Zero: The Frontier of Low-Energy Buildings

Measuring Energy Use in Buildings: Do Our Metrics Really Add Up?

Energy Metrics: Btus, Watts, and Kilowatt-Hours

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-05-29 n/a 17147 America's Greenest Office Building

The Bullitt Center in Seattle is showing that a six-story, 52,000 square-foot building can meet the net-zero-energy, net-zero-water Living Building Challenge

The new Bullitt Center with its cantilevered cap of PV modules. Click to enlarge.
Photo Credit: Alex Wilson

I’m just back from a week in Seattle, where I attended the Living Future Conference, which this year had a theme of resilience and regeneration—a major focus of mine with the Resilient Design Institute. While there I visited what is almost certainly the greenest office building in America if not the world.

The Living Future Conference was created initially to provide a networking and learning venue for designers and builders involved in creating buildings that achieve the Living Building Challenge. Unlike its better known cousin, the LEED Rating System (Leadership in Energy and Environmental Design) of the U.S. Green Building Council, the Living Building Challenge (LBC) is not a points-based system, but rather a collection of very specific, very challenging requirements.

To achieve LBC certification, buildings must:

  • operate on a net-zero-energy basis—using no more energy, on an annual basis, than is collected by the building (LBC certification can not be earned until a full year of data is collected proving that it is actually operating to be zero-net-energy);
  • operate on a net-zero water basis—using no more water on an annual basis than is collected on the site;
  • contain no “red list” chemicals—the LBC maintains a long list of chemicals that cannot be used, including polyvinyl chloride (PVC), brominated flame retardants, and heavy metals like the mercury found in fluorescent lights; and
  • address various other requirements related to the building site, health, equity, and beauty (yes, beauty). Each of these categories (energy, water, materials, site, health, equity, and beauty) are referred to as petals in the program.
Denis Hayes, president of the Bullitt Foundation, explaining features of the building.
Photo Credit: Alex Wilson

Needless to say, achieving LBC certification is very hard. Since the launch of the program seven years ago only a handful of buildings have achieved full certification (4 and counting), and another half-dozen have been recognized for achieving LBC requirements in individual petals. When it comes to larger, multi-story office buildings, the requirements for LBC have seemed almost out of the realm of possibility—at least until now.

The Bullitt Center

The Bullitt Center is a remarkable building that is well on its way to becoming the first sizable commercial office building to achieve LBC certification. The six-story, 52,000 square-foot commercial building, which is owned by (and houses) the Bullitt Foundation, had its grand opening on Earth Day this year (particularly appropriate, since the long-time president of the Bullitt Foundation, Denis Hayes, was the director of the first Earth Day in 1970).

The building was designed by the Miller Hull Partnership in Seattle, with other members of the integrated design team including Point32PAE Consulting Engineers, FousheeLuma Lighting Design, 2020 Engineering and Berger Partnership.

Among the building’s features:

  • Highly energy-efficient building envelope. The mostly glass building has a modeled energy-use intensity (EUI) of 16 kBtu per square foot per year. This makes it 83% more efficient than typical office buildings in Seattle. This is achieved with such features as triple-glazed, low-e, argon-filled windows, automated exterior shades, and high insulating values for non-glazed portions of the building.
  • A triple-glazed, low-e, operable window. The exterior shades can still be deployed with the windows open.
    Photo Credit: Alex Wilson
    Solar-electric system. A rooftop 242-kilowatt (kW) photovoltaic (PV) system is projected to deliver 100% of the building’s electricity needs on an annual basis. Denis Hayes told me, however, that since Seattle isn’t known as one of the sunnier places, this net-zero-energy performance will depend on the weather each year. On a good year, the PV array should have no problem meeting that goal, but some years there is a lot less insolation than average. To get a large enough PV array on the roof to supply electricity for six floors, the PV array cantilevers out over the walls. (Incidentally, Hayes knows what he’s talking about relative to solar, as he served in the late-1970s as director of the Solar Energy Research Institute—now the National Renewable Energy Laboratory—in Golden Colorado.)
  • Ground-source heat pump heating and cooling. Twenty-six, 400-foot-deep wells drilled beneath the building provide a heat source and heat sink for the building. Both heating and cooling are delivered through radiant systems. This all-electric system is projected to use only 5% of the electricity produced by the building’s PV system.
  • Lighting and plug loads. Daylighting will provide the vast majority of lighting in the building. Power consumption for electric lighting and plug loads (computers and other devices that plug into outlets) is kept low in part through a unique, internal “cap-and-trade” system in which tenants have specific energy budgets. If they use less electricity than their budget, they can trade with other tenants in the building who may need more. Tenants sign a thick contract that includes penalties if their energy budgets are exceeded. (The International Living Future Institute, which manages the Living Building Challenge, has just moved into the building so will be able to walk the talk.)
  • Rainwater filtration system.
    Photo Credit: Alex Wilson
    Operable windows. Many of the large triple-glazed windows that comprise much of the wall area of the building are operable. Rather than hinging open, the German Schüco mechanisms keep the windows parallel to the wall as they open, which improves the ventilation. The mechanisms are automated but have manual override. To achieve the LBC requirement for local materials, Schüco partnered with a local glazing fabrication company to produce the units, and that company is now going to be a regional producer of high-performance curtainwall systems.
  • Rainwater harvesting. The building has a 56,000-gallon cistern for storage of rainwater that is harvested on the roof. This water, after filtration and multi-stage treatment and polishing, can supply 100% of the building’s water needs, including drinking water, the three ounces of water used per flush in the foam-flush toilets, showers for bicycle commuters (there are showers on each floor), and landscape irrigation. (Permitting issues are still being worked out to allow the building to use only site-harvested water, but hopefully that will be resolved.) Interestingly, while Seattle is cloudy a lot of the time (225 cloudy days per year) and it rains a lot (150 days per year), Hayes told me that the total rainfall is modest: only 37 inches per year on average, compared with 43 for Boston and 49 for New York City. The exception to the self-contained water system is the building’s sprinkler system, which the city required be on municipal water pressure.
  • Composting toilets. To get the building’s water consumption low enough to satisfy it entirely with site-harvested water required composting toilets. The four foam-flush toilets on each floor (24 total) deliver waste to ten Phoenix composting units located in the basement. As far as I know, this is the only building over four stories to rely exclusively on composting toilets.
  • Phoenix composting toilet vessels in the basement. The first "harvest" should be in about 18 months.
    Photo Credit: Alex Wilson
    Durability. The building’s timber structure is designed for a 250-year life, and the building envelope (or skin) has a projected life of 50 years before it will need replacement—which can happen without affecting the structure.
  • Local materials. Reflecting the Pacific Northwest’s timber resource as well as a desire to minimize embodied energy of materials, all of the structural wood for the building is local Douglas fir from forests that were certified to Forest Stewardship Council (FSC) standards. Glulam beams are produced from two-by dimension lumber. Incidentally, the Bullet Center is the largest heavy-timber building constructed in Seattle since the 1920s.
  • Safe materials. Tremendous effort was expended to avoid the use of several hundred red-list chemicals. Manufacturers whose products were used have to go through the International Living Future Institute’s Declare program or produce a Health Product Declaration to certify that red-list chemicals are not used. This feature of the Living Building Challenge is having a huge influence on product manufacturing today, leading to greener products. A number of manufacturers altered their manufacturing to comply with LBC requirements, so other (non-LBC) projects using those materials will benefit.
  • Occupant comfort and daylighting. All tenants in the building will have access to daylight, either from adjacency to outside walls or through glass interior partition walls. Even the stairwell is fully daylit, a particular requirement of Hayes, who calls it the “irresistible stair” that will encourage occupants to walk rather than taking the elevator. Views of downtown Seattle from the stairwell make the walk worthwhile.
Large banners in the open reception area show off features of the Living Building Challenge, including a list of all banned red-list chemicals.
Photo Credit: Alex Wilson


As might be expected, the Bullitt Center wasn’t an inexpensive building. At $18.5 million dollars, or $355 per square foot, this is about $50/sf above the average for high-quality, Class-A office buildings in the region, according to the Bullitt Foundation. But it is a demonstration of pushing the envelope and proving that the environmental impacts of buildings can indeed be dramatically reduced.

Office space in the building is being leased at $28–30 per square foot per year, slightly higher than average for Seattle, but tenants get free electricity and water at that price—as long as they keep within their allotted limits.

The Bullit Center is indeed a milestone building—I believe one of the most important commercial buildings of the past 50 years.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-05-21 n/a 13956 Mineral Wool Boardstock Insulation Gaining Ground in the Homebuilding World

Roxul ComfortBoard IS has some important environmental and performance advantages over XPS and polyisocyanurate insulation

ComfortBoard IS, Roxul's exterior insulation board, is being distributed nationwide in the U.S. at thickensses up to 3".
Photo Credit: Roxul

Readers of this Energy Solutions blog may be aware that I’ve been critical of some of our foam-plastic insulation materials. I’ve come down hardest on extruded polystyrene (XPS), which is made both with a blowing agent that contributes significantly to global warming and with a brominated flame retardant, HBCD, that’s slated for international phaseout as a persistent organic pollutant.

So I’m always keeping an eye out for alternatives. I’ve written here about two of those alternatives that I’ve used in our own home: a cellular glass material called Foamglas with high compressive strength that works very well below-grade; and Thermacork, an all-natural rigid insulation material made from expanded cork.

I like both of those materials a lot, but they have two big problems: high cost and limited availability. They just won’t be able to enter the mainstream home building industry—not yet, anyway—since they cost more than twice as much as XPS and polyisocyanurate and are hard to get hold of.

Enter ComfortBoard mineral wool boardstock

With this context, I was thrilled to learn recently that Roxul, a Canadian manufacturer of mineral wool (or rock wool) insulation and part of the global, Denmark-based Rockwool International, has been gaining traction with its residential ComfortBoard IS in the U.S. Plus, the company has a new, even higher-density boardstock product coming out this month for commercial applications.

Rigid boardstock mineral wool has been available in the U.S. for decades from at least four manufacturers, and it is widely used in commercial construction. But it’s never been widely available for home building.

That is changing as Roxul ramps up national distribution of ComfortBoard IS, which was first introduced about a year ago. (A few years earlier the company began national distribution of its ComfortBatt product for cavity-fill applications.)

ComfortBoard IS from Roxul’s Milton, Ontario factory is third-party-certified to have a minimum recycled content of 75%, and product can be specified with recycled content up to 93%.

Residential installation of ComfortBoard IS.
Photo Credit: Mark Gorgolewski

ComfortBoard IS, the residential product, has a density of 8 pounds per cubic foot (pcf) and is available in four thicknesses: 1-1/4", 1-1/2", 2", and 3". The company has the capability to produce the product up to 6" thick—which could offer an attractive option for Passive House builders and those interested in deep-energy retrofits—but because thicker panels requires a special production run, those options are only available in truckload quantities.

The insulating value of ComfortBoard IS is a very respectable R-4.0 per inch. That’s lower than XPS (R-5 per inch) and polyiso (about R-6.0/inch), but there will be no “R-value drift” (reduction in R-value over time), which occurs with foam insulation materials that rely on lower-conductivity blowing agents that slowly leak out or allow air to leak in.


A very attractive property of ComfortBoard IS is the high vapor permeability. A two-inch layer of the insulation has is about 30 perms, which means it’s highly "breathable." If the ComfortBoard is installed on the outside of the wall the high permeability will allow excellent drying potential to the exterior. This approach, in which the sheathing layer provides the continuous air barrier, is gaining many fans in the building science community.

ComfortBoard IS has a textured outer surface (see photo), which may even aid moderately in that drying potential (acting like a rainscreen). When asked about this, Paraic Lally, the North American Manager for Specifications at Roxul, told me that the texturing is a function of the manufacturing process and not designed to provide a rainscreen; thus, the orientation of installation is not important..

Another feature of mineral wool that I hadn’t appreciated before is the very low coefficient of thermal expansion with temperature. According to Roxul, the coefficient of thermal expansion of ComfortBoard is just 5.5 (10–6 m/m°C), compared with 80 for XPS and 120 for polyiso. In applications where temperatures fluctuate significantly (like on the outside of a wall in a cold climate) this can be a real problem.

As Martin Holladay has reported on, shrinkage of XPS insulation used as an outer sheathing layer can be significant enough to totally separate the tongue from groove at XPS joints, thus eliminating that thermal break role of the exterior insulation.

Formaldehyde binder

All North American mineral wool today is produced with urea-extended phenol formaldehyde binder. This raises the prospect that the material could release formaldehyde, and it means that the insulation cannot be used in Living Building Challenge projects, because formaldehyde is a "red-list" chemical in that rating system.

From what I understand, however, the high-temperature processing of the mineral wool during manufacture drives off any free formaldehyde, and test data I've reviewed (for the ComfortBatt product, not ComfortBoard) showed formaldehyde levels to be at or below background levels. So, other than the concern that mineral wool can't be used in Living Building Challenge projects, I don't consider the formaldehyde binder a big deal. But I'd love to hear other thoughts about that.

Typically installed over sheathing, if structural bracing is provided, ComfortBoard can be installed without exterior sheathing.
Photo Credit: Roxul

Availability and price

I was pleasantly surprised recently when I asked Leader Home Center in Brattleboro, Vermont to price a number of insulation materials for an update to BuildingGreen's encyclopedic report on insulation. The contractor pricing for ComfortBoard IS came to $0.64 per board-foot, compared to $0.48/bd-ft for standard polyiso, $0.75 for fire-rated polyiso (Thermax), and $1.07 for XPS.

While pricing will doubtless differ in other regions and for different quantities, the fact that ComfortBoard is in the same ballpark as these other materials is great. Even after correcting for the lower insulating value (you need more thickness of ComfortBoard to achieve R-10 than with the foam plastics), Comfortboard IS locally was more affordable than XPS: roughly $1.59 per square foot at R-10 for ComfortBoard vs. $2.14/sf @ R-10 for XPS.

Dimensions and installation

Although Roxul literature shows ComfortBoard IS being available in three sizes—24" x 48", 36" x 48", and 48" x 96"—it is most commonly stocked in the smaller sizes. This may be because the larger panels will be fairly heavy. At 8 pcf, a three-inch-thick, 4' by 8' panel weighs 64 pounds—not an insignificant weight to wrestle into place.

To achieve a reasonably thick, four- to six-inch layer of exterior insulation for a deep-energy retrofit of Passive House wall system will require a double layer (unless you have the ability to order by the truckload). This can be an advantage because is allows overlapping the panel joints (only square-edge product is produced), but it will likely increase labor costs.

Rigid mineral wool may also take some getting used to from an installation standpoint. It can be cut with a hand saw, though I can’t (yet) report on cutting the product from personal experience. Minimum one-inch-diameter washers or nail/screw heads are recommended for attachment, and when strapping is installed on the outside to produce a rainscreen, that strapping has to be screwed into wood studs through the insulation. Because it is mineral-fiber product, a dust mask and gloves should be used when working with it.

Commercial ComfortBoard on the way

Just as exciting as the increased availability of ComfortBoard IS is a commercial version that’s about to be introduced: ComfortBoard CIS. It is similar to the residential product, but produced at a higher density of 11 pcf. Like Comfortboard IS, it can be ordered up to 6" thick, but standard thicknesses will be only up to three inches.

While I am pleased to have used Foamglas and cork insulation on my home, I suspect that Roxul’s ComfortBoard will find its way into my next project.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-05-15 n/a 12735 A Good Time for Energy Audits and Weatherization

Few others are thinking about energy audits and weatherization, but now’s a good time.

Weatherization should target the biggest air leakage sites.
Image Credit: U.S. Department of Energy

Wait a second. Spring has barely sprung, and you’re saying we need to start thinking about energy audits already? What’s up with that?

There are several reasons why now is a good time not only to focus on energy auditing and weatherization—not only for your clients, but also for your own home.

Weatherization professionals have some time

Because spring is a time when few homeowners are thinking about heating bills and how to bring them down, it’s a good time to find energy-performance contractors who can do that weatherization work.

Those energy-performance contractors who do general construction work may be gearing up for the summer building season, but for those limited to energy audits and weatherization, now is a good time.

Still cool enough for thermographic analysis

Part of an energy audit may involve taking images of your house with a special infrared camera to identify areas of excessive heat loss. Infrared or thermographic cameras show temperature differences. Taking such images of your house walls when the house is warm indoors and fairly cold outside will show visually where heat is escaping from the house.

To work well, there has to be a significant temperature difference between the interior of the house and the outdoors. The minimum temperature difference (delta-T) is 20°F, but a higher delta-T is even better.

In more northern climates, such as New England, even though it’s been getting up into the mid-70s during the days this week, it’s been dropping into the low-40s or 30s at night. So a thermographic analysis in the evening or early in the morning can still find plenty of delta-T for the assessment.

Air tightness is key

A huge part of weatherization is tightening up the house. (For why, see Making Air Barriers that Work:
Why and How to Tighten Up Buildings.) To assess airtightness, a blower door is used. As described a few weeks ago, this is a fan that is installed in a door frame and depressurizes the house. A computer controller tells you how tight the house is by calculating how much air has to be forced through the fan to maintain a specific pressure difference—usually 50 pascals.

Andy Shapiro and Terry Brennan setting up a blower door.
Photo Credit: Alex Wilson

Great incentives for energy audits and weatherization work           

I don’t know about other states and utility territories, but in Vermont the statewide organization Efficiency Vermont and the Vermont Clean Energy Network (VECAN) are currently promoting weatherization through the Vermont Home Energy Challenge. Seventy-seven towns in Vermont are participating in this challenge, which will award $10,000 to the town with the highest level of participation.

The goal of the Home Energy Challenge is to encourage homeowners in participating towns to carry out weatherization projects to lower their energy use. The target is getting 3% of homes to complete weatherization projects. In my town of Dummerston, for example, this will mean getting 24 homeowners to carry out weatherization. This is part of a long-term, state-wide goal to weatherize 25% of homes in the state, which will help us with the state energy plan of reducing the consumption of fossil fuels by 90% by the year 2050.

Before and after blower door testing is required as part of the Home Energy Challenge, with a target of at least a 10% improvement in air tightness through the weatherization.

Seventy energy performance contractors statewide are participating in the Home Energy Challenge by discounting their costs of energy audits, and Efficiency Vermont has kicked in $100 per audit to further bring that cost down. Some towns have gone further in discounting the audit cost—in Dummerston, for example, an anonymous donor is kicking in an additional $100 per house (for up to 24 projects), which will bring the cost of an audit down to about $150, from the typical cost of $400 to $500.

Plenty of time to get the work done before winter

Step one should be getting that energy audit to find out what a client’s house—or your own—needs. Find out if there exist incentives for energy audits or weatherization/energy upgrades in your area. (Assuming that such incentives do not exist, consider getting involved to encourage the adoption of such a program.) Even where incentives don’t exist, energy audits and weatherization is usually a good deal financially.

Spending $400 to $500 on an energy audit, and several thousand dollars on follow-up weatherization and energy improvements, will generally be repaid in less than ten years through energy savings. But even if the financial savings (reductions in heating bills) don’t easily justify the investment, the dramatic improvement in comfort realized through such improvements often make such an expenditure worthwhile.

When tightening up homes, it's important not to create other problems at the same time. Tighter, better-insulated homes have reduced heat loss, but also more of a tendency to trap moisture in places it doesn't below. Consider taking, or having your contractor take, our High-Performance Building Assemblies online course for an understanding of how to avoid such problems.

Learning more

For more on energy audits, weatherization, and other energy improvements and to find a specialized contractor doing such work, contact the Building Performance Institute. Another good source of information is is the advocacy organization, Efficiency First. If you’re lucky enough to live or work in Vermont, contact Efficiency Vermont to find out more about the Vermont Home Energy Challenge.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-05-08 n/a 12699 What’s Different About Unity Homes?

Panelized construction, meticulous attention to energy detailing, and a sophisticated computer design system put Unity Homes at the cutting edge of home buiding.

A Unity Homes wall section at the company's Walpole, NH factory. Click to enlarge.
Photo Credit: Alex Wilson

In my blog last week, I provided a little background on Tedd Benson and his evolution that led him to found Unity Homes. This week, I’ll describe some of the features that set Unity Homes apart from both standard home construction and other panelized and manufactured home production.

An emphasis on energy performance

A top priority for Unity Homes is energy performance. The homes have R-35 walls and roofs that vary from R-38 to R-48—depending on the roof spans. (Longer spans require deeper rafters (made from engineered I-joists) with room for more insulation.)

Unity’s R-35 wall does better than some nominally rated R-35 walls, because thermal bridging through the framing is minimized. The wall system uses 9.5-inch-deep I-studs, so there isn’t a lot of higher-conductivity wood.

Unity uses triple-glazed, low-e, argon-filled Loewen windows throughout to control heat loss. With every house, designers consider window orientation and area and usually specify different glazings for different walls—installing windows with a higher solar heat gain coefficient (SHGC) on the south side. I was surprised that the highest SHGC for Loewen triple-glazed, low-e windows is 0.44, while some other manufacturers offer triple-glazed, low-e windows with SHGC ratings up to 0.60. 

Cut-away showing R-35 wall system.
Photo Credit: Alex Wilson

Like me, the folks at Unity Homes (and Bensonwood) are frustrated with what’s available in the way of energy-efficient doors. They have made a lot of headway by pre-building entire entry modules in the factory (with pre-hung doors and all the air sealing needed in the surround), but the doors themselves continue to be a weak point. Tedd let me know that indeed his team has been working on developing a better insulated door, and they expect to have a prototype soon. I’ll keep an eye on that.

The other major energy feature of Unity homes—perhaps the most important—is air tightness. Through a combination of precise cutting of framing members, use of Huber Zip sheathing with taped joints, and advanced European gaskets, Unity Homes achieve the very stringent Passive House standard for air tightness: 0.6 air changes per hour at 50 pascals of pressure difference across the envelope (ACH50). A recently completed Unity Home in Brattleboro (the company’s first) came in at an impressive 0.51 ACH50 in testing by Efficiency Vermont.

A wall-roof panel intersection. Note the dual-bead gasket. Click to enlarge.
Photo Credit: Alex Wilson

Tedd argues—correctly, I believe—that with very tight construction it’s not as important to have a lot more insulation at the roof than in the walls, because there won’t be as much thermal stratification as in conventional houses. In fact, the homes do so well, that single point-source heating systems, such as air-source heat pumps, usually suffice as heating systems—at least for smaller homes.

Scoring energy performance

The HERS Index, for or “Home Energy Rating System," is a standardized metric for reporting the energy efficiency of houses. In the HERS rating system, a score of 100 is a standard new home built to code. A score of zero would be a net-zero-energy home (one that uses no net energy on an annual basis, beyond what is produced by the house). An average existing home being sold today has a HERS rating of 130.

A standard Unity Home should achieve a HERS score of about 40, while the Brattleboro house had a HERS score of 44 (three points were lost because the insulation couldn’t be inspected). Thus, Unity Homes should use only about 40% of the energy of a new home built to code. This energy consumption is low enough that with energy-efficient appliances and lighting and an energy-efficient air-source heat pump, a roof full of solar panels can bring the HERS rating down to zero.

A heat-recovery ventilator mounted in a modular HVAC panel ready for shipping to the site.
Photo Credit: Alex Wilson

It’s not only about energy

Performance is also about durability, and Unity Homes’ meticulous attention to building science and quality control during production should ensure far greater durability than standard homes. In fact, Tedd talks about a 250- to 500-year life for his homes. (With the home my wife and I are building in Dummerston, our goal is a 300-year design life, but such longevity goals are almost unheard of today.)

I’ve visited Tedd’s Walpole, New Hampshire factory twice now, and continue to be impressed with his use of state-of-the art materials and technology from around the world—especially Sweden, Switzerland, Austria, and Germany. I’ve seen materials in standard use by Unity Homes that I’ve never seen before—like dual-bead gasketing that fits into precisely cut eighth-inch spaces between framing members.

Green materials

The life-cycle assessment of materials has also guided decisions with Unity Homes. For example, the company has largely eliminated the use of foam-plastic insulation, due in part of concerns about flame retardants and the high global warming potential of certain products. Instead, cellulose insulation—made from recycled newspaper with borate flame retardants—is used in the walls and roof.

The foam that is used on the foundation walls is extruded polystyrene salvaged from commercial or industrial projects. And timber elements used in the houses—there are a few to serve specific load requirements and add aesthetic appeal—are typically glulam beams, but substitutes are possible, including salvaged timber from old buildings.

Vinyl (PVC) has been largely avoided in Unity Homes, except for wiring and drainage piping. Siding is typically cedar shingles. And zero- or low-VOC materials are used throughout.

Alright, some of those air-sealing materials coming from Europe take a lot of energy to ship here, but Tedd told me that there is interest from the supplier to set up U.S. production here if demand increases sufficiently.

A just-erected Unity Home in Keene, NH. The house went up and was fully closed in in three days.
Photo Credit: Tedd Benson

Speed of construction

Unity Homes go up fast. The onsite assembly of the weathertight shell is usually accomplished in one to three days, depending on complexity and garage options. From there, Unity Homes can be finished quickly because of the open layout and packaging of systems, such as pre-assembled HVAC modules—strategies that had their origin in the Open-Built system described last week. While a standard new homes takes 150 days to build (and some take a lot longer—ask me about that sometime), Unity Homes can get the build cycle down to 35 working days currently, and the ultimate goal is 20 days.

The Homes

When I visited Unity Homes a few weeks ago I was treated to a tour of the company’s OBGrid computer system by Nino Jordan. It’s an impressive system that has evolved over the past 20 years.

Nino Jordan manipulating Unity Home modules on the computer.
Photo Credit: Tedd Benson

Unity Homes offers four different platforms: Värm, Tradd, Xyla, and Züm, ranging from tradition to contemporary. Each of these platforms has 35 to 45 modular elements that can be configured on the OBGrid system, which determines the exact positions and connections as each element, such as a porch or garage, is dragged into place.

The client can see what the house will look like. The next evolution of development is CAD software, called OBCad, will seamlessly compile data about the cost, specifications, production information, and more. The system will even pull in Google Earth and Bing to see how the house will sit on the building site—with actual topography and orientation. Once a final plan is selected after a series of meetings, a detailed materials list is transmitted to the manufacturing side, which includes the company’s German Hundegger CNC machine that cranks out precision-cut framing members.

Bensonwood's German Hundegger CNC machine cutting I-joists.
Photo Credit: Bensonwood

The design software seemed to make the design process so easy—and you can see the cost impacts of that bump-out addition immediately. Honestly, I was blown away. The more houses that are built, the more the system capabilities expand. “Anything we’ve designed and built can be used again, whether it’s a dormer, bathroom, porch, stairway, bathroom, or closet,” Tedd told me.


Driving down cost, as noted last week, is a big priority for Tedd and Unity Homes. The price of new, high-quality, custom homes today is often around $200/square foot, according to the company, while the first Unity Homes are coming in at around $160-$170/sf, including foundation. The company’s long-term goal is to bring that cost down to $130/sf., which would be slightly less than the average cost of a resale home ($140/sf).

Tedd is also a big believer in phased homebuilding and/or DIY participation in the process. In his view, insistence by banks and building officials that homes be absolutely complete before moving in has undermined flexibility and homeowner involvement. He calls this the “tyranny of completion,” noting that “you shouldn’t have to finish what you don’t yet need.” Tedd built his own house, starting 35 years ago, in phases: “We finished it as our family requirements grew and as we could afford it.”

The kitchen in a just-completed Unity Home in Brattleboro, Vermont.
Photo Credit: Unity Homes

Tedd argues that since a long-term mortgage can more than double the original building cost, the best way to save money in homebuilding is to borrow less. For this reason, Unity Homes supports DIY involvement and phased building after the erection of the weathertight shell and completion of critical living areas. The Open-Built system supports this idea by creating accessible cavities for wiring and mechanical systems and using demountable finishes. This allows the incomplete areas to have a loft-like appearance—and not look like a construction zone.

Continuous improvement

Tedd is pretty clear about his aims with Unity Homes. “We think building a house should be fun, and more people should be willing to engage in the building of their own home,” he told me. “Unfortunately, people tend to be deathly afraid of it because it takes so long and is traditionally such a complex and stressful process.” He reminded me of the oft-heard expression, ‘build a house, lose a spouse.’ “What if it only took 30 working days, all costs were known, the build quality was above anything experienced, and it could have a net-zero-energy impact forever?” 

Unity Homes may not quite be there yet, but I believe they are further down that path than anyone else in home building today. (For more on the challenge of building prefab green and affordably, see our EBN feature article on the topic.) The company, along with parent company Bensonwood, employs 80 people in Walpole, New Hampshire.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-05-01 n/a 12664 Unity Homes: Pushing the Boundaries of Home Building

Tedd Benson's latest initiative to reinvent home building—with lower-cost panelized construction

Wall panels being fabricated at Unity Homes' Walpole, New Hampshire factory. Click to enlarge.
Photo Credit: Alex Wilson

A few weeks ago I spent a half day with my good friend Tedd Benson learning about his new company Unity Homes. Yhis Walpole, New Hampshire company is on the cutting edge of home building today, with its focus on energy performance, building science, green building, and (relative) affordability.

This week I’ll describe some of Tedd’s work that led to the creation of Unity Homes, and next week I’ll go into more detail about this new company and the state-of-the-art green homes he and his team are cranking out.

For those not familiar with Tedd, he is responsible—more than anyone—for the emergence of the modern timber framing movement some four decades ago. Initially to save money, Tedd and his brother Steve used timbers salvaged from old barns in 1973 to build a workshop in Alstead, New Hampshire for the fledgling Benson Woodworking Company that they had launched a year earlier. (Steve died tragically in a car accident in 1974, and Tedd and his wife Christine continued the business.)

Tedd Benson and his crew in the mid-70s.
Photo Credit: Bensonwood

Their work with old timber frames—fixing up old ones in the New England homes they renovated and in building their own shop—fueled an interest in this durable and beautiful building system, which was used by our ancestors in Colonial America. Tedd evolved his business to specialize in timber framing, and in 1979 he wrote Building the Timber Frame House: The Revival of a Forgotten Craft, which became the bible of the emerging timber framing movement.

A few years later Tedd and a handful of timber framers in the region launched the Timber Framer’s Guild, providing a forum to share ideas and have fun doing it. (I can attest that the early gatherings of the Timber Framers Guild were indeed incredibly fun, and I look forward to returning to their annual conferences later this year—many years after my last participation in the event.)

An early Benson timber frame raising from the mid-70s--with Tedd's crew and the clients.
Photo Credit: Bensonwood

Tedd’s company, renamed Bensonwood, became a leading builder of beautiful custom timber frames, ultimately producing frames for high-end homes and commercial buildings in 49 states. Here’s our listing of the company from our GreenSpec database. One of the largest frames they ever built is The Vermont Building on Putney Road in our town of Brattleboro, where one can see their handiwork using massive Douglas fir timbers.

A shift to lower-cost homes

But Tedd had growing frustration building houses only for the wealthy. He wanted a building system that would reach more of Middle America. In 1991 the company began the long-term process of standardizing home designs and using computer-assisted design (CAD) software to optimize designs.

Influenced by Steward Brand, Dutch architect John Habraken, and others, in 1994 Tedd developed the Open-Built® platform that allowed easy modification of structures as needs change (a key argument presented in Brand’s book, How Buildings Learn). Design elements of Open-Built included a baseboard raceway that provided access for electrical and data wiring and an accessible ceiling system that could be used for recessed lights, wiring, plumbing, and ducts for heating and ventilation.

A later Bensonwood home.
Photo Credit: Bensonwood

This work led to a longstanding research collaboration with the Massachusetts Institute of Technology (MIT), the Open Prototype Initiative, to develop affordable, flexible, high-performance houses. While Tedd had done some of the earliest work with stress-skin panels for enclosing timber frames (working with Winter Panel Corporation in Brattleboro—now Vantem Panels), he eventually shifted away from foam-plastic insulation with his building system.

In 2010 in this blog I wrote about Bensonwood’s OB Plus wall system, which is a cellulose-insulated panelized wall and roof system. With this system, Bensonwood achieved an extremely tight, R-35 wall system. A frequent traveler to Europe, Tedd adapted leading technologies and materials from Sweden, Switzerland, Austria, Germany, and elsewhere for this building system.

The interior of the above home, with a spectacular frame.
Photo Credit: Bensonwood

One of their European technologies that made possible Bensonwood’s building system has been an automated, precision cutting system made by the German company Hundegger. This is referred to as a CNC (computer numerical controlled) machine. Cut lists produced by Bensonwood’s CAD software are transmitted to the Hundegger, and the pieces are cut at precise angles with dogged consistency and accuracy finer than the increments on standard measuring tapes.

Unity Homes launched

Bensonwood built a number of houses using this approach and has now launched a new company, Unity Homes, to scale up production and drive costs down through manufacturing efficiency, supply chain development, and continued building systems innovation. Tedd thinks they can eventually roll out more than 100 houses per year from their Walpole facility, and if all goes well, production facilities could be built in other parts of the country with the help of investment capital he’s seeking.

“I have long believed that the average American home should have a much higher standard of build quality, durability, and energy performance,” Tedd told me. “In that regard, homebuilding has long been under-performing compared to other industries. In fact, homes have been considered by some to be the most deficient and defect ridden product consumers buy,” he said.

A Unity Home under construction in Keene, New Hampshire.
Photo Credit: Alex Wilson

Tedd believes that we can do better, arguing that homes are important both for the quality of life they deliver and for helping us achieve environmental sustainability. “They should be leading the way in product quality to provide people with uncompromised energy efficiency and long term security,” he says. “It’s our mission to prove that point with Unity Homes.”

Next week, I’ll get into some of the innovative details and features of Unity Homes—including the impressive per-square-foot pricing they’ve been able to achieve.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-04-24 n/a 12639 EcoSeal: A New System for Air Sealing Homes

Knauf Insulation's EcoSeal can provide significant air-sealing prior to installing cavity-fill insulation

Installing Knauf EcoSeal at our farmhouse. Click to enlarge.
Photo Credit: Alex Wilson

Getting back to our Dummerston, Vermont farmhouse this week, I’m reporting on our use of a relatively new product for air-sealing homes: EcoSeal from Knauf Insulation.

First some context: In the building science world, there is growing interest in achieving a robust air barrier at the sheathing layer of a house, with layers inside of that able to dry toward the interior and layers on the outside able to dry to the exterior. To make that work, the sheathing layer has to be tightly air-sealed.

In our house, we used Zip sheathing from Huber Engineered Wood as the sheathing layer with the joints taped. This is an oriented strandboard (OSB) sheathing that has a coating to improve weather resistance and reduce permeability—so it makes a great air barrier. The version of Zip used for wall sheathing is green and the version used for roof sheathing is a reddish color. Huber also makes a high-performance tape that’s used for sealing joints and edges of the Zip sheathing.

In working with an older house, like ours, there are inevitably some irregularities that make air sealing with the sheathing more difficult. With our house (originally built in the early 1800s), for example, there are beams at the top of the eave walls that extend four inches out from the wall plane (oddly), and we had to box those in with the sheathing. There may also be some air leakage at the joints, despite the taping.

EcoSeal comes in a 5-gallon bucket, and the pump unit has a 200-foot hose.
Photo Credit: Alex Wilson

So to achieve an airtight sheathing layer, it helps to add some air sealing from the interior. Some builders use a “flash and batt” system for this: a thin layer of spray polyurethane foam (SPF) is applied against the sheathing from the interior (up to about an inch thick) and the cavity is then insulated with batt or other cavity-fill insulation. The SPF is great at air sealing but pretty expensive as an insulation material, so flash-and-batt is a reasonable solution.

Another solution is to use one of two new products for sealing just the joints and cracks at the sheathing layer. Owens Corning makes the EnergyComplete system, and Knauf makes EcoSeal (warning: this link opens with an installation video that has a somewhat jarring soundtrack).

An acrylic air-sealing system

EcoSeal is an acrylic product that is applied using high-pressure paint-spraying equipment. The installer arrived with two five gallons buckets of the bright-blue acrylic material that was the consistency of very thick paint. The system comes with a long, 200-foot hose, so the pump and bucket can stay in one place in the house while the work proceeds. The pump is very quiet.

The installer started on the first floor and worked methodically around the room sealing all the joints and cracks, them moved upstairs. We had arranged for someone from Efficiency Vermont to come down with a blower door (a device used for testing the air tightness of a house) and run the blower door during the EcoSeal installation.

Jennifer Severidt from Efficiency Vermont adjusting her blower door.
Photo Credit: Alex Wilson

Here’s how a blower door works: a fan in the blower door depressurizes the house enough to maintain a 50 pascal difference is air pressure between the inside and outside—as measured by an integral manometer (air pressure gauge). Instrumentation in the unit calculates the cubic feet per minute (cfm) of air flow going through the fan to maintain the 50 pascal pressure differential.

The blower door, as we used it, did two things: first, it exaggerated the air leakage so the installer could feel cracks that needed sealing; and second, it allowed us to measure the success of the air sealing.

EcoSeal doesn’t expand as it is installed (as do foam sealants), and it takes up to day to fully cure. The cure time depends significantly on the environmental conditions—temperature, humidity, etc. Our house was fairly cool during installation, so the cure time was significant. The material can span up to about a 3/8-inch gap, according to Knauf, and it remains flexible.

Jennifer's blower door showing 651 cfm at 49.3 pascals. The pressure changes with outdoor conditions.
Photo Credit: Alex Wilson

If EcoSeal gets on surfaces where it doesn’t belong (as occurred once during our installation when some got on one of our windows), it easily washes off with water. We were in the house throughout the installation and could barely smell it, so I’m confident that it has low VOC (volatile organic compound) emissions.

Significant measured improvement

When we started EcoSeal installation, the blower door was showing 950 cfm of air leakage at 50 pascals (cfm50). During the course of about four hours of work on the air sealing, that air leakage rate dropped to 640 cfm50. That’s an improvement of a third—not bad.

Given the volume of the house, 640 cfm50 is equivalent to 1.6 air changes per hour at 50 pascals (ACH50), which is very respectable for a new house, let alone a renovation.

Sealing on the second-floor gable wall.
Photo Credit: Alex Wilson

More about EcoSeal

Knauf Insulation introduced EcoSeal in January 2011. It’s still a very new product, with only 100 installers nationwide, according to Brett Welch of the company. He estimates that about 2,500 homes have so far been sealed with the system.

In houses where there hasn’t been as much attention paid to air tightening (no taped sheathing), a more typical tightness achieved is 2.5 – 3.0 ACH50. Welch said EcoSeal has also been used in a few Passive House projects, where air tightness of 0.6 ACH50 must be achieved.

EcoSeal costs $200 - $250 per five-gallon bucket, according to Welch, with 2-3 buckets typically required for a house. He estimates 6-10 hours of labor for an installation, bringing the total installed cost into the $1,000 to $1,500 range. It can be installed at temperatures ranging from 20°F to 115°F, though at the low temperature range, the material in the bucket must be fluid and the cure time is longer. It can be stored at 35°F to 120°F.

A Palo Alto Passive House under construction that used Owens Corning's Energy Complete system.
Photo Credit: Alex Wilson

Similar system from Owens Corning

While Knauf’s EcoSeal is a one-part system, Owens Corning’s EnergyComplete is a two-part system that is foamed in place. It expands slightly as it is installed and sets up very quickly—in less that a half-hour. I don’t have personal experience with EnergyComplete, but visited a Passive House under construction in Palo Alto in late-2010 that had just been sealed with the system, and was impressed with it.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-04-16 n/a 12636 Växjö, Sweden: A Model of Sustainability

Växjö, Sweden embraced the U.N's Agenda 21 and is now a model of sustainability

Växjö Energi AB's wood-chip-fired CHP plant. My host is standing in front of a large steam turbine. Click to enlarge.
Photo Credit: Alex Wilson

My blog last week about Kansas and efforts to outlaw any mention or promotion of sustainability was so depressing (to write as well read) that I needed to find a more uplifting sequel. I needed to remind myself—and readers—that even if some politicians in Kansas don’t want to make the world a better place for their children and grandchildren, that’s not a universal attitude.

There are lots of towns, cities, and countries around the world where planning for the future is a priority and whose sustainability stories are truly inspirational.

I’ll report here on one of those places: Växjö, Sweden (the approximate pronunciation is “VECK’ shuh”), which is often called Europe’s greenest city. Five years ago I had the good fortune to spend a few days in this municipality of 85,000, with an urban core of 60,000.

VEAB's CHP plant provides 29,000 customers with electricity and over 6,500 with heat.
Photo Credit: Alex Wilson

I learned when I visited that Växjö’s interest in sustainability dates back to the 1960s. At that time, the lakes surrounding the city were heavily polluted—its fish inedible and the water unsafe for swimming. The city decided to do something about that and launched a broad effort to clean up the lakes. The success of those efforts started Växjö on a path to sustainability.

A number of city leaders attended and were inspired by the Rio Earth Summit (the United Nations meeting that spawned Agenda 21—which is being vilified by Glenn Beck and places like Kansas and Alabama). Building on Agenda 21, the City Council of Växjö, which at the time was comprised largely of conservative councilors, adopted a resolution with a goal of becoming fossil-fuel-free by 2030.

The city is now 17 years along in that process—half-way. Whether Växjö will meet it’s intermediate 2015 target of a 55% reduction in CO2 emissions remains to be seen; the city has so far reduced emissions per resident by 41% (from a 1993 baseline), and the share of renewable energy use is now 60%.

On a per-capita bases, carbon emissions have dropped from about 4,600 kg (10,100 lbs) per year in 1993 to 3,010 kg/yr (6,600 lbs) in 2009. Roughly 68% of current emissions are for transportation.

The control room of the VEAB plant.
Photo Credit: Alex Wilson

Highlights of Växjö accomplishments: biomass heat and power

A big part of Växjö’s high renewable energy fraction comes from a large wood-chip-fueled combined heat and power (CHP) plant. When I visited in 2007, the Sandvik plant of Växjö Energi AB was serving 29,000 customers with electricity and 6,500 customers with heat, including 5,500 single-family homes. District cooling is also being added to the system.

Sandvik is a “thermal following” plant, meaning that its output is governed by heat demands with electricity output “following” that. Heat from the plant is distributed via a 220-mile (350 km) network of insulated hot water pipes. The main supply and return pipes are 31 inches (80 cm) in diameter, with pipes becoming smaller as they branch off.

There are four boilers in the plant, including smaller back-up boilers that can burn oil, but 95% of the energy output is currently from wood chips that are sourced from a 50-mile (80 km) radius of the plant. The largest boiler can produce 38 MW of electricity and 66 MW of thermal energy. (In Europe both electricity and heat are measured in watts, kilowatts, or megawatts; an output of 66 MW of thermal energy is equivalent to 225 million Btus per hour.)

A biodigester at Växjö's sewage treatment plant.
Photo Credit: Alex Wilson

Solar and wind power

While Sweden is not known for its sunshine, new solar-electric systems are going in along with commercial-scale wind turbines. While I didn’t see any of these in Växjö, I did bike beneath some huge wind turbines near Lund, Sweden and was struck by how quiet they were—just a gentle whoosh, whoosh, whoosh of the slowly rotating blades.

Sewage treatment plant producing biogas

The sewage treatment plant in Växjö that I visited was unlike any other I have seen. A big part of the plant was the large biogas digesters. Organic waste is collected from throughout the municipality and anaerobically decomposed in large reactor vessels to produce a methane-rich biogas. This biogas is used to fuel city buses and other municipal vehicles, including the Volvo my host used to drive me around.

With expansions of the biogas facility expected to be completed this year, Växjö should be able to power the city buses plus 500-1,000 cars with biogas. Like the CHP plants I visited in Sweden, Växjö’s sewage treatment plant was immaculate. One could have eaten off the floor.

Energy-efficient buildings

I visited a number of building projects in Sweden, including a single-family detached home and a multi-family apartment complexes being built to Passive House standards—a German rating system with extremely stringent energy conservation requirements.

Biogas fueling station at the Växjö sewage treatment plant.
Photo Credit: Alex Wilson

A large, eight-story, multifamily building that I toured in Växjö was being built almost entirely of wood. Sweden, like the U.S., is rich in forest resources, and Linnaeus University has a research program focusing on timber construction practices. This focus is motivated in part by the goal of reducing the embodied energy of building materials—part of the goal of becoming fossil-fuel-free.

The transportation challenge

As Växjö works toward its goal of becoming fossil-fuel-free by 2030, the challenge of transportation is becoming more and more significant. The city has done a good job at promoting public transit and bicycle paths, but recognizes that transportation will be the biggest hurdle in meeting it’s 2030 goal.

Ethanol-powered vehicles and a growing focus on electric vehicles will help in achieving those goals.

Local food

Växjö has a goal of increasing local food production from 13% in 2009 to 20% in 2015, with ecological (organic) agriculture growing from 13% to 30% during that same time period.

My host's biogas-fueled Volvo at the Växjö sewage treatment plant.
Photo Credit: Alex Wilson

As we read about places like Kansas and Alabama where sustainability planning is seen as some sort of foreign attack on U.S. sovereignty, it is great to follow the progress in places like Växjö, where sustainability has been taken to heart and is being acted on.

It’s worth noting that the emphasis on energy reductions and sustainability doesn’t seem to be hurting Sweden’s standard of living. By most metrics (life expectancy, infant mortality, physical fitness, leisure time, education, ownership of second homes), Sweden is well ahead of the U.S.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-04-10 n/a 12608 No April Fool’s Joke: Kansas Threatens to Outlaw Sustainability

Fear of Agenda 21 fuels a bill to ban sustainability planning in the state of Kansas

The Konza Prairie in northeastern Kansas.
Photo Credit: Bill Johnson

I love many things about Kansas—from the tall-grass prairies in the Flint Hills where I’ve hiked through rolling hills overlooking grazing bison to the dramatic waterfowl migrations in the Cheyenne Bottoms region in the western part of the state. But a bill currently in committee in the Kansas Legislature makes me wonder whether these natural treasures will be around for future generations to enjoy. Reading about this legislation simply left my jaw agape. At issue is whether the Kansas legislature should outlaw anything that even remotely encourages sustainability planning.

Kansas House Bill Number 2366, “An Act concerning the use of funds to promote or implement sustainable development,” begins as follows:

“Be it enacted by the Legislature of the State of Kansas:

Section 1. (a) No public funds may be used, either directly or indirectly, to promote, support, mandate, require, order, incentivize, advocate, plan for, participate in or implement sustainable development. This prohibition on the use of public funds shall apply to:

(1) Any activity by any state governmental entity or municipality;

(2) the payment of membership dues to any association;

(3) employing or contracting for the service of any person or entity;

(4) the preparation, distribution or use of any kit, pamphlet, booklet, publication, electronic communication, radio, television or video presentation;

(5) any materials prepared or presented as part of a class, course, curriculum or instructional material;

(6) any current, proposed or pending law, rule, regulation, code, administrative action or order issued by any federal or international agency; and

(7) any federal or private grant, program or initiative…”

You can’t make this stuff up!

Defining sustainable development

The sponsors of this legislation aren’t beating around the bush; they are explicit about what they oppose. The bill defines sustainable development as “a mode of human development in which resource use aims to meet human needs while preserving the environment so that these needs can be met not only in the present, but also for generations to come…”

That sounds pretty good to me. I can’t understand what one would find to oppose in that definition of sustainability. That sustainable development can be seen as so evil that it needs legislating against simply boggles my mind. What’s wrong with providing for the needs of future generations?

Agenda 21

The radical right in this country has been gaining tremendous traction in vilifying Agenda 21, a nonbinding plan adopted at the United Nations Conference on Environment and Development, better known as the Earth Summit, held in Rio de Janeiro, Brazil in June, 1992.

Glenn Beck and various Tea Party commentators (wrongly labeled as “conservatives”) have fanned the flames of opposition to Agenda 21, painting it as an evil international conspiracy to deny Americans their property rights. The message seems to be taking hold. In 2012, for example, the Republican Party Platform included the statement, “We strongly reject the U.N. Agenda 21 as erosive of American sovereignty.”

Kansas isn’t alone among states in seeking legislation opposing this supposed threat to our sovereignty. In June 2012, Alabama became the first state to pass legislation related to Agenda 21 when both chambers of the state legislature unanimously passed Senate Bill 477, referred to as the “Due Process for Property Rights” act.

Signed by Governor Robert Bentley, the law “specifically prevents all state agencies and local governments in Alabama from participating in the global scheme in any way,” according to, a website owned by the John Birch Society.

A similar measure sailed through the Arizona Senate, but died in the Arizona House after that body failed to take final action on it before adjourning last year.

Is it evil to plan ahead?

To me, the irony of the Glenn Beck/Tea Party opposition to planning for the future is that such planning should be at the heart of a truly conservative agenda. Conservative Americans should want to conserve resources so that their children and grandchildren will be able to benefit from those resources and enjoy the same comforts and wellbeing that they enjoy today.

Agenda 21 is a voluntary, non-binding action plan for addressing sustainable development. ICLEI – Local Governments for Sustainability, an organization that’s being vilified almost as much as Agenda 21 by Beck and the Tea Party, provides invaluable resources to cities and towns that are seeking to become more sustainable. What could be wrong with that?

The fate of that Kansas legislation

I don’t expect that House Bill 2366 in Kansas will make it into law. The bill was dealt somewhat of a setback when it came out in the national media that the chairman of the committee that drafted the bill, Dennis Hedke, is a consultant to the oil and gas industry. But even if this bill fails, the strong backlash against sustainability is clearly a cause for concern.

If such an extreme act is passed and signed into law, Kansas risks not only estranging itself from what should be the strongly conservative principle of sustainability, but it risks becoming a laughing stock of the nation. 

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-04-01 n/a 12572 Installing Cork Insulation

Climbing the learning curve in working with a new insulation material

Sliding a slab of precisely cut cork insulation against a door jamb. Click to enlarge.
Photo Credit: Alex Wilson

What do you do if you’re a builder and your client (that would be me) hands you a material that no one’s ever heard of, let alone installed in this country, and asks you to insulate his house with it? A lot of smart builders would run the other way. Eli Gould, our partner in the Dummeston, Vermont farmhouse we’re renovating (really re-building), took it on as a challenge.

Last week I wrote about the cork insulation that we’ve installed—the last of it went up at the end of last week. Here I’ll review some of the installation details that Eli and his crew figured out—including such seemingly minor issues as how to cut the stuff.

Planning for the cork months ago

When we first started talking about expanded-cork insulation last summer, we requested some samples to work with. Along with being a designer-builder, Eli has an R&D company, PreCraft, Inc., through which he works on figuring out better building systems and how advanced building components can work together. This involves a lot of prototyping, and Eli jumped at the opportunity to get his hands on some cork.

Eli's crew used various saws to cut the cork, including this specialized tool for timber framing.
Photo Credit: Alex Wilson

Amorim Isolamentos, which manufacturers the cork insulation in Portugal, sent over several bundles of the boardstock insulation so that we—mostly Eli—could figure out how we would use it and exactly what we wanted to order. The material is available in thicknesses from a half-inch to about 12 inches and with square or shiplap edges. The exposed face of the cork we used is about 18" x 36".

From an energy performance standpoint we wanted to achieve at least R-40 in the house walls and achieve that with a combination of cavity-fill insulation in the walls and rigid insulation on the exterior. We planned to use Zip sheathing from Huber Engineered Woods as the air barrier (with all edges and joints taped), allowing the interior insulation system to dry to the interior and a moderately permeable exterior insulation to dry to the exterior.

Had this been new construction, we would probably have picked a very different insulation system that relied just on (less expensive) cavity-fill insulation, but we were dealing with an existing 200-year-old frame as out starting point, so we decided early on that exterior rigid insulation would be part of the system, and to meet our R-value goals we opted for six inches of cork.

Because we had installed six inches of another innovative insulation material (Foamglas) on the outside of the new foundation walls, continuing the six-inch, non-structural layer upward on the wall made a lot of sense. The six inches of cork would add about R-21 to the wall system.

An old two-person cross-cut saw removed a much smaller kerf and the large teeth did a good job at removing sawdust.
Photo Credit: Alex Wilson

Shiplap edges

In experimenting with the cork samples we recognized that tight joints—as you can achieve with rigid foam insulation—would be hard to achieve with the product, so we wanted to avoid joints extending through the material. Installing two layers of 3" cork was an option, overlapping the joints, but we opted to order 6" material with shiplap on all edges so that through-gaps would be avoided.

Working up from the foundation, the bottom edge of the first course of cork was beveled to match the drainage bevel that we created with the Foamglas foundation insulation. That first course was installed on top of a metal termite-flashing layer that our roofer, Travis Slade, made up.

The shiplap was configured so that any moisture running down the outside of the cork would remain on the outside and not extend through it. At the corners of the building, the overlaps were tricky—but needed to ensure that no gaps extended through. Frankly, I’m not sure how Eli’s crew figured that out—but they did a great job.

The sloped sills in the window surrounds made for some tricky cuts.
Photo Credit: Alex Wilson

Cutting cork insulation

Just about every conceivable option was tried for cutting the cork: from tools our great-grandfathers would have used to high-tech timber-frame tools. The large teeth on a two-person crosscut saw proved very effective at minimizing the kerf thickness and keeping the kerf cleaned out as they cut, but a chainsaw-like timber-framing saw proved best for bevel cuts, though it created at fairly thick kerf.

One of the nice things about working with cork is that all the sawdust on the ground from the cutting is fully biodegradable. In fact, it may make a nice mulch!

Complicated angle cuts

There was really tricky detailing at the window surrounds. The bottom and top edges of the surrounds (see my earlier blog on window surrounds) are pitched, so the cork insulation had to be cut with a matching bevel and slid in. We wanted a fairly tight fit for energy-performance reasons, but they had to be able to slide the cork in. And in doing so, they had to make sure that the pre-applied Pro Clima Solitex weather resistive barrier (housewrap) on the window surrounds would remain exposed so that it could be properly overlapped and taped to the housewrap being installed on the whole house. Tricky detailing indeed.

Similarly challenging details had to be dealt with at the roof edge—both at the eaves and gable end, but the completed job looked great! Sadly, the cork is now hidden by the housewrap, but I loved admiring it before it was covered.

To hold the cork in place we used angled screws through the thinner top of the panel. Strapping will be screwed into the framing to hold the cork tightly.
Photo Credit: Alex Wilson

Securing the cork

As the sheets of cork were attached to the wall, the upper shiplap edge was screwed into the framing with angled screws. Once the housewrap layer is entirely installed, full-dimension, 1" x 3" strapping will be installed vertically and screwed into the framing with 8” Simpson Strong Tie screws. The screws will be countersunk into the strapping, providing a little over an inch of purchase into the Zip sheathing and framing. Horizontal clapboard siding will then be nailed onto the strapping.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-03-27 n/a 12564 Cork Insulation on Our Farmhouse

Why we chose cork exterior insulation for our net-zero-energy house

Installing cork insulation on our farmhouse. Click to enlarge.
Photo Credit: Alex Wilson

Among the innovative—some might say weird—products we’re trying out at our Dummerston, Vermont farmhouse, none is more unusual than the expanded cork insulation we’re currently installing as a layer of exterior rigid insulation. As I mentioned in a blog last summer, cork insulation has a great story behind it.

Cork? You’ve got to be kidding!

I first learned about expanded cork insulation years ago when exploring the attic of a 1920s-era home in Brattleboro. I found a rigid boardstock insulation comprised of cork with plaster on one side. It was made by Armstrong, which was then a company making cork products but is today one of the world’s leading manufacturers of flooring and ceiling products.

It turns out that the product was invented by accident in 1893 in New York City by a boat builder, John T. Smith. The cork granules he used to fill life preservers became clogged in a large tin funnel, and that slipped into the coals of a fire used to steam oak staves. When the owner of the shop discovered the tin funnel the next morning he expected the cork to be burned up, but instead it had expanded to fill the form and solidified into a solid block.

Smith experimented with the process and patented it as Smith’s Consolidated Cork, which he licensed to Armstrong. It was used for several decades for insulating buildings—especially cold-storage buildings. The apple storage building at historic Scott Farm in Dummerston, built in the 1920s or ’30s, is insulated with this product.

Detail of the cork insulation. Click to enlarge.
Photo Credit: Alex Wilson

Why I like cork

Cork is a remarkable material. It is the outer bark of a species of oak tree (Quercus suber) native to the Western Mediterranean region. This thick, spongy bark protects the trees from fire. It can be peeled off every nine or ten years, and grows back. The bark is still harvested in Portugal, Spain, Algeria, Morocco, Tunisia, France, Italy, and a few other countries much as it was 2,000 years ago.

The primary use for cork is for wine bottles. The “corks” we all know are punched out of the bark in a really simple process. The residual cork (about 65-70% of the material) is processed into granules that are processed into a wide variety of uses.

To make cork flooring, floor underlayment, and gaskets, the granules are glued together and sliced into thin layers. Cork makes a great flooring material, because it is soft underfoot (resilient) and it absorbs sound. You will often find it in libraries, for example, due to those acoustic properties. My aunt and uncle installed cork floors in their Connecticut house in 1951, and that flooring is holding up very well more than 60 years later.

Cork is produced from ecologically rich forests that support significant biodiversity, including the endangered European lynx.

The cork arrived three-to-a-pack, and we've been storing it in our barn all winter. Click to enlarge.
Photo Credit: Alex Wilson

Avoiding foam insulation

The primary reason I’m excited about using cork insulation on our house is that I don’t like some of the chemicals used in conventional foam insulation. Extruded polystyrene is made with a blowing agent, HFC-134a, which is a very potent greenhouse gas that is contributing to climate change, and nearly all foam insulation materials contain hazardous brominated or chlorinated flame retardants. I’ve most recently written about these concerns here.

Cork, by contrast, contains nothing but cork—nothing! As it is produced today by Amorim Isolamentos, S.A., the granules are poured into large vats and heated with steam in an autoclave at about 650°F for 20 minutes. The heat expands the granules by about 30% and releases a natural binder, suberin, that exists in the cork. There are no added ingredients.

Isn’t cork a limited resource, or isn’t there a cork blight?

I get these questions whenever I mention cork. As far as I can tell, these were rumors that were started by companies making synthetic bottle stoppers for the wine industry that were trying to take away market share from natural cork. No, to the best of my knowledge there isn’t a blight.

Bundles of cork awaiting installation.Click to enlarge.
Photo Credit: Alex Wilson

Cork is a somewhat limited resource, so cork insulation will never come to dominate the rigid insulation market. But the resource is not disappearing and clearly it is a renewable resource.

The sad part of the story is that as synthetic corks and screw-lid wine bottles have replaced traditional natural-cork bottle-stoppers, the demand for cork has dropped. I’m told that in some parts of the western Mediterranean region, cork oak forests are being cut down and the land converted to other uses.

Shipping cork to Vermont from Portugal

I’ll admit that shipping cork across the ocean is a significant downside. While ocean shipping is very energy-efficient (far more efficient than shipping over land), the fuel used—a low grade of diesel—is very dirty. I struggled with that as I thought about the use of this material for our house. I’ve reviewed an analysis Amorim Isolamentos has done on the carbon footprint of their material, and it’s not too bad.

Detail of the cork.Click to enlarge.
Photo Credit: Alex Wilson

Ultimately, I decided that by publicizing our use of this material I would help generate demand that might help preserve the cork forests. I don’t expect that the U.S. will ever become a huge market, but for people wanting natural and rapidly renewable building materials or who have chemical sensitivities, cork is an option that can be considered. (Relative to chemical sensitivities, care should be taken to make sure that there isn’t sensitivity to the odor of expanded cork, which has a somewhat smoky smell—no doubt due to the heating.)

Our use of cork insulation

We are installing cork as a layer exterior insulation on our farmhouse. The air barrier for the significantly rebuilt early-1800s house is a fully taped and airtight Zip sheathing layer. On the interior of that will be 7-1/2” of cavity-fill insulation. On the outside of the sheathing is the 6” layer of cork.

The building enclosure is designed so that the cavity-fill insulation layer can dry to the interior (if it ever gets wet), while the cork can dry to the exterior. On the outside of the cork will be a layer of housewrap (a high-performance German product, Pro Clima Solitex, distributed by 475 High Performance Building Supply), vertical strapping to create a rainscreen, and wood clapboard siding.

Installation proceeding. Click to enlarge.
Photo Credit: Alex Wilson

We ordered the cork with shiplap edges so that joints would not extend all the way through the material. We had debated ordering 3" thick cork and overlapping the joints—and that strategy would have worked fine—but we decided that we could save on labor with the thicker panels.

Next week I’ll provide some specifics on how the cork insulation is being installed. Eli Gould and his crew have done a wonderful job at figuring out how to work with the stuff—some of the details are quite tricky.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-03-19 n/a 12551 Windows 2.0 – Report from Leonard Farm

Building complex window surrounds for a deep-energy retrofit

Insulated, splayed window surrounds that will frame the exterior wall insulation. The Pro Clima housewrap on the window surrounds will be taped to the wall housewrap after insulating. Click to enlarge.
Photo Credit: Alex Wilson

A few weeks ago I reported on the amazing, high-tech Alpen, R-12 (center-of-glass) windows that we installed on the north and west facades of our farmhouse in Dummerston, Vermont. At that time I promised to report on the other windows we were installing on the south and east facades (windows 2.0 if you will).

First some context:

With our new home, we are creating a demonstration with dozens of cutting-edge energy-saving and green building features and products that one can include in a new or existing home. As someone who has written about such products for several decades now, this is a lot of fun—though the decision-making often remains a challenge, since there are so many great products and materials to select from.

With our house—the rebuild of a 200-year-old Vermont Cape—we wanted to demonstrate what one might do to dramatically improve the energy performance of existing windows if those windows are in good enough shape that one can’t justify replacement. So that’s what we set out to do on the south and east facades—only we installed new windows, because what had been there (installed in the 1970s I suspect) were small and didn’t serve our needs.

In our product research, we were looking for was a solidly built wood window that would look great in an historic home, not cost too much, and offer reasonable performance.

Two members of Eli's crew pre-fabricating a window surround. Click to enlarge.
Photo Credit: Alex Wilson

Good quality, honest wood windows

The new windows we installed on the south and east walls are wood, double-hung Norwood windows with a high-solar-gain low-e coating. They are made in New Brunswick, Canada, reasonably affordable, and—by most standards—energy efficient. But the center-of-glass R-value is only about a third of what we achieved with our high-tech, quad-glazed, triple-low-e coated, Alpen windows.

We decided to install these windows in the plane with the wall sheathing (Zip sheathing from Huber Engineered Woods serves as the wall system’s air barrier) and then build window surrounds to frame the six inches of exterior insulation to be installed on the walls. This will be a fairly common need with existing houses if we are to carry out “deep-energy retrofits” that rely on exterior insulation.

Roofer Travis Slade and some of his handiwork. Click to enlarge.
Photo Credit: Alex Wilson

Our Norwood windows use a specialized low-e coating from Guardian Glass Industries. It is a sputtered coating (like most low-e coatings being used today), but it has very high transmissivity. In other words, it is highly transparent, both to visible light and solar heat gain.

Both of those glazing properties were important to us: the visible light because we want our house to have as much daylighting as possible with unimpeded views of the gorgeous surroundings; and the high solar heat gain because, on the south, we want to benefit from passive solar heating.

The windows use Guardian’s ClimaGuard 75/68 glass (PDF file), and in our double-glazed configuration with a half-inch gap filled with argon, the windows provide 75% visible light transmittance, a solar heat gain coefficient (SHGC) of 0.684, and a U-factor of 0.275 (R-3.64).

Ready for storm windows

We were willing to accept the relatively low R-value (3.6 is a far cry from 12.2 that we achieve with the Alpen Windows), because we’re planning to add high-performance storm windows toward the outside of the window surrounds. We haven’t figure out exactly what type of storm window we will add, but our designer-builder, Eli Gould, designed the window system with an added storm in mind.

Eli refers to our window surround system, which can accept storm windows, as the WindowPLUS™ system. Functions include extending the wall out to the plane of the exterior insulation, providing a framework for the sophisticated system of air-sealing and weather-protection components, providing a thermal break at the window edge, housing the high-performance storm windows, and potentially providing a space to house a hidden, roll-down screens or shades.

Specialized peel-and-stick tapes from 475 are being used to produce weather-protected and airtight window installations.
Photo Credit: Alex Wilson

Our hope with the storm window is to work with some leading manufacturers to envision and build the ideal storm window for deep-energy retrofits. It will be highly durable with a frame made of either aluminum or fiberglass, and it will include low-e glass. We’re trying to figure out whether it will include an integral screen with an operable glass panel, or whether—like old-fashioned storm windows—require seasonal removal. The more durable storm window will also offer protection of the wood-framed prime windows..

With our application we are trying to determine whether having two low-e coatings—one on the prime window and one on the storm—will cause the temperature between the two windows to get too high. This may inform the type of low-e coating we use or other material decisions. With older prime windows that don’t include low-e glass, this wouldn’t be a problem. In fact, we would like to see a storm window developed that could be configured with insulated, low-e glass for an even higher level of performance.

Splayed window openings

Another great feature of Eli’s WindowPLUS system—one that took some real figuring—was to splay the openings so that more light will enter and the view out will be less restricted. Our total wall thickness will be about 15 inches, and without the splayed openings it might seem that one is looking out through tunnels.

Norwood window installed prior to adding the window surround.
Photo Credit: Alex Wilson

Eli developed a system that allowed these splayed window frames to be pre-fabricated and installed with lapped weather barriers (high-tech German products that we got from 475 High Performance Building Products, a specialized product distributor targeting the Passive House movement) and a pre-formed metal sill cladding.

Next-up: the tricky installation our exterior cork insulation.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-03-13 n/a 12547 A Pioneer of Low-Energy Homes Since 1973

Bruce Brownell's impressive track record with foam-insulated low-energy homes

Bruce Brownell has been building low-energy passive solar homes for four decades.
Photo Credit: Adirondack Alternate Energy

Bruce Brownell, of Adirondack Alternate Energy, has been creating low-energy, largely passive-solar-heated, resilient homes in the Northeast for forty years—and he’s still going strong. Since 1973, Bruce has built more than 375 homes in 15 states, a third of them in very cold (over 8,500-degree-day) climates. Most require just a few hundred dollars of heat per year.

Bruce told me that he’s done enough monitoring to know that even in very cold climates his houses will never drop below 47°F if the power and supplemental heat is shut off. The fact that these houses will never freeze makes them popular as vacation homes; they can be left closed up with no heat all winter without worry.

I’m surprised that Bruce isn’t better known. While a few of us hold him up on a pedestal as one of our leading low-energy pioneers, most of today’s low-energy designers and builders have never heard of him. I’ve pondered why that’s the case, and I think it must be that Bruce just rubs some people the wrong way.

Always a renegade

I’ve known Bruce since the early 1980s, having met him at numerous solar conferences. I can remember getting into arguments with him back then about some of his ideas. I recall, for example, him arguing that caulk is a bad idea, and he has always shunned heat-recovery ventilators.

Bruce’s strong opinions turned off a lot of people, I think, including editors of the periodicals we all read. So his houses haven’t received a lot of attention. But he keeps at it, and his track record is certainly impressive.

Bruce is still building much as he was in 1975, though with a few refinements over the years. And his houses seem to keep working—really well. He’s done informal monitoring of hundreds of these homes, and the New York State Energy Research and Development Authority (NYSERDA) has done more in-depth monitoring of a few of them.

Occasionally, weather events have tested his houses. Bruce told me recently that when a 1988 snowstorm knocked out power for three weeks, some of his homes served as refuges, with the owners’ friends or family moving in. The same thing happened with the January 1998 ice storm that knocked out power for up to six weeks in parts of the Adirondacks.

A 1986 home built by Adirondack Alternate Energy in Northville, New York. Click to enlarge.
Photo Credit: Adirondack Alternate Energy

What makes Bruce’s homes perform so well?

His houses are all wrapped with four inches of polyisocyanurate insulation—using two layers with overlapping joints and all seams taped. All six sides (walls, roof, floor) are insulated with this system. Bruce claims this achieves about R-36; I suspect that it’s no more than R-30—and probably less that than. But because it’s a continuous layer of insulation, not thermally broken by wall studs or rafters, and because it’s fairly airtight, the performance seems to be very good.

A big part of the performance comes from passive solar design features (augmented by fans). Adirondack Alternate Energy houses are oriented with a long wall and much of the window area facing south. A small fan pulls air from the peak of the house down through an airshaft and into a network of pipes buried in a bed of 70-100 tons of sand, providing thermal mass.

Heat from this thermal mass radiates upward into the house. Backup heat can be supplied by a wood stove, domestic water heater, boiler, ground-source heat pump, or air-source heat pump.

This house air is filtered using a moderately efficient (MERV-8) filter, which removes most dust and other particulates. Bruce doesn’t believe a heat-recovery ventilator is required, and while I don’t agree, it seems from anecdotal evidence he reports that his approach is keeping occupants healthy. 

Keeping all the wood on the interior of the insulation allows it to dry out, and it sounds like there have been virtually no moisture problems over these four decades. Ice dams never occur, he told me.

What’s ahead?

While most of the rest of us, including the building science community, seem to shift their recommended building practices on a fairly regular basis, Bruce’s Adirondack Alternate Energy keeps at it with a system he’s tested for decades. Bruce is getting older, and I don’t know whether others in his company will carry on his vision of low-energy houses when he retires.

But his completed projects present a larger and larger collection of case studies of a simple system that seems to work well.

While I haven’t always agreed with Bruce, I admire his tenacity. He is indeed a visionary.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-03-08 n/a 12468 Is Natural Gas Going to be Our Savior?

A gradual shift in the supply-and-demand balance for natural gas and increasing shipments of LNG will bring the prices back up, while the risks of fracking continue to be debated

Gas well in the shale country of Pennsylvania. Click to enlarge.
Photo Credit: Philly Workers Voice

In many parts of the country and for many applications, natural gas is considered a panacea to our energy challenges.

Comprised mostly of methane, natural gas is clean-burning, with just a tiny fraction of the particulates, nitrous oxides, and other pollutants that are emitted from burning coal or oil. Because the ratio of hydrogen to carbon is higher with natural gas than with longer-carbon-chain fossil fuels like coal and oil, less carbon dioxide is generated when it is burned. At the point of combustion, natural gas releases about 500 grams of CO2 per kilowatt hour (kWh), compared to about 900 grams for coal. That’s good news in terms of climate change.

And the dramatic upsurge in natural gas production made possible through hydraulic fracturing, or fracking, has cut prices dramatically over the past five years. These low prices have contributed to utility companies replacing some of the nation’s dirtiest coal-fired power plants with advanced, natural gas plants—and this has lead to rather significant reductions in our nation’s carbon dioxide emissions over the past few years.

Natural gas seems like a winner. What’s not to like about it?

The dramatic growth—both today and projected—in shale gas, relative to other natural gas sources. Click to enlarge.
Photo Credit: U.S. Department of Energy

Natural gas supply and demand

A glut of natural gas floods the domestic market currently, and that’s a boon for consumers and many segments of the U.S. economy. It has led to a fairly rapid shift away from oil and coal toward natural gas. Nearly all of the new power plants built in the last few years have been natural-gas-fueled. With transportation, some large fleets, such as UPS and FedEx, are converting from diesel or gasoline to compressed natural gas. So are some urban bus fleets—at great benefit to urban air quality.

But as these conversions continue, the buyer’s market for natural gas will gradually end as demand inevitably catches up with supply. Natural gas prices will rise.

That shift can’t come soon enough for natural gas producers. In a June 2012 presentation to the Council of Foreign Affairs, Exxon Mobil Chairman and CEO Rex Tillerson noted that the wellhead prices being paid for natural gas—then about $2.50 per thousand cubic feet (Mcf)—were far below the cost of production.

“What I can tell you is the cost to supply is not $2.50,” Tillerson told moderator Alan Murray of the Wall Street Journal. “We are all losing our shirts today. You know, we’re making no money. It's all in the red.” (Since then wellhead prices have risen to about $3.30/Mcf in the U.S.—probably high enough for about a third of shale-gas wells to break even.)

The international market will also affect natural gas pricing. In Europe and Asia the wellhead price of natural gas is three to more than five times higher than in the U.S. Natural gas isn’t stored and transported as easily as petroleum, so the pricing tends to be more regional.

As technologies and facilities improve for compressing or liquefying and transporting natural gas, prices internationally are likely to equilibrate to a significant extent—in our increasingly global economy. As many as 15 liquefied natural gas (LNG) terminals are in the works. If approved and built, these could export as much as 21 trillion cubic feet (Tcf) per year—80% of the current U.S. domestic consumption (26 Tcf). 

If just a fraction of these LNG terminals are built—as the conversion from coal to gas continues in the utility sector and from diesel to CNG continues in the transportation sector—natural gas prices can be expected to rise significantly. I will be surprised if we don’t see natural gas above our historical highs (over $10/Mcf in mid-2008) well within ten years.

How fracking works. Click to enlarge.
Photo Credit: Al Granberg, Political Climate

Shale gas and fracking

The surge in natural gas production in the U.S. and the low prices over the past six years have been driven by shale gas extracted through fracking. In mid-2007, shale gas production in the U.S. totaled less than 5 billion cubic feet per day; by the end of 2011 that production had risen to nearly 30 billion cubic feet per day.

With fracking, water, sand, and chemicals are injected under very high pressure into wells up to several miles deep and extending horizontally up to several more miles. Controlled explosions fracture the 350-million-year-old shale, followed by the injection of fluid under high pressure that extends fractures into the rock. Next, sand or a like material (“proppant”) is injected to “prop” open those fissures so that natural gas can flow out into the pipe and be extracted.

Along with the water and proppants, various chemicals are injected that serve as lubricants, viscosity agents, and anti-bacterial agents to aid in the process. Much of this frack fluid is pumped to the surface, along with highly saline water and various toxic elements from the rock (including barium and arsenic) and must be disposed of. That which doesn’t get pumped back out remains underground. There is very little transparency by the industry on exactly what chemicals are being used and what quantities.

Dramatic growth in shale gas from different formations. Click to enlarge.
Photo Credit: U.S. Department of Energy

Along with the considerable environmental concerns about fracking, there is concern among some experts that just as gas extraction rates increase rapidly with fracking, those production rates will also drop off very quickly. A June, 2011 article in the New York Times raised concern that depletion of fracked gas wells occurs more quickly than with conventional gas wells.

According to petroleum geologist Arthur Berman, Associate Editor of the American Association of Petroleum Geologists Bulletin and director of the Association for the Study of Peak Oil, the annual depletion rate in the Eagleford Shale (which he calls “the mother of all shale plays”) is over 42%.

Fugitive methane emissions

Then there’s the issue of fugitive methane emissions from gas drilling—and particularly fracking. Natural gas is a far more potent greenhouse gas than carbon dioxide, and some experts suggest that as a result natural gas’s contributions to climate change are significantly greater than the CO2 releases during combustion would suggest—though the widely publicized claim by a Cornell University scientist that the greenhouse gas impact of natural gas is greater than that of coal has largely been dismissed.

Converting to natural gas

I would like to be 100% behind natural gas as the fuel of the future. Indeed, I am hopeful that the current low price of natural gas will result in the shutdown of more coal-fired power plants.

Drilling in the Marcellus Shale Formation. Click to enlarge.
Photo Credit: Heyl & Patterson

But I can’t help worrying that when we pump undisclosed chemicals into the ground (“trust us, they’re safe”) and break up geologic strata in ways that alter the flow of groundwater and gases, we’re unleashing a Pandora’s box of problems that our children and grandchildren will have to deal with at a cost of hundreds of billions of dollars—for an energy return that proves fleetingly brief.

My hope is that the low-cost natural gas we enjoy today will continue to spur the transition away from coal while buying us enough time for the truly clean, nearly greenhouse-gas-free, renewable energy sources like wind and solar to gain the foothold needed to usher in a lasting green and safe energy future.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-02-27 n/a 12463 FTC Cracking Down on False R-Value Claims

Large fines levied on companies making deceptive claims about R-values

Exaggerated claims, like this one for SUPER THERM, claiming R-19 for a coating of paint, are getting the attention of the Federal Trade Commission. Click to enlarge.
Photo Credit: Superior Products International.

Most of us want to do the right thing in improving the energy performance of our homes. We research energy-saving products like appliances and insulation. We search the internet or clip ads from the paper looking for products that will save us the most energy (and money). We look for the most R-value for the money. Well-meaning homeowners do this all the time.

But it turns out that in a troubling number of situations there’s a significant discrepancy between claimed and actual performance. With insulation materials, for example, exaggerated R-value claims became so rampant in the 1970s—when adding insulation to homes came into vogue following the 1973 oil embargo—that the government stepped in to regulate energy performance claims.

The threat of fines hasn’t been as successful as we might have hoped, as exaggerated claims have long continued. Some long-overdue legal actions against insulation companies in January 2013, however, may finally begin to rein in these scams.

The Federal Trade Commission Finally Doing Its Job

When R-value scams became common in the 1970s, the U.S. Congress passed legislation assigning the Federal Trade Commission (FTC) to the task of policing R-value claims. The so-called “R-Value Rule” was adopted in 1979. That rule helped to some extent, but grossly exaggerated R-value claims have continued.

A $350,000 fine leveled against Edward Sumpolec, doing business as Thermalkool, Thermalcool, and Energy Conservation Specialists, on January 9, 2013 may cause insulation producers and installers to be a little more careful with their claims. These companies were selling both liquid-applied coatings and radiant-foil insulation materials.

According to a January 31, 2013 FTC press release, “Sumpolec’s advertising included false claims such as ‘R-100 paint,’ ‘This . . . reflective coating will reduce wall and roof temperatures by 50-95 degrees . . .’ and ‘Saves 40 to 60% on your energy bills.’” The U.S. Department of Justice, working on behalf of FTC, won the order on the merits of the case, without requiring a trial. This was the largest fine ever levied on an insulation company based on a violation of the FTC R-Value Rule.

Avoiding scams

Inflated R-value claims like Sumpolec’s are so blatantly obvious that most consumers won’t be duped by them. But there are many, many cases where the claims aren’t quite as over-the-top, and it’s very easy for reasonably smart consumers to be duped.

I don’t know how many calls I received over the years from friends and family members who are thinking of contracting to have their attics insulated with radiant-barrier insulation or radiant paint or extraordinarily high-R-value rigid insulation.

If it sounds too good to be true, it probably is.

It’s not just insulation

Exaggerated energy performance claims aren’t limited to insulation. I have often seen ads in our local newspaper’s weekend magazine for seemingly magic electric quartz space heaters, and one can find outrageous savings claims for fairly ordinary windows, exaggerated claims for the benefits of weatherizing services, and highly misleading claims about home-scale wind turbines.

There was even a class-action lawsuit against Honda Motors for unrealistic mileage claims with its Civic Hybrid (we’ve had ours since 2003 and just turned over 170,00 miles).

Share your examples of outrageous claims

Consumers deserve to have access to clear, accurate information on the energy performance of products they buy. And manufacturers who violate that trust deserve to be called out for their deceptive claims. I’d like to compile examples of these outrageous claims and then publicize them—somehow.

(I may have to let my lawyer weigh in on how aggressive I can afford to be in this campaign for truth in advertising.)

Send links to unrealistic energy claims by manufacturers or service providers to me directly, or post comments below.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-02-20 n/a 12426 Commercial-Scale Wind Power

Why larger wind development projects make sense

Two 2.5 MW wind turbines in the Sheffield, Vermont wind project. Click to enlarge.
Photo Credit: Martin Holladay

Last week I wrote about the challenges of small wind turbines and the difficulty of successfully integrating wind power into buildings. This week, I’ll look at larger-scale commercial wind power developments.

Though I have long been willing to point out situations in which wind power is not practical, I am a strong supporter of wind power where it makes economic and environmental sense. It is a critical component of what will have to be a multi-faceted effort to come to grips with our greenhouse gas emissions and climate change. 

A fierce debate is raging about the merits and aesthetics of commercial wind developments in Vermont and elsewhere. Ironically, here in Vermont, a state known for progressive thinking and environmental awareness, our legislature is considering a three-year moratorium on wind power development. How is it that many Vermonters are so willing to fight against a clean, safe technology that offers one of the solutions we so desperately need to solve our climate change conundrum?

Why commercial-scale wind power is the only wind power that makes sense

As I explained last week, there is a tremendous economy-of-scale with wind power. Since the early 1970s, when the modern wind power era emerged following the 1973 oil embargo, wind turbines have gotten larger and larger—from a few kilowatts (peak output) then to a few megawatts today. This is because doubling the output of a wind turbine doesn’t come close to doubling the cost. Larger wind turbines produce far more cost-effective electricity than smaller wind turbines.

By combining multiple wind turbines into larger wind-power developments (wind farms), the necessary maintenance needs can be aggregated. Wind turbines have moving parts and require regular servicing. From a business standpoint, it’s hard to justify sending out a repair technician to service just one machine; servicing a few dozen turbines makes much better business sense.

Large turbines are safer for birds

Large, megawatt-scale wind turbines are also safer when it comes to birds. As a long-time birder, the safety of our avian friends is a high priority of mine. There were horror stories in the 1980s when the thousands of wind turbines in California’s Altamont Pass and Tehachapi Pass caused large numbers of bird fatalities. These 1980s-era wind turbines were very small by today’s standards—most were rated at 25-35 kilowatts—and in a reasonable breeze the blades would spin so fast as to become essentially invisible to birds.

Today’s very large turbines have massive blades that rotate relatively slowly. Birds can see these blades, and fatalities are far lower.

Yes, there still will be some bird fatalities from modern, large wind turbines, just as birds will collide with radio towers on a foggy night. This saddens me, but ultimately the impacts on birds and other species in our ecosystems will be far greater as a result of global warming if we don’t come up with alternatives to fossil fuel combustion—and do so very quickly. (Those with concerns about birds should put their energy into preventing the carnage from house cats.)

Where commercial wind power makes sense

Commercial-scale wind power, in my opinion, makes sense where three conditions apply: where there is lots of wind; where we can use large wind turbines (from several hundred thousand kilowatts to several megawatts in peak output); and where there is enough space to aggregate multiple large wind turbines into wind farms.

Finding windy enough locations in states like Vermont usually means ridgetop locations. In the Upper Midwest it means agricultural land—where it can significantly boost a farmer’s per-acre revenue while having relatively little impact on crops or grazing. In Texas, which now produces more wind power than any other state, it means broad expanses of open grassland.

One of the very best places to put wind developments is offshore, where winds are steady and there are no hills or trees to produce turbulence. I am very excited about offshore wind farms that are proposed for Nantucket Sound, Maine, New Jersey, and Delaware—and frustrated at how long projects have been held up for aesthetic reasons.

One of the Sheffield turbines, which were made in Iowa by Clipper Windpower, a subsidiary of United Technologies Corporaton.
Photo Credit: Martin Holladay

Moving forward with wind power in Vermont

Coming back to Vermont, the bottom line is that if we want a robust renewable energy policy that includes wind power for the state—and I do—we will have to find large tracts of land that include ridgelines. I don’t know the Meadowsend Timberlands site in Windham and Grafton (the potential wind development that is being so heatedly debated today), but the 5,000-acre tract is large enough for there to be an adequate acoustic buffer from adjoining properties, and it must include some ridges where winds are predicted to be suitable for cost-effective wind power generation.

What I think surprises me most about the opposition to wind power around here is the fact that towns where wind farms would be located can realize significant tax benefits. In the little town of Sheffield, Vermont (population 700) between St. Johnsbury and the Canadian border, for example, where a 40-megawatt wind farm went into operation in 2011 after a long battle with opponents, that wind project is projected by the developer, First Wind, to provide $520,000 per year in tax revenue to the town for the next 20 years, plus another $230,000 per year going into the Vermont Education Fund.

Of the $532,000 tax payment received by the town in 2012, according to Sheffield Town Clerk Kathy Newland, 50% was put into a long-term capital reserve fund that will grow dramatically over the years.

With town budgets inexorably going up, I find it remarkable that towns like Windham and Grafton—where Meadowsend Timberlands wants to asses the viability of a commercial wind power facility—aren’t embracing wind power with open arms. Perhaps these towns are a lot wealthier than my own town of Dummerston, but as a taxpayer in Dummerston, I would be jumping up and down if there were a 5,000-acre property owner in town who wanted to develop a wind farm that would lower my property taxes and help our town become carbon-neutral. And I find it ridiculous that many in our legislature want to impose a statewide moratorium on projects like this.

For many, it is an issue of aesthetics. Unlike a lot of people, apparently, I actually find wind turbines attractive. I’d much rather look at the slowly spinning wind turbines on a ridge across the valley than not be able to see that ridge due to smog. Knowing that those turbines are generating power without releasing carbon dioxide into the atmosphere or accumulating nuclear waste makes them all the more beautiful in my eyes.

I suspect that some of the Sheffield residents who had previously opposed the wind farm are coming to think of wind turbines as a little more attractive after seeing the impact on their property taxes and realizing all the benefit that capital reserve fund will bring to their town.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-02-12 n/a 12422 Wind Power: Why it Doesn’t Make Sense Everywhere

I'm a huge fan of wind power, but we should recognize that some applications of wind don't make sense

Aerovironment wind turbines on the Boston Museum of Science. Performance has been poor and Aerovironment has discontinued the product. Click to enlarge. 
Photo Credit: David Rabkin, Boston Museum of Science

At least in our neck of the woods, wind power is very much in the news these days. The Vermont legislature is debating whether to institute a three-year moratorium on what detractors refer to as “industrial wind power,” and debate is raging in the nearby towns of Windham and Grafton, Vermont about a potential wind farm. I figured I should weigh in.

As readers of this blog know, I am a strong proponent of renewable energy, including wind power. But I’m also not shy about pointing out situations in which wind power doesn’t make sense. This week I’m going to focus on those misguided or less attractive wind power applications. Next week I’ll cover where we should be heading with wind power and discuss projects like the one proposed for Windham and Grafton.

Don’t put wind turbines on buildings

Wind turbines almost never make sense on buildings—even tall buildings. When I started researching “building-integrated wind” a few years ago for my newsletter, Environmental Building News (EBN), I thought I was going to write an article that painted a positive picture of putting wind turbines on top of buildings. After all, tall buildings can get the turbines up high where it’s windier, and like rooftop photovoltaic (PV) systems, the power is generated right where it will be used.

But the more I dug into it, the more clear it became to me that building-integrated simply does not make sense.

First, wind turbines installed on buildings have to be small so that they won’t affect the building’s structure, so the power-generation potential is limited.

Second, wind turbines generate significant noise and vibration. That can be okay when the turbines are a quarter-mile away, but on a building it can be a real problem—particularly with a steel-framed commercial building that transmits noise and vibration throughout the structure.

Third, dealing with turbine installations on buildings increases costs significantly. Special attachments are required, and loads may have to be distributed downward through the building.

Fourth, even if the economics work out it’s hard to believe that insurance companies would embrace the installation of wind turbines on buildings. I suspect that insurers would raise insurance rates significantly, due to the increased liability—or perceived liability—of blades flying off wind turbines or rooftop towers collapsing and damaging roofs. Insurance rates wouldn’t have to rise very far for those costs to exceed the value of the generated electricity.

Finally, it turns out that all that wind swirling by tall buildings is highly turbulent. Wind turbines don’t like turbulence; they do much better with like laminar wind flow. Some types of wind turbines apparently do better with turbulence than others, but most don’t perform well in such conditions.

An installation of the Swift Wind Turbine at the Boston Museum of Science. Swift turbines were developed by Renewable Devices in Scotland and are manufactured in Michigan. Click to enlarge. 
Photo Credit: David Rabkin, Boston Museum of Science

The lack of performance data

When I was researching my EBN article, I spent weeks trying to track down performance data on building-integrated wind turbines, but could find almost none. I knew that that data was being collected by manufacturers (up to a dozen manufacturers were producing wind turbines specifically designed for installations on buildings), and the fact that they didn’t want to share it made me suspicious that it was far worse than those manufacturers were claiming.

With a lot of anecdotal evidence of extremely bad performance of building-integrated wind turbines, I got more and more discouraged about the practicality of putting turbines on buildings, and I ended up titling my May, 2009 EBN article “The Folly of Building-Integrated Wind.” Wind turbines don’t belong on buildings.

After my article came out, I finally tracked down some performance data from the Boston Museum of Science, which installed building-integrated wind turbines from five different manufacturers. As I suspected, the performance was terrible—far lower than manufacturer claims. You can learn more about the Museum of Science wind power experiments here.

With ground-mounted wind turbines, smaller is not better

Even when we stick with ground-mounted wind turbines, the performance and economics of small machines (a few tens of kilowatts (kW) of rated output and less) is usually very poor. With wind turbines there is a huge economy of scale. Home-scale wind power rarely makes good economic sense—except in locations where there is strong, steady wind.

I’m disappointed by this. I would really like to think that I could install a cost-effective wind turbine at my home, but I can’t. A good site for wind power—where there a strong 15 mph wind much of the time—wouldn’t be a place you’d want to live. And with small wind turbines you can’t put them too far from the place where the power will be used or fed into the utility grid. So even if your property rises up to a ridge, putting a small wind turbine there may not be feasible in terms of getting the power down to your house or feeding it into the power grid.

Studies I’ve examined where actual performance of small, ground-mounted wind turbines has been collected, the measured output has been significantly below the predicted output. Plus, the maintenance requirements are significant. Compared with the alternative—arrays of PV modules that just sit there with no moving parts—it’s just a whole lot more difficult to justify small wind. The economics usually don’t work.

Next week, we’ll look at where wind power can make sense: much larger wind turbines that can be aggregated into wind farms.

BTW, I’ll be presenting an all-day, pre-conference workshop, Skills for Building Resilient Communities, with three colleagues, Don Watson, FAIA, Joel Gordes, and Maureen Hart, at the Northeast Sustainable Energy Association’s annual Building Energy Conference on Tuesday, March 5th. Details can be found here.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-02-06 n/a 12399 State-of-the-Art Windows Installed in Our New Home

Top-performing quad-glazed windows from Alpen installed with three low-e coatings and krypton gas fill

R-12 windows from Alpen with three low-e coatings and krypton gas-fill. Click to enlarge.
Photo Credit: Alex Wilson

Having written about windows and emerging window technologies for longer than I care to admit (since before low-e coatings even existed), I must say that it’s incredibly fun to be building a house and having an opportunity to try out some of the leading-edge stuff I’ve been writing about.

In my effort to create a “demonstration home,” we are actually installing two very different types of windows in the 1812 farmhouse rebuild that’s underway. On the north and west facades we’re installing state-of-the-art, fiberglass-framed casement and awning windows from Alpen High Performance Products. These windows, which we ordered from Pinnacle Window Solutions in Maine, are the subject of this blog.

On the south and east facades (which you see from the road) we’re doing something very different that I’ll describe in a future blog.

Fiberglass frames

Traditionally, residential windows have been wood-framed. I love the look of wood, and if properly maintained, wood windows can last a long time: the twelve-over-twelve windows in the late-1700s house we currently live in are still hanging on after more than 200 years. But there are drawbacks to wood, including decay and the need for regular maintenance.

Besides wood, the primary materials used for window frames today are vinyl (a misleading abbreviation for polyvinyl chloride or PVC), aluminum, steel, and fiberglass. Due to the very high conductivity, aluminum and steel are less common today in residential windows. Due to its low cost, vinyl has increased dramatically in popularity, finally surpassing wood as the leading window frame material a few years ago.

This quad-pane awning window has two suspended Heat Mirror films. Click to enlarge.
Photo Credit: Alex Wilson

A lot of wood windows try to achieve the best of both worlds with vinyl or aluminum cladding on the exterior (for durability) and exposed wood on the interior. I think this is a nice compromise between appearance and durability and I recommend cladding for most wood windows.

The Alpen windows we installed are fiberglass-framed. Fiberglass is much stronger than vinyl, it has a much lower coefficient of thermal expansion (i.e., it doesn’t expand and contract as much when warmed by the sun and cooled at night), and it has hollow cavities that can be insulated with polyurethane insulation.

Our window glazings are 1-3/8" thick—much thicker than standard insulated glass (typically 7/8” or 1”). With the polyurethane insulation, these frames provide an insulating value of about R-4.3 (U=0.23), as calculated using industry-standard methods. Being fiberglass, they are highly durable and should not require maintenance—though fiberglass does take a coat of paint much better than vinyl, should we ever choose to paint them.

Outrageously high-performance glazing

While standard windows today are double-glazed (two layers of glass separated by an air space), our Alpen windows are quad-glazed—meaning there are four layers of glazing. The inner and outer glazings are 1/8" glass, while the two inner glazings are suspended polyester films.

On three of these layers of glazing there are low-emissivity (low-e) coatings. The outer pane of glass is made by Cardinal Glass Industries and includes a high-solar LoE-180 coating on the inner surface of that pane (the #2 surface in window-industry parlance). This low-e coating is appropriate in northern climates because it lets a lot of solar gain through and it’s clearer to look through.

The suspended polyester films both have Heat Mirror 88 coatings (on the #4 and #6 surfaces). Heat Mirror, made by Southwall Technologies, was actually the first type of low-e coating to be commercialized back in 1981. Heat Mirror coatings are available in various forms (HM88, HM77, SC75, HM66), with the number indicating the transmittance through the glazing; HM88 allows the most solar gain.

This bladder contains krypton and is connected to the inter-glazing space in the window. It allows for pressure equalization during shipping; the connecting tube will be crimped and cut. Click to enlarge.
Photo Credit: Alex Wilson

Another important strategy for reducing heat loss through windows is to substitute a low-conductivity gas for air in the air space. Argon is commonly used as a gas-fill, and for windows the size of ours replacing air with argon would boost the insulating performance by about 28%. For our windows, though, Alpen used a mix of 90% krypton and 10% air. This results in a 40% improvement over argon and a 79% improvement over air!

Energy performance

So what do all these bells and whistles provide in terms of energy performance? I was astounded when my friend at Alpen, Robert Clarke, sent me the following performance numbers:

  • Performance for the glazing only (calculated using Window 6.0):
  • Center-of-glass R-value: 12.2 (U=0.082)
  • Solar heat gain coefficient: 0.44
  • Visible transmittance, Tvis: 62%
  • Light-to-solar gain ratio (Tvis/SHGC): 1.4
  • Passive performance coefficient (SHGC/U-factor): 5.3
  • Winter interior glass surface temp. (assuming 0°F outdoor, 70°F indoor, 12 mph wind): 65°F
  • Acoustic control (STC): 34
  • UV blockage (380 nm): 100.0%

The National Fenestration Rating Council (NFRC) has developed methodologies for testing and reporting unit or full-frame window performance. Our window configuration has not gone through that NFRC testing, but estimated full-frame values are as follows:

  • R-value: 8.3 (U=0.12)
  • Solar heat gain coefficient: 0.39
  • Visible transmittance: 51%

An R-12 window (R-8 unit value) is hard to believe. This insulates as well as a 2x4 wall insulated with fiberglass, yet also brings in significant solar gain and daylight, while providing clear views to the outdoors. I look forward to reporting on the performance and durability of these windows over time.

Alpen HPP a leader in window technology

We have installed these exceptional windows partly as a research experiment. Since our house will not be up to Passive House standards (a rating system that originated in Germany for super-low-energy homes), I’m not sure we would have been able to justify such high-performance windows if Alpen’s Robert Clarke hadn’t wanted me to have them and provided them at a great price.

I’ve known Robert and his company Alpen, for many years. He and Alpen have been the leaders with high-performance windows in the U.S. since way back in the mid-1970s, consistently way ahead of the curve in introducing new technologies.

Several years ago Clarke sold Alpen Windows to Serious Materials, a venture-capital-funded company that sought to change the world with innovative products and materials. But Serious Materials may have spread itself too thin, and there were some quality-control problems with their windows.

Last year, Robert and a partner were successful in buying back Alpen from Serious Materials. I’m hopeful that the company can regain its stature at the top of the window-performance pack—and give the European Passive House windows a run for their money.

It is thrilling to have installed in our home in Dummerston what may be among the highest-performance windows in the country.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-01-30 n/a 12392 The Challenge of Exterior Doors

My struggle to find reasonably energy-efficient exterior doors for our new house

The wood-like fiberglass door we found for our farmhouse. Click to enlarge.
Photo Credit: Alex Wilson

Despite the chilly (seasonable) weather, work is progressing on the renovation/rebuild of our house in Dummerston. Last week, the three exterior doors were installed. Which brings me to one of my pet peeves: the lack of really good choices for highly energy-efficient exterior doors.

We ended up with a solution that I think will be okay, but there is a huge void in the world of truly high-performance doors. Here, I’ll describe the three doors we put in. I hope you can put up with my whining.

The front door

The purpose of front doors, I’m told, is to look nice. But I also wanted a front entrance door that would remain stable and airtight over many years or service and that would provide reasonable insulating value. Oh, and I didn’t want to spend more than about $2,000 for it. That proved a challenge.

I would have loved to install one of the gorgeous custom entrance doors made by Steve Benson’s company, J.S. Benson Woodworking, in Brattleboro. They are custom-fabricated of durable and highly stable triple-laminated mahogany (sustainably produced wood certified by the Forest Stewardship Council is available), but as solid wood, there is very little insulating value: maybe R-3 for a 2-3/4”-thick door.

For Benson doors with lites, the energy performance gets a little better, because Steve has access to super-high-performance glass from Alpen Windows in Colorado. Those lites can provide an insulating value of R-5 or even more—significantly higher than the solid door.

Steve’s beautiful doors have one other drawback: they cost an arm-and-a-leg, starting at about $5,000. A little rich for our budget.

Remarkably wood-like face of our Jeld-Wen door. Click to enlarge.
Photo Credit: Alex Wilson

A high-end fiberglass entrance door

When I was researching doors for the house at Leader Home Center, I came across a Jeld-Wen door made of fiberglass but with a knotty-alder grain that looks remarkably like real wood—and I say that as someone who pays close attention to wood and can readily distinguish most species based on the grain. One could easily be fooled into thinking this door was real alder!

This door looked good. It was solidly built, yet it had a polyurethane insulation core, significantly boosting its R-value. I had already researched fiberglass vs. steel, and found that most energy experts preferred the former, even though magnetic weatherstripping can be used with steel.

“That’s the one I’d like,” I told Russ Chapman at Leader, referring to the knotty-alder floor sample. (Russ had been incredibly patient with me as I picked his brain for energy-performance information.) He said he’d price it out and get back to me.

Oops. It turned out that Jeld-Wenn had discontinued that model as a stock item; that particular door had been on display for three years. A similar door was still available, but it’s now a fully custom, hand-made option, and instead of costing around $2,000, it was going to cost something like $10,000!

“So what about buying this display model,” I asked Russ? It had a few dings, but would suffice. He figured out a nice price for it (the floor model wasn’t doing them much good, since that door wasn’t really available anymore as a reasonably affordable product).

Because we couldn’t get a matching side-lite in the same knotty-alder wood, we had the door hung with a totally different, painted side panel. The glass for that side panel is reasonably good: double-glazed with at least 5/8” separation between the panes of glass, argon-fill, and a low-e coating. We went with a continuous glass panel to minimize the greater edge losses that occur with true divided lites. I think it will look great when the house is sided.

A much less expensive fiberglass-core back door. Click to enlarge.
Photo Credit: Alex Wilson

Cheaper back and side doors

For the back door into the porch and side door into the garage we wanted less expensive doors that were going to be well-insulated and tight. We opted for fairly run-of-the-mill fiberglass doors with upper glazing panels; these are also made by Jeld-Wen and cost us about $300 apiece.

These aren’t anything like the wood-like fiberglass entrance door in appearance (you could never mistake them for real wood), but like the front door, they have a polyurethane insulation core. Because there’s less structural reinforcing material in these doors, they may actually outperform the front door from an energy standpoint. I’ll be very curious about this and will plan to do some thermographic (infrared) analysis once the house is completed and lived in to study heat the relative loss through the different doors.

We still need better door options

I think the three exterior doors we ended up with provide a reasonably good compromise in appearance and performance. But compared with other energy features of the house (R-40 walls, R-50 roof, mostly triple-glazed windows, etc.), the doors are still a weak link.

I would love to see a high-quality, durable, energy-efficient, and reasonably affordable door introduced. Even at the high end—where customers have unlimited budgets and want to create a dream house that can be heated using solar panels on the roof—well-insulated doors are very hard to find. In Europe there are some good doors used for Passive House projects, but these tend to be very expensive.

Is anybody looking for a product development opportunity?

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-01-23 n/a 12383 Changing Behavior to Save Energy in Getting Around

Ease off on the gas — and other behavioral changes to reduce energy for transportation

A no-idling sign in my home town to remind residents not to idle their cars.
Photo Credit: Stan Howe

Before the holidays I wrote a blog on how to save energy in the home by changing our behavior. This week we’ll take a look at some of the ways that we can save energy by changing our driving behavior. Below are some simple measures—most cost nothing and some even save money—to reduce your energy use for transportation.

Drive less

Leaving the car at home when you could walk of ride a bike is perhaps the most obvious way to save energy in our transportation. These options aren’t always possible, due to where we live, the weather, or the seasons, but when it is possible to walk or bike instead of driving huge savings are possible—not to mention the health benefits. The same applies at work; if you’re going out to lunch or need to run an errand, consider providing a little extra time and walking.


Carpooling with another commuter can halve the energy consumption if the two riders live close-by or one rider can be picked up on the drive to work. With three or more riders the savings are even greater. In some places carpooling offers advantages like access to HOV (high-occupancy vehicle) lanes on highways and preferential parking.

Combine trips

When you have to drive, try to combine trips. Schedule your grocery shopping when you’re coming home from work, or run some errands when you have to drive the kids to soccer practice.

Take public transit

Most forms of public transit (busses, light rain, commuter trains) use significantly less fuel per passenger mile than a single-occupancy cars or light trucks. If public transit is an option for you (unfortunately, it often isn’t), take advantage of it. Not only will you save energy and reduce the wear-and-tear on your car, but you’ll also create time to read the newspaper, enjoy a good book, or catch up on e-mail.

Slow down

In a car, wind resistance increases at a cubed function of speed. That means that if you double your highway speed, your power requirements will increase eight-fold (2 cubed equals 8). I’ve experienced this pretty directly. One of our cars—a 2003 Honda Civic Hybrid—has a digital mileage gauge. On a number of occasions I’ve noted my fuel economy driving to the airport (when I’m running late and speeding along at 75 mph) and returning when I can putter along at a leisurely 55 mph. I haven’t done actual calculations to test that cubed function equation, but I’ve seen a dramatic difference: getting a little over 30 mpg at 75 mph, as I recall, and about 50 mpg at 55 mph.

Consumer Reports has examined this issue more thoroughly. The magazine measured the fuel economy of a 2.5-liter, 4-cylinder Toyota Camry driven at 55 mph to be 40.3 mpg, while at 65 mph the fuel economy dropped to 34.9, and driven at 75 mph it dropped to 29.8 mpg—26 percent lower than at 55 mph.

Remove the roof rack

If you’re not using a roof rack regularly, remove it to cut down on wind resistance. Even a fairly modest roof rack can easily cut your fuel economy by a few miles per gallon.

Lighten the load

The more weight we haul around in our cars or trucks, the more energy we use. If you keep sandbags in the bed of your pick-up for winter traction, remove them in the summer. Empty your trunk of those unneeded items you’ve been carrying and never use.

Avoid jack-rabbit starts and stops

With in-town driving, gradual acceleration uses significantly less fuel than pedal-to-the-metal starting and stopping. I try to accelerate as slowly as possible (without inconveniencing oncoming cars) and avoid braking whenever possible as I approach a turn or traffic light. Wayne Gerdes, who coined the term “hypermiling” (a sort-of game to dramatically exceed the rated fuel economy of a car) and who has the website CleanMPG website, recommends driving as if you don’t have working brakes.

Try to avoid coming to a complete stop—within reason

Your car uses a lot more fuel when starting from a complete stop so, when you have a choice, avoid coming totally to rest. When approaching a traffic light that’s red, for example, slow down so that you’re still moving when it turns green. Don’t violate laws or put yourself (or others) at risk in doing so, however. This isn’t a suggestion to roll through stop signs, or slow down so much when approaching a light that the driver behind you will try to swerve pass you.

Avoid idling

If the engine is running and you’re standing still, your fuel economy is zero--and an idling engine usually spews out more pollution than an engine that’s running at higher speeds. Several towns in our area, including Putney, Dummerston, and Brattleboro, now have no-idling resolutions in an effort to discourage the practice. With some vehicles, such as police cruisers and diesel equipment, there may have compelling reasons to keep the engines running, but for cars and light trucks, tuning them off usually makes sense.

Turn off cruise control on hilly terrain

Cruise control is designed to maintain constant speed, but in hilly terrain a lot of extra fuel is used in accelerating up hills. A more fuel-efficient approach is to hold the accelerator pedal in approximately the same position approaching and going over a hill; your speed will drop but fuel economy will be better. On the downhill, allow your speed to increase (within the speed limit), using gravity to boost your fuel economy.

What are your tips?

Most of these strategies are common sense. But that doesn’t mean they always occur to us. Even an energy-efficiency nut like me has to remind myself to follow these practices as I seek to conserve.

What recommendations can you add?

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-01-16 n/a 12336 Making Healthier, Greener Foam Insulation

A proposed change to the residential building code (International Residential Code) would eliminate the need for halogenated flame retardants in many applications

For this Passive House in New York's Hudson River Valley, 12 inches of XPS were installed beneath the concrete slab. With proposed changes to the IRC, subslab insulation wouldn't need to be treated with flame retardants. Click to enlarge.
Photo Credit: Jordan Dentz

As readers of this blog know, I’ve come down fairly hard on certain types of foam insulation over the years. The downsides include the blowing agents used in extruded polystyrene (XPS) and most closed-cell spray polyurethane foam and the flame retardants that are added to all foam-plastic insulation to impart some level of fire resistance.

Now there’s an effort afoot to change building codes in a way that would allow manufacturers to remove the hazardous flame retardants. This is the subject of a just-published feature article in Environmental Building News (log-in required).

This is a significant energy issue, because layers of foam insulation provide the easiest way to achieve the level of energy performance needed to approach net-zero-energy performance. If we’re going to add a lot of foam insulation to our homes, we want that to be safe for the occupants and the environment.

Flame retardants used in foam insulation

We don’t want insulation materials to catch fire, so it is logical to add flame retardant (FR) chemicals to these materials if it will prevent them from catching fire. That’s the reason HBCD (hexabromocyclododecane) is added by all polystyrene insulation and TCPP (Tris (1-chloro-2-propyl) phosphate) is added to most polyisocyanurate and spray polyurethane foam  insulation. These are both halogenated flame retardants—the first using bromine, the second chlorine.

The problem with these halogenated FRs is that they have significant health and environmental risks. The HBCD that is used in all polystyrene (both extruded and expanded) is being targeted for international phase-out by the Stockholm Convention on Persistent Organic Pollutants. It is highly persistent in the environment and bioaccumulative in the food chain; it is believed to cause reproductive, developmental, and neurological impacts. Less is known about the TCPP used in spray polyurethane foam and polyisocyanurate, but there is significant concern in the health and environmental community.

Building codes require that foam-plastic insulation meet a very specific flammability standard. But building codes also require—for most applications—that foam insulation has to be separated from living space by thermal barriers, such as gypsum drywall.

The efficacy of flame retardants compared with thermal barriers

Combustion studies that were done in the 1970s showed that if the insulation is not protected with a thermal barrier, there is no correlation between the presence of FR and the extent of the resultant fire. Thus, the inclusion of a FR does not seem to appreciably increase the fire resistance of foam insulation, according to a peer-reviewed technical paper recently published in the journal Building Research and Information.

However, thermal barriers like half-inch drywall work extremely well at containing fires. The 15-minute protection provided by half-inch drywall gives occupants time to escape a fire. In other words, of the two measures used to impart fire safety to a building assembly (FRs in foam insulation and thermal barriers) almost all of the fire safety benefit is provided by the thermal barrier.

A house under construction in Naperville, IL wrapped in XPS that will be thermally separated from the living area. Click to enlarge.
Photo Credit: Alex Wilson

Changing building codes to allow elimination of flame retardants

Because the vast majority of the fire safety in a building enclosure is provided by the thermal barrier, a group of environmentally aware architects, chemists, and code experts is seeking to change building codes to allow non-FR foam to be used in applications where adequate protection is provided by a thermal barrier. (Disclosure, I have been involved in this initiative.) The code change would allow the FR-free foam to be used below-grade, where the insulation is sandwiched between concrete and earth (hardly a fire risk), and where the foam is separated from the living space by a 15-minute thermal barrier, such as half-inch drywall.

For the former application (below-grade insulation), I believe it’s a no-brainer. Over half of XPS is installed below-grade, so I think there could be a very viable product free of FRs for this application. The change to building codes wouldn’t mandate the elimination of FRs, but it would give manufacturers the option to do so if they chose to. Eliminating the FR for above-grade applications where there is a 15-minute thermal barrier isn’t a slam-dunk, but I believe the case being made is strong.

Changing building codes, however, is a long, challenging process; I don’t know what chances the initiative has. In my article research, manufacturers expressed reservations that they don’t want to have to produce, distribute, and market two different lines of material, and they point out that they also have to be concerned with fire safety of material being stored and during construction (before drywall is installed).

On the other hand, though, foam insulation manufacturers spend a lot to incorporate FRs into their products. The insulation contains a not-insignificant amount of these chemicals: 12.5% TCPP in open-cell spray polyurethane, 4% TCPP is closed-cell spray polyurethane, and 2.5% HBCD in extruded polystyrene. A lot of the strategies for “greening” building products increase the manufacturing costs, while removing expensive FRs should reduce costs. So there is some interest by the industry in this change.

As described in our Environmental Building News article this month, “Getting Flame Retardants Out of Foam Insulation,” the code-change initiative is being targeted, initially, at the International Residential Code. If successful, an effort to change the International Building Code (for commercial buildings) will follow.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-01-08 n/a 12307 What I’m Hoping for in the New Year
An early-morning photo on the West River Trail in Brattleboro. With planned improvements, this will become a great commuting route for bicyclists. Click to enlarge.
Photo Credit: Alex Wilson

A carbon tax, increased awareness of resilience, and more of us leaving the car at home are among my wishes for 2013.

With snow gently falling as the holiday season winds down, I find myself reflecting on the New Year and what we might hope for. World peace of course, and solving the poverty conundrum would be great. But what about energy and the environment? Here are some thoughts:

We will finally put a value on carbon

In mid-2012 the conservative American Enterprise Institute (AEI) made headlines by sponsoring strategic meetings about the merits of a carbon tax. While not fully embracing the idea, AEI seems to be open to carbon taxes—generating ire among their conservative brethren. Also in 2012, former Republican Congressman Bob Inglis of South Carolina, launched an organization promoting carbon taxes, the Energy and Enterprise Initiative.

I have long favored some form of tax on carbon or nonrenewable energy, rather than the more complex cap-and-trade approach that is being tried in a few places, most notably California. As Al Gore said in his 1992 book, Earth in the Balance, we should tax things we want to discourage, like resource consumption and waste generation, and not tax things we want to encourage, like earnings and savings. With elevated concern about climate change generated by Superstorm Sandy, perhaps 2013 will be the year to finally consider sensible ideas like carbon taxes.

More of us will recognize the connection between resilience and sustainability

Following Superstorm Sandy some editorials appeared suggesting that New York City suffered more than it needed to because the focus had been on sustainability or green rather than resilience. I couldn’t disagree more. I believe that the two are inextricably linked—or at least should be linked. Each benefits the other.

The Resilient Design Institute, the nonprofit organization I created in mid-2012, will be working to strengthen this link between sustainability and resilience throughout 2013. I’m excited about that, as I believe that resilience can be the route to far greater buy-in to green building practices (along with sensible urban planning, ecosystem protection, and support for local food production). By the end of 2013 I’m hoping that resilience will be widely understood and increasingly embraced.

Options will become available for low-interest, long-term loans to finance efficiency improvements

The PACE (property-assessed clean energy) program, when rolled out in a few cities between 2008 and 2010, was touted as a key solution to allow more homeowners to affordably finance energy conservation retrofits and renewable energy installations. Loan payments in PACE programs were able to be paid back as part of a homeowner’s property tax bill, and if the house was sold the loan would transfer with the house.

Unfortunately, concern about who’s first in line for payment in the event of a default led to opposition to PACE financing by the loan agencies Fannie Mae and Freddie Mac. Normally, property taxes are superior to debt obligations, and there was concern by lenders that PACE could enable home improvement loans owed to municipalities to be repaid before mortgage obligations to lending institutions.

As this issue is being worked out, residential PACE financing is not available in most places, though there are some exceptions. I’m hopeful that 2013 will see PACE financing—or something like it—become commonplace nationwide.

More utility companies will embrace solar power

Critics point out that photovoltaics (PVs) can’t replace our conventional power generation options. Indeed, it can’t do so alone, but it can be an increasingly important part of a long-term plan to move us toward a carbon-neutral society. Utility companies should look to Green Mountain Power, Vermont’s largest utility company, for progressive policies to expand the implementation of solar.

Small-scale, distributed PV systems will play a key role in achieving Vermont’s Comprehensive Energy Plan, which calls for a shift to 90% reliance on renewable energy sources by the year 2050. Utility companies will play a key role in getting us there.

Leaving the car at home will become cool

Of all the challenges we face in transitioning to a low-energy, low-carbon future, none will be harder than reducing our addiction to the gasoline-powered automobile. One solution to this dependence will be electric and plug-in-hybrid electric vehicles with distributed PV systems charging those car batteries. But we can also make tremendous strides by more actively embracing non-automobile transportation options.

Public transit needs to be a key part of this. Light rail is an option where population density justifies the huge investment. A far-less-costly system, bus rapid transit, was developed in Curitiba, Brazil in the early 1970s and allows low-cost buses to function more like light rail, with passengers quickly boarding from platforms at the floor level of the bus having pre-paid their fares. More than a dozen cities in the U.S. have put bus rapid transit systems in place, and many others are on the drawing boards.

In rural areas like much of Vermont, public transit can consist of smaller buses that travel the major routes on a regular schedule. Making these rural bus systems more viable may depend on increased frequency and employers helping to subsidize the cost.

Making our communities more accessible to pedestrians and bicyclists is also part of the answer. We need to implement traffic-calming measures and build bicycle paths and safer bike lanes on our streets. In my own community, for example, the new West River Trail that extends from the Marina Restaurant in Brattleboro to Rice Farm Road in Dummerston, provides a nice alternative for bicycle commuters in good weather. Maybe 2013 can put us on the path to a future that moves beyond the standard automobile.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2013-01-02 n/a 12301 Changing Behavior and Saving Energy

Turn off the lights, turn down the thermostat, and take shorter showers.

Remembering to turn off the lights is easy and it saves a lot of energy.
Photo Credit: Alex Wilson

We live in a world of gadgets and stuff. When it comes to saving energy, we look to high-efficiency light bulbs or dishwashers. Or we use the advanced weatherstripping to seal our windows or add insulation in our attics. And hopefully we’ll look at fuel-economy ratings when shopping for our next car.

Those are important things to be doing—and we should continue paying attention with all of our purchases. But we should also recognize that behavior is a big part of our overall energy consumption.

The fact is, you can build two identical homes, right next to each other—with the same insulation levels, the same windows, the same appliances, and the same lighting—and the energy bills for those homes can differ by a factor of two, because they are operated differently.

Operating houses in a more energy-efficient manner

So how can homeowners modify the energy performance of their homes? There are lots of ways—many of them so obvious one might be tempted not to even list them. But we sometimes overlook the obvious.

So here’s a starter list—all of them costing nothing. I’m hoping you will comment at the end of this blog with your own suggestions of other ways to reduce home energy consumption based on how you operate your home—or what you recommend to your clients.

In an upcoming column, we’ll take to the road and look at how decisions we make affect our energy use in getting around.

Turn off the lights

As I write this, I notice that we have two kitchen lights on that aren’t really needed. I’m not without guilt when it comes to failing to carry out this obvious energy-saving strategy.

Some of us want to rely on special devices to ensure that we don’t waste lighting energy—occupancy sensors that turn out lights automatically when people leave a room—but we don’t need anything new to make this happen. Creating a culture of paying attention is the easiest solution, and it doesn’t cost anything and doesn’t break down.

Close off unused portions of your home

Reducing the square footage of a home that’s being heated can save a lot of energy. If you have a couple guest rooms that aren’t used on a regular basis, consider closing them off and adjusting your heat distribution system to deliver less heat to those spaces.

With forced-air heat, this involves closing the air-supply register (which results in more warm air delivery to other rooms). If you have hydronic heat (baseboard hot water), there’s usually a long metal flap on baseboard convectors that can be closed to block the release of heat from these units (and keep most of the heat in the hot-water pipe to reach the next room). Neither of these adjustments blocks off all of the heat to these unused rooms—and that’s usually a good thing, as you don’t want to rooms to get too cold—but these adjustments can save a significant amount of energy.

Turn down the heat

How you set your thermostats can have a huge impact on your heating energy use. Set-back and programmable thermostats help with this (and I strongly recommend them), but you can also adjust thermostats manually on a daily basis. A common rule-of-thumb (that may or may not be very accurate) is that for every degree Fahrenheit a thermostat is turned down, savings of 2% in total heating energy use is realized.

So for example, if you keep the house at a constant temperature, reducing the setting from 72°F to 67°F (five degrees) would reduce your heating bill by 10%. Or, a nighttime (8-hour) setback from 72°F to 62°F would reduce your heating bill by about 7% (20% divided by three since the setback is only for eight hours).

Advanced programmable thermostats allow multiple temperature settings during a 24-hour period so that the temperature can be lowered during the day when homeowners are out of the house and again at night when they are sleeping. These thermostats typically allow a different weekend setting. (Note that with radiant floor heating, setback may not be recommended due to the thermal flywheel effect of the concrete slab; get advice from the installer about operation.)

The same setback argument applies in the summer if you use air conditioning—though in reverse. You can save a lot of electricity use for air conditioning by raising your thermostat setting.

Operate storm windows properly

If you have storm windows make sure they’re properly installed in the fall. With triple-track models, make sure the glass panels are properly in their tracks and all the way closed. With old-style wooden storm windows, make sure they’re all back on the windows by the time temperatures drop and ventilation is no longer needed. To simplify the seasonal adjustments with our wooden storm windows, we only remove the storms from those windows we use for ventilation. The other storm windows stay up all year.

Take shorter showers

Heating water is often the second-largest energy use in a home, and in a highly insulated home it’s not uncommon for it to be number-one. Our largest use of hot water is often showering, so by taking shorter showers significant savings can be realized. No big surprise there.

Another showering habit that will save energy is to reduce the flow when shampooing or shaving. For this reason, I prefer shower valves that have separate controls for both temperature and volume so that the flow can be adjusted without affecting the temperature mix. If you have a single lever that controls only the temperature, you can install a showerhead with a cut-off valve that reduces the flow to a trickle, or a valve that’s installed between the stem and showerhead.

Wash clothes with cold water

Another simple and fairly obvious strategy for saving energy is to switch to cold-water washing. We’ve been washing most of our clothes in cold water for several years now, though we still use hot or warm for certain loads. Use a detergent optimized for cold-water washing.

You can also save energy by hanging clothes outside. Some people I know line-dry their laundry, but then put in the dryer for a few minutes to fluff it and remove the stiffness from outdoor drying.

Operate your dishwasher with full loads

Dishwashers consume energy both by using hot water and from the heated drying cycle. If you use the dishwasher less frequently by only running it when it’s all the way full, you’ll save energy. You can also turn off the electric-heat dry function. With the several dishwashers my wife and I have owned over the past 30 years I don’t think we’ve ever used the electric drying option.

Other no-cost ways to save energy

I’ve provided here just a few examples of simple ways to save energy in our homes simply by changing the way we do things. There are lots of other examples having to do with cooking, refrigerators, how we dress, and using fans instead of air conditioning. What are your favorite strategies?

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-12-20 n/a 12289 A Christmas Shopping List

A few shopping ideas for the holiday season.

A Yuba cargo bike with precious cargo.
Photo Credit: Yuba

I’m not a big shopper. I don’t even particularly like getting presents. Our society is just too much about consumption. Nonetheless, as I’ve done on occasion in the past, I’m providing below some Christmas shopping ideas.

1. LED light bulb

Every time I turn around, it seems, I see another LED light bulb. Among the screw-in replacement lamps, there are many good products—but also some that aren’t so good. Look for products from a reputable manufacturer (a company that’s been around for a while), and select a product that carries an Energy Star label. The most common problem with LED lamps is failure due to poor heat management; I’ve had products fail after less than a year.

My latest LED lamp purchase—a Philips EnduraLED 12.5-watt lamp that replaces a 60-watt incandescent light bulb—seems like a real winner. It sells for about $25, but you will sometimes find them on sale for less.

For a selection of recommended LED light bulbs, check out the LED replacement bulb section in GreenSpec.

2. Kill-a-Watt Meter

This has been on my Christmas list before. It’s a gadget that lets you measure the electrical consumption of plug-in appliances, equipment, and other devices. It can help us sleuth out hidden stand-by (phantom or vampire) losses—the power draw from a television that’s turned off or a WiFi router that’s on 24-7. I have several Kill-a-Watt Meters and regularly loan them to friends. The cost is about $20. Note that it doesn’t work for hard-wired appliances like most dishwashers or 220-volt products.

See Kill-a-Watt in GreenSpec.

3. Smart power strip

Along with measuring the phantom electric loads from televisions and stereo equipment, you can do something about it by installing a smart power strip that turns off selected circuits either based on an occupancy sensor that knows no one is present or after a period of inactivity, as indicated by lower current draw (say from a DVD player). There are a number of these devices on the market. I just bought a TrickleStar power strip at a sale price of $25. There’s also the SmartStrip LCG3, the Take Charge Power Saver Smart Strip, the Belkin Conserve Socket, and the WattStopper Isolé Power Strip with Personal Sensor—to mention a few. These products also include surge protection.

For more outlet control products, check out GreenSpec.

4. Electroluminescent night light

When I covered these little devices before there was just one company making them: LimeLite Technologies. Today there are at least several others. These plug-in night lights use only trickle of electricity (about 2¢ worth per year, according to LimeLite), but provide a soft glow at night (a photosensor turns it off in the daytime). Cost is about $5, though you may find them sold in two packs for not much more. Lots of companies buy them in bulk, printed with their logos and give them away as premiums.

5. Low-flow showerhead

I know, it sounds boring, but a pleasing shower that saves water means money in the pocket. Expect to spend about $25 for a really good 1.5 gallon-per-minute showerhead. I’ve used a Delta H2Okinetic model for five or six years in our rural home with low (and fluctuating) water pressure. It delivers just 1.5 gpm at 60 psi—I measured about 1.4 gpm at our house, and we love it. Delta reengineered the showerhead to produce large drops (that retain heat) and deliver them at high pressure.

GreenSpec has a broad selection of low-flow showerheads.

6. Programmable thermostat

For people with standard gas- or oil-fired forced-air or hydronic heat, a properly operated programmable thermostat can save hundreds of dollars of energy per year. The key here is “properly operated.” Studies have shown that most programmable thermostats don’t save energy because the homeowners don’t know how to use them. Take the time to figure it out, and program it properly. A few minutes of set-up could buy several elegant dinners per year. Typical costs are $50 to $100.

7. Smart phone app that encourages you to walk more

I don’t have one of these apps, but I have some friends who use them religiously, and the devices have changed their lives by encouraging them to walk more. I guess for some people that competitive drive—how many miles did I walk this week?—makes a huge difference. And if that what makes the difference, go for it. These apps use GPS features of smart phones to measure how far you’ve walked, run, or bicycled, including elevation gain, etc., as long as you have the phone on your belt or in your pocket. Among the leading apps for iPhone are MapMyWalk, Pedometer PRO, Walkmeter, RunKeeper…. There are dozens, if not hundreds for iPhone and Android phones. Most cost a few dollars or are free—though I suspect the free ones remind you about upgrades with annoying frequency.

8. Public transit passes

As an easy gift to employees that helps the planet, not much beats transit passes—as long as there’s a public transit option where the passes can be used. When I’ve lived in a place where I could use public transit regularly, I loved the chance to read the paper (today it would probably be an iPad), avoid traffic congestion, and skip the parking hassle.

9. Cargo bike

Cargo bikes are cool. I love the idea of being able to use a bike to haul groceries, pick up kids at school, even help your friends move. There has been a veritable explosion of interest in cargo bikes, with more than a dozen manufacturers now offering them in the U.S. As with a lot of cool stuff, the modern incarnation of this trend came here Europe—especially Holland and Denmark. But a sizeable player remains Worksman Cycles in the Queens, New York—the oldest continually operating bicycle manufacturer in the country (founded in 1898, during the first utility bike boom).

Brattleboro’s Specialized Sports recently started carrying Yuba cargo bikes, and a recent transplant to town, Dave Cohen, helped to launch the cargo bike revolution in Berkeley in the early 1990s, when he started the worker cooperative Ped-Ex (later to change its name to Pedal Express when threatened with a lawsuit from another delivery company with a similar-sounding name that must have been worried about losing business to the bikes.) A lot of carbo bikes, including Yuba products, are available with battery-powered electric booster motors.

10. Donate to a good cause in the name of friends and family

The final gift idea is not a product at all, but rather donating to a cause that will give you and the recipients of your generosity a sense of satisfaction. There are thousands of good causes related to energy and the environment—from national organizations like the Rocky Mountain Institute, to regional groups like the Northeast Sustainable Energy Association, to local initiatives like Windham and Windsor Housing Trust and Co-op Power of Southern Vermont.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.



2012-12-12 n/a 12274 Open-web rafters for superinsulated roofs

Open-web, parallel-chord joists with solid-wood diagonal struts for use as superinsulated roof rafters.

Open Joist Triforce rafters being installed on our house. Click to enlarge.
Photo Credit: Alex Wilson

Last week I wrote about an innovative foundation insulation material, Foamglas, that we used in our new house in Dummerston. This week I’ll talk about the open-web rafters we’re using to achieve a superinsulated roof.

First, a little background. To create highly insulated roofs there are several approaches:

When the insulation is installed in the attic floor (creating an unheated attic), it’s easy to obtain very high R-values inexpensively—it’s cheap, that is, as long as you don’t count the cost of the lost living space by creating an unheated attic. Basically, you just dump in a lot of loose-fill cellulose or fiberglass on the attic floor, filling the joist cavity and more.

I’ve heard of as much as two feet of cellulose insulation being installed in this manner, achieving about R-80. To make room for a lot of insulation at the roof eaves, it’s usually necessary to install “raised-heel” trusses for the roof framing (so that the insulation thickness at the edges is not significantly compromised.

The Triforce joists are made with solid-wood diagonal struts and glued, finger-jointed connections. Click to enlarge.
Photo Credit: Alex Wilson

If you want to insulate the sloped roof, creating living space—as we are doing—you can either install very thick rafters (14 inches or more) that can be filled with cavity-fill insulation, or you can provide more modest roof trusses or rafters and then add a layer of rigid insulation on top of the roof sheathing. An advantage of the latter approach is that the layer of rigid insulation controls the “thermal bridging” through the rafters or top chords of the roof trusses.

To keep the insulation costs down and minimize our use of foam-plastic insulation, we opted for the former option—putting all our insulation in the rafter cavities rather than installing a second layer of outboard insulation.

Finding deep-enough rafters

To achieve the 16-inch depth we wanted for insulation and an air space under the sheathing, we used open-web, parallel-chord trusses as the rafters. These trusses, typically used as joists, have diagonal bracing or “struts” and are made by in Quebec by Open Joist Triforce.

Unlike most parallel-chord trusses, Tri-Force uses solid wood, rather than OSB, and finger-jointed glue joints rather than metal truss plates for attaching chords and webs. Some experts are concerned about the long-term durability of OSB webs in more common I-joists and the metal fasteners in standard roof trusses.

The chords on Triforce joists are either 2x3s or 2x4s, and the diagonal struts are solid-wood 2x2s. Connections between the struts and chords are achieved with precision-machined grooves and polyurethane adhesive. The wood is all northern, slow-grown spruce, rather than plantation-grown southern yellow pine or poplar.

Detail showing finger-jointed glue joint. Click to enlarge.
Photo Credit: Alex Wilson

Triforce joists include a section of OSB at the ends so that the length can be adjusted. This permits manufacturing in standard lengths and keeps the costs down.

Providing a stem wall and roof overhang

In our case, to expand the living area in the upstairs of our compact house, Eli Gould added “raised heels” to the roof trusses. The OSB tails on the Triforce rafters made this fairly straight-forward, though it certainly involved some additional labor. The design at the roof eaves also provides for nearly two feet of roof overhang—a high priority in keeping moisture off the wall and away from windows and foundation.

Despite the extra work with the raised-heel and overhang, the rafters went up quickly. Eli’s crew worked all-day on the Saturday before Superstorm Sandy came through to get the roof up and sheathed with Huber’s Zip sheathing (with joints taped). They were able to keep everything remarkably dry.

Insulation options

We have not made a final decision about the type of insulation we will use for the roof. We are deciding between dense-pack cellulose and acrylic-stabilized, blown-in fiberglass (probably Johns Manville Spider). With 14 inches of insulation, the difference in weight between cellulose (at about three pounds per cubic foot) and Spider (1.8 pounds per cubic foot) is significant.

With either material, we believe that by stapling up mesh-fabric baffle on each rafter we will be able to fill each rafter cavity completely—including all the corners where the diagonal struts intersect the chords. The small amount of acrylic adhesive in the JM Spider product may prove to be a significant benefit to us in fully sealing the cavities—so we’re leaning in that direction.

We think the fabric will help us achieve complete filling of the rafter cavity with fiber insulation. Click to enlarge.
Photo Credit: Alex Wilson

The two materials provide similar insulation values: about R-4.1 to 4.2 per inch for the JM Spider fiberglass and about R-3.7 per inch for dense-pack cellulose. With 14 inches of insulation, that would come to about R-58 with JM Spider, vs. R-52 with dense-pack cellulose.

From an environmental standpoint, cellulose has higher recycled content (about 80% recycled newspaper), though fiberglass insulation is now made using a significant amount of recycled glass (mostly from beverage containers). Johns Manville fiberglass is certified to have minimum 25% recycled glass content (with 80% of that recycled content being post-consumer).

Flame retardants are not required in the fiberglass, while borate and ammonium sulfate flame retardants are used in cellulose.

Here's the product listing in our GreenSpec database.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.



2012-12-04 n/a 12224 Gaining Experience with a New Material

Using Foamglas instead of polystyrene to insulate beneath our basement slab and on the foundation walls.

Eli Gould cutting Foamglas for use under our basement slab. Click to enlarge.
Photo Credit: Alex Wilson

In my role with Environmental Building News and our GreenSpec Product Database, I get plenty of opportunity to research and write about innovative building products. That’s one of the really fun aspects of my job.

On occasion I also get an opportunity to try out new or little-known materials. In the construction of our new home in Dummerston, Vermont—actually the rebuilding of a 200-year Cape—I’ve had opportunity to get some real experience with lots of products. One of these is a cellular glass insulation material known as Foamglas (check out Foamglas in GreenSpec).

Why we need a product like Foamglas

I’ve written often about the problems with extruded polystyrene from an environmental and health perspective. Relative to performance, extruded polystyrene (XPS) is a great product. It is water-resistant so can be used below-grade; it has high compressive strength so can be used beneath a concrete slab floor; it insulates very well (R-5 per inch); and it’s inexpensive. These properties make XPS the nearly universal choice for sub-slab and exterior foundation insulation today.

We installed 4"-thick Foamglas as sub-slab insulation. Click to enlarge.
Photo Credit: Alex Wilson

But along with these benefits are some significant downsides. All XPS today (as well as expanded polystyrene, EPS) is made with the brominated flame retardant HBCD that has recently been added to the Stockholm list of Persistent Organic Pollutants (POPs) and is being banned in much of the world. HBCD provides some level of fire protection, though some studies suggest that its benefits are greatly exaggerated—and that that protection, if real, is irrelevant below grade.

In addition, XPS is currently made with the blowing agent HFC-134a, which is a potent greenhouse gas that contributes to global warming. And some of the petrochemical-derived raw materials, including benzene and styrene monomer, are carcinogenic—though once converted into polystyrene, that carcinogenicity is not present.

From a performance standpoint, XPS—like most other foam plastic insulation materials—is readily tunneled through by subterranean termites, carpenter ants, and other wood-boring insects.

In this photo you can sort-of see the cellular structure of the rigid material. Click to enlarge.
Photo Credit: Alex Wilson

Foamglas to the rescue

Foamglas is a cellular glass, rigid boardstock insulation material. It has high compressive strength, excellent moisture resistance, and tremendous fire resistance without the use of flame retardants. It is moderately well-insulating at R-3.4 per inch (32% lower than XPS), and it’s made without environmentally damaging blowing agents. It is also about the only insulation material that is totally impervious to wood-boring insects—a useful property for below-grade applications—particularly in a warming planet with termites extending their ranges north.

Foamglas has actually been around a long time—since Pittsburgh Corning introduced it in the 1930s—but it is used primarily for high-temperature industrial applications, such as insulating steam pipes and furnaces. It’s use as an insulation material for buildings remains very uncommon, though this use is increasing in Europe.

Even though Foamglas is significantly more expensive than XPS and its per-inch insulating value is lower, the environmental and health benefits made me want to try it out on our own home.

We installed 6" Foamglas blocks on the exterior foundation walls using a polymer-cement adhesive. Click to enlarge.
Photo Credit: Alex Wilson

Our use of Foamglas

We installed four inches of Foamglas under the basement floor slab and six inches on the exterior of the foundation walls. Our designer/builder, Eli Gould, and his six-person crew not only did admirably with this little-known material, but he came up with what I believe is a great option for adhering Foamglas to a foundation wall.

We were debating whether to use Pittsburgh Corning’s recommended solvent-based adhesive (“tar”) or their acrylic formula (a greener, water-based tar), which apparently doesn’t have quite as good performance properties as the solvent-based option. But the recommended solvent-based formulation sounded quite hazardous (it’s a two-component adhesive with one component consisting of three different types of diisocyanate and the other component consisting of petroleum asphalt, coal bitumen, naphthenic distillate, and hydrocarbon solvents). We wanted a well-performing adhesive, but the solvent-based option didn’t sound like something we wanted to expose workers to during installation or surround our home with. 

Eli tested different engineered cement products, as modern polymers have dramatically changed the adhesive capabilities of cement in the last couple decades. They are also free of VOCs and sounded far safer from a health and environmental standpoint.

Mixing the Ardicoat waterproofing material—an acrylic gets mixed with a proprietary mix of Type I and Type II portland cement.
Photo Credit: Alex Wilson

We settled on a polymer cement product  made by Ardex used for adhering stone veneer onto masonry walls, and it worked beautifully. The two companies (Ardex and Pittsburgh Corning) were so intrigued by our field-testing that they have begun conversations about testing and developing this alternative adhesive system.

Ardex also supplies a waterproofing coating that we applied over the Foamglas on the foundation walls: Ardicoat Plus. We used this in place of conventional asphalt-based (tar) coating, and I feel really good about not having hydrocarbons from the coating seeping into the groundwater or being released as VOCs.

Innovation and performance

Our foundation ends up with a respectable R-12 under the basement slab and R-22 on the exterior of the foundation walls. That’s not up to Passive House standards, but it should be good enough to enable us to achieve net-zero-energy performance with a PV system supplying power for an air-source heat pump. And it should last literally hundreds of years—a lifespan that I believe we should be aiming for in home building today.

We spent more for the Foamglas foundation insulation than we would have with XPS, but it feels good to have put my money where my mouth is relative to spurring product innovation and demonstrating greener building material options.

Eli and I also hope that by leading this sort of collaboration we may be able to help drive down the costs while broadening the market for Foamglas and other innovative products. With Foamglas and other inorganic products like this that may come along, we hope to see more durable, insect-resistant foundation systems that can help reduce energy consumption while minimizing health and environmental impacts.  

A layer of polypropylene mesh gets embedded into the Ardicoat for strength and flexibility.
Photo Credit: Alex Wilson

Foundations are not the only part of the building in which Eli and I plan to help companies “connect the dots” in developing better buildings. We’re working on innovative window solutions for existing homes, superinsulated roof systems, and modular components to speed construction—but those are topics for future columns.

Who knows, maybe we can even convince some leading manufacturers to move to the Brattleboro area and help to spur economic development in the region.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-11-29 n/a 12213 A Few Product Highlights from Greenbuild

The Greenbuild conference, as usual, was the place to find out about innovations in green building products.

Agepan THD wood-fiber insulative sheathing is now being sold by the Small Planet Workshop. Click to enlarge.
Photo Credit: Small Planet Workshop

I attended the Greenbuild Conference and related meetings in San Francisco last week. This is the largest conference and trade show in the green building field, and it is increasingly becoming the national event where large manufacturers roll out new building products.

Described below are a few product highlights from the trade show that caught my eye as I wandered around. I only got through about a quarter of the trade show.

Wood-fiber insulation from Germany

In Europe it is becoming increasingly common to use high-permeability wood fiber sheathing as an exterior insulation material, and at least one such material was on display at the conference. The Small Planet Workshop in Olympia, Washington, is now distributing the German product Agepan THD. These 2"-thick panels insulate to R-5.7 (R-2.3 per inch) and have a high perm rating of 18—meaning that water vapor can pass through it fairly easily.

It’s hard to say whether wood-fiber insulative sheathing will gain followers here, but there is growing interest in wall assemblies that won’t trap moisture, so products like these are worth keeping an eye on. The Small Planet Workshop also distributes the expanded-cork boardstock insulation that I’ve written about previously and that I’m planning to use on my own house in Dummerston, Vermont.

Vacuum insulation moving into the main stream?

Vacuum insulation has been around for a while, but it has never made inroads into the market—despite a major effort for Owens Corning to do so with its Aura panel way back in 1992. Dow Corning is going to give it a shot. After premiering its Vacuum Insulation Panel (VIP) at the Living Future Conference in May of this year (see BuildingGreen article and GreenSpec product page), the company made a bigger splash at Greenbuild.

Dow Corning’s VIP is sold in 24" by 36" panels in thicknesses from a quarter-inch to an inch-and-a-half. The panels have a fumed silica core that is 95% pre-consumer recycled content, wrapped with an aluminum skin, and 1"-thick panels provide an insulating value of R-39 (center-of-panel).

Dow Corning’s vacuum panel is being specified in commercial-building facades to insulate spandrel glass (in all-glass curtainwall buildings, the opaque glass that spans between glazing), but I believe the primary application for VIPs will be in appliance manufacturing where high insulation performance in thin layers is desired (refrigerators, freezers, and water heaters). A press release on the product with a link to a downloadable information sheet is found at this link.

A high-R-value coating with silica aerogel

Silica aerogel is a bizarre material. Aerogel the lowest-density solid known. It transmits light and insulates extremely well, owing to its molecular structure. For the past decade, the Cabot Corporation has produced silica aerogel granules under the brand name Lumira (previously Nanogel) that are used in daylighting panels that provide diffused light even while offering remarkably high insulating value (about R-20 in a 2-1/2" panel), and the material is also incorporated into a felt-like mat that can be used in roofing fabrics. Find Lumira in GreenSpec here.

At Greenbuild the company introduced a new formulation of silica aerogel, Enova, that can be added to paint to provide a thin, insulating coating. A very effective demonstration in the booth used a piece of aluminum that was half painted with this 2 mm-thick coating and half uncoated with a refrigerated space behind. You could feel the dramatic difference in temperature, since the aerogel coating significantly reduced heat flow through the material. A key benefit will be preventing condensation.

Zehnder’s top-efficiency HRV now certified by the Home Ventilating Institute

Zehnder is Swiss manufacturer of high-efficiency heat-recovery ventilators (HRVs) for whole-house ventilation. Represented in the U.S. by Zehnder America since 2010, the company is defining the future of high-performance ventilation. All of the company’s HRVs carry Passivhaus certification, and the company’s Novus 300 HRV recently earned certification with the Home Ventilating Institute (HVI).

Based on the HVI test methods, the Novus 300 achieves “apparent sensible effectiveness” of 94% to 96% and “sensible recovery efficiency” of 90% to 91%, significantly exceeding the performance of any other HRVs in the HVI Certified Products Directory. One of the company’s ComfoAir models (see GreenSpec product page) also carries HVI certification, and others in the line will be certified.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-11-19 n/a 12208 Comparing Fuel Costs

An easy-to-use online Fuel Cost Calculators lets you compare different fuels in terms of today’s energy costs.

BuildingGreen's online Fuel Cost Calculator—shown here with current Vermont costs for heating oil and electricity and assumptions on how those energy sources are used. Click to enlarge.
Photo Credit: BuildingGreen, Inc.

If there’s one thing that we can predict with certainty about fuel costs, it’s that they fluctuate a lot. That wasn’t always the case. The price of electricity, natural gas, propane, and heating oil were remarkably stable for decades—up until the 1970s.

Since then, prices of most fuels have gyrated wildly, driven by political unrest in some parts of the world, periods of greater or lower demand driven by periods of strong economic growth or contraction, resource limitations (real or perceived), and the situation in China and other parts of this increasingly connected world.

With regulated energy sources (particularly electricity), there is often less volatility, because regulators have to approve changes in pricing.

What does this mean for you as you compare one heating option to another or try to figure out whether to buy a pellet stove this winter? How does oil compare with propane or electricity as a heating source? Those sound like simple enough questions, but it’s actually fairly complicated.

For starters, different fuels are sold in different units. Heating oil, kerosene, and propane are sold by the gallon; natural gas by the hundred cubic foot (ccf) or therm (defined as 100,000 Btus); firewood by the cord; wood pellets and coal by the ton; and electricity by the kilowatt-hour (kWh).

Second, different fuels have different energy densities. According to The Engineering Toolbox (a great source of facts related to energy), a gallon of propane contains 91,330 Btus, while a gallon a #2 heating oil contains 139,600 Btus. Pellets contain 16.5 million Btus per ton, and natural gas contains 950 to 1,150 Btu per cubic foot.

Third, the amount of useful heat obtained from a given fuel depends on how efficiently it’s burned. Combustion efficiency varies widely—from as low as 30% for the worst of the outdoor wood boilers to over 95% for a top-efficiency, condensing gas boiler. Baseboard electric-resistance heat is 100% efficient—since the electrons you’re paying for in the electric current are converted entirely into heat, while heat pumps typically deliver two to three units of heat energy for every unit of electric energy consumed (these can be thought of as 200% to 300% efficiency, though it’s really a coefficient of performance, not efficiency). Note that these electric heat efficiencies don’t account for the “upstream” energy costs of electricity generation, such as the waste heat at a coal or nuclear power plant—but for the purposes of comparing your heating costs, that doesn’t matter.

To further complicate fuel cost comparisons, a fourth factor is how efficiently heat is distributed. With electric baseboard radiators, the heat is produced right in the room, so the distribution is 100% efficient. Baseboard hot water (hydronic) heat is also usually very efficient, though uninsulated hot water pipes running through an unheated basement can lower that efficiency to some extent. With a forced-air furnace and ducts to carry the heat, however, the distribution efficiency can be quite low, especially if poorly insulated, leaky ducts run through an unheated attic or crawl space—distribution efficiency as low as 50% is not uncommon.

To calculate the actual delivered efficiency of your heating system, you have to multiply the heat content of the fuel by the combustion efficiency and by the distribution efficiency. For example, if you have a 78% efficient propane furnace and an average duct system running through an unheated attic (65% efficient distribution), your overall efficiency of delivered heat is just over 50% (.78 x .65)—meaning that only half of the energy you’ve paid for is actually being used to keep you warm!

Finally, to compare different fuels (sold, as described above, in different units), you have to convert the costs to an equal basis so you’re comparing apples to apples. The most common standard is dollars per million Btus of delivered heat. The easiest way to do this is with an online calculator like the Heating Fuel Cost Calculator our company provides.

This allows you to enter the cost for a particular fuel, your heating system efficiency, and its distribution efficiency. The end result is a figure in dollars per million Btu that reflects your real costs of delivered heat and allows you to compare that with other options. Say you heat with oil and pay $3.77 per gallon (the average retail price in Vermont last week), using an Energy Star boiler (83% efficient) and hot water baseboard distribution (98% efficient). Your cost of delivered heat with these assumptions will be $33.42 per million Btu.

By comparison, electric baseboard heat at the current Green Mountain Power rate of 16.9¢/kWh converts to $49.53 per million Btu of delivered heat—that’s 48% higher than the oil option above. Using a heat pump with a coefficient of performance of 2.25 (225% efficient) and ducts fully within the insulated house envelope drops the cost of delivered heat to $22.46 per million Btu (33% less that the oil-heat option). And firewood, at $250/cord burned in an EPA-compliant wood stove (70% efficient), converts to just $16.23 per million Btu of delivered heat (see image). The beauty of an online calculator is that you can quickly and easily vary any of the inputs to compare lots of fuels and heating options.

Keep in mind that energy costs are volatile. It doesn’t make sense to replace an oil boiler with a propane boiler based only on the heating cost savings given today’s rates, since they could change dramatically tomorrow. But if you’re thinking about replacing equipment anyway, you should consider the fuel costs of the alternatives.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-11-15 n/a 12188 Gas Lines Point to a Need for Resilience

Hurricane Sandy demonstrated the vulnerability of our dependence on automobiles; we need to become a lot more resilient.

Gas line in Woodbridge, New Jersey on November 1st. Click to enlarge.
Photo Credit: AP

By now we’ve all seen the photos of houses buried in sand along the Jersey Shore, burned-out homes in Queens, and submerged subway stations in Manhattan. Those spectacular images were in the first wave of news from Superstorm Sandy last week.

The secondary, lingering effects might not be as dramatic, but they are nonetheless highly significant. And they demonstrate, ever so clearly, our need for greater resilience. As of late-afternoon Sunday, November 4th, there were still 1.8 million customers without power, the vast majority of them in New York and New Jersey. That’s down from 8.5 million without power at the peak, but it still includes almost a quarter of New Jersey. In some places outages may last for weeks.

Outages in August in New Jersey aren’t so bad—there might be some discomfort from the heat, but few at real risk of safety—but with temperatures dropping into the 30s early this week, power outages become quite serious. The vast majority of our heating systems require electricity to operate—for the fans, pumps, and controls—though there are some exceptions.

Gas lines have become a traffic hazard in New Jersey and Long Island in the aftermath of Superstorm Sandy.
Photo Credit: Sean Malone

Power outages and gas stations

Along with these obvious problems of power outages—lack of lighting, heat, and appliances—power outages affect us outside the home as well.

As we learned in New Jersey and Long Island, without power most gas stations can’t operate. The American Automobile Association estimated on Thursday, November 1st, that 60% of service stations in New Jersey and 70% on Long Island were closed because they don’t have power to pump fuel. Only 23% of New Jersey service stations were still without power by Sunday morning, but lines persisted in many areas.

There were also actual fuel shortages, which contributed to the problems. The U.S. Department of Energy reported that 13 of the region’s 33 fuel terminals were closed as a result of the storm, along with two major gasoline pipelines serving the area.

Without gasoline, we can’t run our cars. But those shortages also meant that homeowners with smaller, gasoline-powered generators were running out of fuel.

Moving toward resilience

The solutions to these problems are many-faceted. Relative to the need for generators, we should build greater resilience into our homes. All homes should be able to maintain livable conditions in the event of loss of power or heating fuel. This is a familiar refrain of mine.

We can do this with much better building envelopes (significantly higher insulation levels, triple-glazed windows, tighter construction) and passive solar gain. With such features, the temperatures in those homes should never drop below 45 or 50 degrees Fahrenheit, even in the middle of winter if there’s no power and our heating systems can’t operate.

People waiting to fill gas cans to fuel their generators at a gas station in Madison Park, New Jersey on October 31st.
Photo Credit: Lucas Jackson, Reuters

A mobile generator and battery bank

With the net-zero-energy house my wife and I are currently building (rebuilding) in Dummerston, Vermont, we’re thinking of installing a fairly conventional grid-connected solar-electric (PV) system, but using a new inverter that is coming out early next year that allows you to plug a load into it when the sun is shining—even when the grid is down. (Most grid-connected PV systems can’t operate when the grid is down, though the sun may be shining brightly.)

Rather than a battery bank for back-up electricity during power outages, we’re thinking of using the plug-in hybrid car we plan to buy for most of our emergency power needs. It will have a battery system (which we’ll normally charge using electricity from our PV array), so why install a second battery system that will only get used during occasional power outages. Our car can be our resilient power system.

Reducing dependence on cars

Relative to gasoline shortages and the inability to pump gas during outages, we can achieve greater resilience by reducing our dependence on the automobile. This isn’t a quick fix, but through involvement in local planning efforts and by influencing transportation funding priorities, we can produce more pedestrian-friendly spaces that allow people to reach key services safely on foot or by bicycle.

If we create communities that can function reasonably well without automobiles during times of emergencies, those will be places where automobile use may also drop during normal times. These will be cleaner, safer, healthier places that move us toward sustainability.

Final thoughts

Resilient design is about all of this. It is an integrated process that will keep us safer and allow us to bounce back more quickly from whatever the next disturbance might be.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-11-07 n/a 12179 Masonry Heaters

One of the cleanest and most efficient ways to burn wood is provided by high-mass masonry heaters.

A Tulikivi masonry heater made of soapstone with an integral bake oven and bench.
Photo Credit: Tulikivi

Over the past two weeks I’ve written about wood stoves and pellet heating. This week I’ll focus on another way to burn wood cleanly and efficiently: using a masonry heater.

A masonry heater, also called a masonry stove or Russian fireplace, is a wood-fired heating system that is fired intermittently at very high temperature to heat up the large quantity of thermal mass, which then radiates heat into the home. The heater has a circuitous path through which the flue gasses flow. Here, the heat is transferred to the stone, brick or other masonry elements of the heater.

Key benefits of masonry heaters

From an environmental standpoint, masonry heaters burn fuel very rapidly at a high temperature. This results in very complete combustion with little pollution generated. Except when first starting the fire, there should be no visible smoke.

From a performance and comfort standpoint, masonry heaters take a long time to heat up, but they then continue radiating heat for a very long period of time, typically 18 to 24 hours. The outer surface of a masonry stove never gets as hot as a cast-iron or steel wood stove, but it retains its heat much longer. The surface area provides a large radiant surface, contributing to comfort.

Operation of masonry heaters

Unlike a wood stove, where you typically start a fire and then keep it going for a long period of time by adding fuel, with a masonry heater you operate it in batches, and the fuel is typically entirely burned by the time the next fire is started. This means that you have to start a lot of fires—which some people will find less convenient.

Because the firebox may not be very large in a masonry heater and because a fast-burning, intense fire is desired, the firewood is cut and split differently. Often the length of acceptable firewood is less than with a wood stove (sometimes as short as 12 inches), and the optimal diameter of split wood is smaller—typically 3-5 inches.

A custom masonry heater built by William Davenport using granite and marble.
Photo Credit: Masonry Heater Association of North America

Because the heat from a masonry heater won’t warm up a space quickly (it may take several hours for the outer surface to reach peak temperature and peak heat delivery), it isn’t as effective as a wood stove at quickly taking the chill off. You need to plan ahead. And if it’s going to be a sunny autumn day and you have a lot of south-facing windows, starting the masonry heater in the morning may result in a period of overheating later in the day when the solar gain peaks.

Some masonry heaters include bake ovens or warming areas built into the modules, offering a nice feature for those interested in wood-fired baking. Others include integral benches for seating.

Product options

Masonry heaters are often custom-built, and such units can satisfy a wide range of design needs and special requirements. Because they are large and heavy, provision must be made for such units—such as a concrete slab or concrete bearing walls beneath the heater. The Masonry Heater Association of North America is an excellent resource on masonry heaters and includes a directory of masonry heater builders.

There are also some manufacturers of modular masonry heaters that can be assembled relatively easily. The best-known manufacturer is the Finnish company Tulikivi . Tulikivi heaters are made from soapstone or ceramic and are available in a wide variety of styles, both with and without bake ovens. Some include integral bench seats.

If a house has the space for it, a masonry heater is often the best way to heat with wood. In new construction, particularly in rural areas, it’s definitely worth looking into. Find the more efficient and less emitting masonry stoves in the masonry heater section in GreenSpec.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.


2012-11-01 n/a 12139 Heating With Wood Pellets

What to like and what not to like about pellet stoves and pellet boilers.

Our Quadrafire pellet stove, which we can operate even during a power outage. Click to enlarge.
Photo Credit: Alex Wilson

We have a sort-of love-hate relationship with our pellet stove. My wife leans more toward the latter, while I see the benefits outweighing the negatives. In this column I’ll outline the primary advantages and disadvantages of pellet heating.

Advantages of wood pellet heating

Regional fuel. The fuel is—or can be—local or regional in origin. At a minimum it’s not fuel that’s coming from places where they don’t like us—like the Middle East. When I’m buying pellets, the source is a significant consideration. I’m willing to pay slightly more to have my pellets come from nearby plants in Jaffrey, New Hampshire or Rutland, Vermont.

Carbon-neutral. The life-cycle of wood pellet production and use can—and should—be close to carbon-neutral. With natural gas, propane, or heating oil we’re taking carbon that was sequestered underground millions of years ago and releasing that as a greenhouse gas into the atmosphere (where it contributes to global warming). When we burn wood pellets we’re still releasing about the same amount of stored carbon into the atmosphere, but that carbon was sequestered in the wood fiber over just a few decades, and if we’re managing our woodlands properly (replacing harvested trees with new ones) the entire life cycle results in almost no net carbon emissions.

Relatively clean-burning. Wood pellets are a lot cleaner-burning than cordwood. This is because pellet combustion is aided by a fan that supplies a steady stream of air to the burn pot. When I first start up my pellet stove—as the electric heating element heats up the pellets to start the combustion—there’s some smoke produced, but once the pellet stove is operating there is no visible smoke being generated. (This is a reason to set the temperature differential on the control relatively high—so that it won’t cycle on and off too frequently.)

Infrequent stoking. Pellet stoves have integral bins that can be filled every few days in cold weather, and most pellet boilers have stand-alone bins that hold several months’ worth of pellets. Regular stoking isn’t required—unlike with a wood stove. If a pellet stove is your only heating system in a space (as is the case with our apartment) how long you can go away depends on the energy efficiency of the building, expected outdoor temperatures, the volume of pellets your stove or bin holds, and the thermostat settings. With our pellet stove, we can go away for about three days in the coldest Vermont weather as long as I leave the thermostat set fairly low.

Convenient. With a pellet stove you don’t have to handle firewood. I’m sure I’ve cut, split, stacked, and burned a couple hundred cords of wood over the decades, and I know that it’s a lot of work. With pellet stoves you’re still handling the fuel—usually 40-pound bags of the rabbit-food-size pellets—but it’s more convenient than dealing with firewood.

Economical. Pellets are less expensive than heating oil, propane, or electric-resistance heat, so you can save money if you would otherwise use those fuels. You may save more money with a pellet stove by heating only a few rooms instead of the whole house—though there are often ways to do that with other heating system as well.

Disadvantages of wood pellet heating

Noisy. There’s no getting around the fact that pellet stoves are noisy. There are typically two fans: one to supply combustion air to the burn pot and another to circulate heated air into the room. I find the noise annoying; my wife hates it. It’s certainly a far cry from a silent wood stove in our living room. There’s a Wiseway Pellet Stove that supposedly operates passively, but haven’t seen one in operation yet. Pellet boilers are noisy too, but they’re typically in the basement or a separate building, so it’s not a problem.

Electricity dependent. When you lose power a pellet stove or pellet boiler can’t operate (unless you have one of those new Wiseway stoves). This is an important consideration not only in rural areas prone to power failures, but also more generally in an age of global climate change with more intense storms forecast. With our own Quadrafire Mt. Vernon AE pellet stove, I bought a kit that allow me to operate the DC fans using a 12-volt automotive-type battery during a power outage. It won’t auto-start using the DC power, so you have to start it by hand with kindling or starter paste, but at least it can be used to keep a space warm when the grid is down.

Comfort. Pellet stoves don’t deliver radiant heat. I love pulling up a chair in front of our wood stove on a cold winter night and sitting down with a good book. That radiant heat seems to warm you inside and out. Pellet stoves—at least the one we have—don’t heat up in the same way and radiate heat. Nearly all the heat is delivered by fan-forced convection. It’s just not as pleasant.

Plastic bags. Unless you get pellets delivered in bulk you produce a lot of polyethylene plastic waste from the bags. The first two years we had our pellet stove I was able to buy bulk pellets that were delivered in reusable thousand-pound totes that sat on pallets. I had to carry the pellets upstairs in five-gallon pails, but at least I didn’t generate all that waste. Unfortunately, the company that had delivered those totes disappeared, and I had to switch to the more typical 40-pound plastic bags (which we reuse as trash bags). I believe that as pellet heating becomes more common, bulk delivery of pellets will become more available.

Complex. Unlike wood stoves, pellet stoves have moving parts that can wear out and that require maintenance. There are blowers, temperature sensors, an auger to deliver pellets, and other components. Most retailers recommend annual servicing, which can add significantly to the total operating cost of a pellet stove or pellet boiler.

Less control over the fuel. If you have a woodlot you can cut and split your own firewood. That’s not the case with pellets. Pellet factories use massive presses to extrude wood fibers through dies to create the pellets. Do-it-yourself pellets aren’t an option.

Not always cheaper. While pellets are less expensive than most other fuels, they may not be cheaper that natural gas or air-source mini-split heat pumps. Use our Heating Fuel Cost Calculator to compare costs per unit of delivered heat. In the Northeast, pellets typically track with heating oil—going up when heating oil prices spike, though generally remaining significantly lower. If you can order pellets in bulk rather than buying them in 40-pound bags, there may be some savings—but not all that much. And there have occasionally been shortages of pellets, driving prices up substantially.

Bottom line

Pellets are a mixed-bag, but they offer enough advantages in many situations to warrant consideration. They provide a user-friendly option for relying on a relatively local, renewable fuel source. If Europe is any indication, the use of pellet heat in the U.S. is likely to increase significantly in the years and decades ahead.

Check out the high-performing, low-emitting pellet stoves that we've found in our GreenSpec section.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-10-24 n/a 12099 Heating With Wood Safely and Efficiently

Understanding wood stoves and wood heat so that you can educate your clients.

Vermont Castings Encore-NC wood stove with an EPA emissions rating of 0.7 grams per hour. Click to enlarge.
Photo Credit: Vermont Castings

I’ve been heating primarily with wood since I bought our house 31 years ago, though there were a few years following our installation of an oil boiler when wood consumption dropped considerably.

Wood heat has a mixed record, though. It’s a renewable fuel and, assuming that new trees grow up to replace those cut for firewood, it is carbon-neutral, meaning that it doesn’t have a net contribution to global warming. But burning firewood produces a lot of air pollution; in fact, it’s usually our dirtiest fuel.

Fortunately, there’s a lot we can do to reduce the pollution generated by wood burning—and boost the efficiency.

Our discussion here focuses on wood stoves. Pellet stoves and larger central-heating wood boilers are quite different.

And I don’t even think of fireplaces as heating systems. They are aesthetic features that can add wonderful ambiance on special occasions—we use ours two or three times a year. Fireplaces burn very inefficiently, and they result in so much airflow up through the chimney that they can actually cause a net loss ofenergy.

Burning wood with minimum air pollution and maximum efficiency depends on three primary factors: the choice of wood stove; how the wood is stored and managed; and operation of the stove.

Choosing a Wood Stove

Since July 1, 1990, all new wood stoves sold in the U.S. have been required to carry U.S. Environmental Protection Agency (EPA) certification. (The 1988 law banned the manufacturing of non-EPA-compliant wood stoves after July 1, 1988 and the sale of such stoves two years later.) The EPA standard for non-catalytic wood stoves is 7.5 grams per hour of emissions and for catalytic wood stoves 4.1 grams per hour. By comparison, older, non-certified wood stoves typically produce 40 to 60 grams per hour.

Instituting stringent air pollution standards for wood stoves was a bold and controversial move by the federal government. It put over 80% of wood stove manufacturers out of business because it was too expensive for smaller companies to change their designs. (The federal government was able to push this through, I suspect, because wood stove manufactures were tiny with little political clout.) But it also dramatically reduced pollution from wood stoves and boosted combustion efficiency—reducing air pollution by as much as 85%.

Manufacturers achieved these improvements by significantly redesigning wood stoves—for example by insulating the firebox, adding baffles that lengthened the smoke path through the stove resulting in more complete combustion, and providing air-inlet holes above the combustion chamber to preheat combustion air. A few new-generation, non-catalytic wood stoves have EPA emissions ratings of less than 1 gram per hour, but all new wood stoves are far cleaner than their ancestors from two decades ago.

Properly Seasoning Firewood

The quality of the wood is tremendously important for clean, efficient wood burning. Wood should be seasoned at least six months off the ground and under cover after it is cut and split. If the moisture content of wood is high, that water evaporates as the wood is burned, keeping the combustion temperature low. Even the most advanced wood stove will generate a lot of pollution and burn inefficiently if green (unseasoned) wood is burned. Properly seasoned wood makes a hollow sound when two pieces are knocked together.

The six months’ drying of firewood should be considered a minimum. Ideally, several years’ worth of firewood should be kept on hand, with the oldest burned first. One way of organizing this is by stacking green wood outdoors, and then after a season or two moving a heating-season’s worth of wood into a fully covered shed, from which a supply is brought into the house as needed. Green wood should not be stored indoors, because of the significant amount of moisture that it will introduce to the house.

In splitting firewood, it’s a good idea to keep the diameter of the split logs relatively small, especially for smaller wood stoves, so that there will be a lot of surface area during combustion. Smaller logs will also dry out more quickly. 

Operating Wood Stoves Efficiently

To achieve optimal performance of a wood stove, it should be operated hot. Start the wood stove with crumpled newspaper and kindling. As the fire burns down, rake the coals toward the front or side of the stove, creating a mound (rather than spreading them out), and add several logs at the same time. In milder weather, build smaller fires, but still operate the stove hot, rather than keeping a large fire going and damping it down (restricting the air inlet). Regularly remove ashes so that air flow in the firebox is not impeded and there is plenty of room for wood.

The amount of smoke coming out of a chimney is a pretty good indicator of how cleanly (and efficiently) it is operating. If it generates lots of smoke, the combustion isn’t very complete and a lot of particulates (and other pollutants) are being generated.

This may occur if the wood isn’t property seasoned, as noted above, or it may indicate that the wood stove is being damped down too much (not providing adequate combustion air). Poor combustion may also occur if the chimney is clogged with creosote—a dangerous condition that can lead to chimney fires.

If a homeowner is unsure how to operate a wood stove for optimal performance, suggest that he or she ask at the store where it was bought. And tell homeowners to make sure that their chimney or flue pipe cleaned regularly—at least once a year.

To minimize pollution, household trash should not be burned in a wood stove. Nor should manufactured or painted wood (including plywood and particleboard), or pressure-treated wood—burning any of these materials is illegal in Vermont and some other states, and it should be illegal everywhere. Moldy or rotten wood should also be avoided, as should driftwood, since the salt may corrode the stove and stovepipe or result in toxic emissions.

For safety, installing smoke and carbon monoxide detectors is critically important; make sure that this is done. And suggest that batteries on battery-powered detectors be replaced at least annually, or whenever the low-battery alert sounds.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-10-17 n/a 12088 Good News and Bad News With the World Glut in Solar Panels

How China is affecting the world’s photovoltaic industry.

Workers at a Suntech factory in China. Due to the glut in PV, Suntech has closed a quarter of it's manufacturing capacity.
Photo Credit: Peter Parks, Getty Images for the New York Times

When China dives into a technology, it does so in a big way. Nowhere is this more the case than in photovoltaic (PV) panel manufacturing, where dramatic growth has not only taken a toll on other manufacturers around the world, but also now threatens its own PV industry through rampant oversupply.

This has significant implications for us here in the U.S.—both good and bad.

What happened?

China learned how to manufacture PV modules from leading-edge manufacturers in the U.S., Germany, and elsewhere, then figured out how to do it better and much cheaper than anyone else. In just a few years China came to dominate world PV manufacturing, leaving a trail of bankrupt Western manufacturers in its wake.

According to an in-depth article in last week’s New York Times, based on data from GTM Research, world PV manufacturing capacity in 2007 totaled about 5 gigawatts (GW), or 5,000 megawatts (MW). Of this, roughly 2 GW of capacity was in China. This year (2012), world PV capacity has grown to over 70 GW, and China’s share of that is about 50 GW. Just since 2009, Chinese manufacturing capacity has increased six-fold—from just 8 GW that year.

The problem is that demand for PV hasn’t been growing as quickly. World demand, which has been steadily rising, is now slightly over 30 GW (pretty impressive growth), but that’s less than half of current manufacturing capacity.

This glut of PV modules has resulted in plummeting prices. This has hurt not only manufacturers in the U.S. and the rest of the world that have been unable to match China’s manufacturing efficiencies, but also Chinese companies that are losing, according to the New York Times, as much as $1 for every $3 in sales.

Good for today’s buyers

Lower prices are great for those of us wanting to install PV systems at our homes or businesses. I’ve seen promotions recently for panels as cheap as $0.68 per watt. This is despite tariffs the U.S. put on Chinese modules earlier this year for dumping (selling at below cost) that amount to about 35%.

PV modules represent a significant chunk of the total system cost, but as costs of modules have dropped the share of total costs from other components has grown. In a typical residential system today, the PV modules represent only 20-30% of the total system cost. The “balance of systems” components include inverter, grid-intertie equipment, controls, and a mounting system, and of course there is labor. Balance-of-systems components are also dropping in price, but not as quickly as the PV modules.

Locally in southern Vermont, installers are putting in complete grid-connected PV systems with Chinese modules for as little as $3.40 per watt (for a 5 kW system), according to one installer I spoke with, while another, which uses American-made PV modules, listed system prices in the $3.80 to $4.00 range. Three years ago, $3.40 per watt wouldn’t cover the modules. In 2004, the average installed system cost in Vermont was about $11.00 per watt—more than three times today’s lowest cost. (The state-wide average is skewed by high-cost systems that include batteries for stand-alone applications.)

But the bottom line is that you have never been able to put in a PV system more affordably—even as state incentives have dropped. There remains a 30% federal tax credit, but the state incentive in Vermont has dropped, and the pot of money from which that incentive is paid gets depleted quickly each time its funding is renewed.

But not necessarily good for the health of the industry

While lower prices is attractive for those wanting PV systems, the shrinking diversity of PV manufacturers is a bad thing for the long-term health of the solar industry. Fewer companies and less geographic spread to those companies means that we’re at the whim of policies that we have no control over. Chinese companies have racked up huge debt. According to last week’s New York Times article, state-owned banks in China are carrying $18 billion in loans to PV manufacturers, while municipal and provincial governments have often provided loan guarantees.

Policymakers in China are apparently debating how to let PV manufacturers fail and how to choose which ones to keep afloat. In June of this year, GTM Research predicted that 21 GW of solar manufacturing capacity would come offline by 2015, due to this oversupply problem—as a result of company bankruptcies. If all of the companies were allowed to fail, we could quickly return to a seller’s market and prices could go back up.

The glut in Chinese PV manufacturing is also bad for Obama. The much-publicized bankruptcy of Solyndra Corporation, which had received significant federal support, was largely the result of lower-cost modules being available from China. (If anyone had asked me, by the way, I would have argued against supporting Solyndra, as I thought at the time the technology was gimmicky and unlikely to compete in the long term.) Solyndra wasn’t the only solar manufacturer to fail, and others will follow suit in the months and years ahead.

I’m hoping that enough of the world’s major solar manufacturers will remain in business with competitive enough prices to keep the cost of PV systems relatively affordable to those of us wanting to install them. We are making huge progress at adding significant solar capacity in the U.S., and I’m hoping to see that continue.

If you're looking to buy into today's market, check out our guidance in the photovoltaic section of GreenSpec.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.


2012-10-10 n/a 12014 A New Venture

Introducing the Resilient Design Institute: a new nonprofit organization that has been created in Brattleboro.

A massive ice storm, in which up to four inches of ice were deposited in early January, 1998, destroyed over 100 power distribution towers and tens of thousands of wooden utility poles, leaving millions without power for up to three weeks in Eastern Canada.
Photo Credit: Hydro Quebec

Some 27 years ago, following a five-year stint as director of the Northeast Sustainable Energy Association (which was then based in Brattleboro), I launched my own company focusing on information about environmentally responsible design and construction. That company, now called BuildingGreen and with a staff of 18, remains a leading player in the green building world—a trusted source of information on green building products, the place to find objective news on happenings in the green building world, an independent voice on the U.S. Green Building Council’s LEED Rating System.

It’s a great place to work and I’m thrilled to serve as executive editor at BuildingGreen and be able to research and write about all the cool stuff that our subscribers need to know. Nadav Malin has been doing a superb job at running the company since I handed the reins to him several years ago.

My shift away from company management at BuildingGreen has given me the space to focus on where we’re heading in the building industry and what sort of changes will be needed to solve the many challenges we face, led by climate change. My sabbatical last year, which I began with a contemplative 1,900-mile bicycle trip through the Southwest, provided an opportunity to delve deeply into this thinking.

What emerged was the need to find a new motivation for creating more sustainable, lower-impact buildings and communities. From what the climate scientists tell us, we’re simply not making rapid enough progress in slowing our consumption of carbon-dioxide-spewing fossil fuels, which are warming the planet. The motivation of “doing the right thing” isn’t driving change at a rapid enough pace.

Introducing the Resilient Design Institute

In light of this, BuildingGreen and I have launched the Resilient Design Institute (RDI). Resilience is the ability to bounce back from a disturbance or interruption, whether from an intense storm, flood, drought, wildfire, extended power outage, or shortage of heating or transportation fuel. Some of these interruptions have their origins in nature (“acts of God”), while others could be caused by human actions, such as terrorism.

Resilient design addresses the collection of strategies and practices that can help keep us safe and secure in our homes and communities during and following such events.

While sustainability and green building are motivated by altruism or “doing the right thing,” resilient design is a life-safety issue. Many of the end-points are the same, but the motivation is a little different.

I believe that resilience can ultimately be a stronger motivation for building highly insulated buildings, creating walkable communities, and carrying out other actions that will help us maintain safe, livable conditions should we find ourselves without power for three weeks or if political strife in the Middle East results in shortages of gasoline or heating oil. We get the comfort and security, and in so doing, we get a cleaner environment and help to mitigate climate change.

Achieving resilience

Resilience has a lot of components, including:

·      Superinsulated, passive solar houses that will never drop below 45–50°F even after weeks of power outage or loss of heating fuel;

·      Pedestrian-friendly and bicycle-friendly towns and cities that allow us to get around without cars;

·      Access to fresh water, and an ability to use it frugally, should drought cause shortages or power outages prevent us from pumping it;

·      Local food production that can help keep us fed should drought in the West cause crop failures or should diesel shortages limit trucking;

·      Strong communities in which neighbors get to know each other and are able to rely on one another during times of emergency; and

·      Healthy local economies that can weather recessions, perturbations in markets, and, ultimately, the inevitable transition from a growth economy to a steady-state economy.

Plans for the Resilient Design Institute

Our intent with RDI is to provide a go-to repository for information on all aspects of resilience, with a focus on practical solutions for achieving resilience in these various areas. Along with developing a comprehensive website with such information (, we will produce fact sheets, handbooks, white papers, course curricula, and other resources.

We will hold symposia and retreats to delve into various aspects of resilience. Topics of such meetings could include metrics for measuring vulnerability and resilience, incorporating resilience into building codes, resilient agriculture practices, and strategies for boosting the biodiversity and resilience of ecosystems. Foundation support will be sought for such gatherings.

We also hope to obtain foundation support for developing methodologies for assessing vulnerabilities and resilience of municipalities and institutions.

Visit us online

I encourage you to visit our website and give us some feedback. The website is new, but will expand over time. I’d love to hear your comments and recommendations. Send them to


Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.


2012-10-02 n/a 12000 Drainline Heat Exchangers

This simple system for recovering heat from wastewater makes a lot of sense—especially for families and commercial buildings that produce a lot of hot water.

Power-Pipe drainline heat exchanger. Heat from the hot water going down the drain pipe is transferred to water passing through the smaller-diameter pipes. Click to enlarge
Photo Credit: RenewABILITY Energy

Over the past few weeks I’ve written about various strategies to produce hot water efficiently. We’ve seen that tankless water heaters are more efficient than storage water heaters (though are not without their drawbacks), and we’ve learned that heat-pump water heaters produce two to three times as much heat per unit of electricity consumed as electric water heaters that rely on electric resistance heat.

But the unfortunate reality is that even with the most efficient methods of generating hot water, we still lose the vast majority of that heat down the drain. Domestic hot water is a once-through product. I’ve seen estimates that 90% of the heat in hot water is lost down the drain. Dan Cautley, an energy engineer with the Energy Center of Wisconsin, says that drain water “may be one of our largest untapped resources.”

It turns out that we can do something about that. Im the right application, drainline heat exchangers allow a significant portion of the heat from hot water going down the drain to be recovered.

How a drainline heat exchanger works

The process is pretty simple. A special section of copper drainpipe is installed beneath a shower (typically the largest hot water use in a home) or other hot wastewater source. This section of drainpipe has smaller-diameter copper piping wrapped tightly around it. The cold-water supply pipe leading into the water heater is diverted so that it flows through the small-diameter copper pipe.

When hot water is being pulled from the water heater to supply the shower, the water going into the water heater is preheated by the wastewater going down the shower drain. If it’s a tankless—rather than storage—water heater, the incoming water temperature will be higher, so less energy will be required to get it up to the needed delivery temperature—thus saving energy (though the tankless water heater has to be thermostatically controlled and, thus, able to deal with inlet water of varying temperature.

The man who invented the drainwater heater exchanger, Carmine Vasile, called the product a GFX, for “gravity-film exchange,” recognizing that water going down a vertical pipe forms a film that clings to the inner walls of the pipe where the heat can effectively be transferred through the copper to the supply water.

Several versions

There are four manufacturers of drainline heat exchangers that I’m aware of: Vasile’s original company, WaterFilm Energy of Medford, NY, and three Canadian companies: EcoInnovation Technologies of St-Louis-de-Gonzague, Quebec, which makes the ECO-GFX; ReTherm Energy Systems of Summerside, Prince Edward Island; and RenewABILITY Energy of Kitchener, Ontario, which makes the Power-Pipe.

Most of these have a single 1/2" copper pipe coiled around a length (typically three to five feet) of 2"- or 3"-diameter drain pipe.

The PowerPipe is a little different than the others. It has a header that splits the supply pipe into four smaller, square-cross-section pipes that provide more surface area for heat transfer.

Most of these manufacturers offer various lengths and diameters of drainline and can accommodate different supply pipe diameters.

No moving parts, nothing to wear out

The beauty of drainline heat exchangers is that there are no moving parts, nothing the wear out, and nothing to get clogged. Only fresh water goes through the small-diameter supply pipes; any hair or other materials pass through a standard, smooth drain pipe.

Maximizing recovery efficiency

According to an article in Environmental Building News, heat recovery efficiency can be as high as 60%—which can effectively double the water heating efficiency. Just how much benefit a drainline heat exchanger will provide will depend on usage patterns and how the plumbing in a house is configured.

Ideal for heat recovery is if all household members use the same shower (or have several showers drain through the same vertical length of drainline. It helps if the water heater is in a basement (or beneath the shower(s) and close-by, so that there is minimal length of supply piping from the heat exchanger to the water heater.

These systems are even more cost-effective in schools and commercial buildings that use a lot of hot water: school shower facilities, health clubs, laundromats, commercial kitchens, etc.


Installed in a new home, drainline heat exchangers typically cost $500 to $800 (including installation). Costs in multifamily buildings should be lower. In some states there are rebates available for such systems.

For more details on the individual products, check out our drainline heat exchangers in GreenSpec.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-09-26 n/a 11992 A Look at Heat Pump Water Heaters

New federal regulations beginning in mid-April 2015 will require that larger electric water heaters be heat-pump models. It’s time to pay attention to this option.

The GE GeoSpring heat-pump water heater is the quietest model I could find and the only one that's made in America.
Photo Credit: GE Appliances

Last week I wrote about “hybrid” water heaters, a relatively new type of water heater that includes features of both storage and tankless models. This week I’ll cover another type of water heater that is also (confusingly) referred to as “hybrid”: heat pump water heaters. These produce over twice as much hot water for each unit of electricity consumed as any other type of electric water heater (storage or tankless).

You’re going to be hearing a lot about heat-pump water heaters over the next few years, because new federal regulations that take effect in 2015 will require heat pump functionality for larger electric water heaters—more on that below.

Why it’s worth considering water heating carefully

Before diving into heat-pump water heaters and what makes them tick, it’s worth spending a minute to say why I’ve focused so much attention on water heating in this blog recently. As a fraction of residential energy consumption, water heating has become more and more significant over the past several decades.

In 1978, water heating accounted for approximately 14% of a home’s average energy consumption, according to the U.S. Department of Energy, compared to 66% for space heating. By 2005, those percentages had shifted to 20% and 41%, respectively. I assume that this isn’t because our water heaters are using a lot more energy, but rather that our houses are better insulated and our heating systems more efficient.

In an ultra-efficient Passive House (built to the German standard for low-energy homes that is gaining popularity in the U.S.), it’s not unusual for water heating to be the largest energy user in the house, and it can be as much as twice that of space heating.

Electric-resistance vs. heat-pump water heating

Up until recently, almost all electric water heaters relied on electric-resistance heat. Electric current flows through a special element with high electrical resistance, and the electricity is converted directly to heat. The conversion of electricity into heat is virtually 100% efficient—though heat loss from an electric storage-type water heater always results in an overall efficiency lower than 100%. (Note that if we’re looking at primary or source energy that the power plants use to produce the electricity, the efficiency is far lower.)

Heat pump water heaters are very different. Electricity isn’t converted directly into heat; rather it is used to move heat from one place to another. This is counter-intuitive because the heat is moved from a colder place (the room air where the water heater is located) to a warmer place (the water in the storage tank).

This seemingly magic process happens because a specialized refrigerant fluid is alternately condensed and evaporated in a closed loop. This process relies on phase changes of the refrigerant that capture and release significant amounts of heat.

A detailed explanation of the refrigerant cycle is beyond the scope of this blog. Trust me that it works. (It’s the same basic principle used in your refrigerator, which extracts heat from inside that insulated box and dumps it into your kitchen.)

The net result is that for every one kilowatt-hour (kWh) of electricity consumed, two or more kWh’s of hot water are produced. The energy factor, which is often thought of as a measure of efficiency, is 2.0 to 2.5 for most heat-pump water heaters on the market, while a 100% efficient electric-resistance water heater would have an energy factor of just 1.0.

Growing interest in these water heaters

There are a few heat-pump water heaters that have been on the market for decades, but these never really reached the mainstream. All that has changed in the past few years, however, as the largest water heater manufacturers, including A.O. Smith, Rheem, and GE have all introduced heat-pump water heaters.

While standard electric water heaters have no moving parts, heat-pump water heaters have compressors (to compress the refrigerant vapor causing it to condense into liquid) and fans (to circulate room air across the heat exchanger so that heat can be extracted from it).

Noisier than other water heaters

Be aware that these mechanical components produce noise—often significantly louder than a refrigerator. Heat-pump water heaters I’ve examined have noise ratings from 55 to 65 decibels (dB), which is a large range of variability (65 dB is ten times as loud as 55 dB). Most refrigerators are 40-50 dB.

If you are particularly sensitive to noise and don’t have an acoustically isolated place to install it, the energy savings from a heat-pump water heater might not be worth it.

New water heater regs to require heat-pump water heaters

New federal regulations that are due to kick in on April 16, 2015, will require that electric water heaters larger than 55 gallons have energy factors close to 2.0. The exact energy factor required is based on a formula that factors in the storage volume, but for all sizes in this category the required EF is close to 2—a performance level that can only be achieved with heat pump technology.

The energy factor requirements for smaller water heaters—up to 55 gallons in size—are also rising in April 2015, but will remain below 1.0 and will be achievable with a very-well-insulated electric-resistance water heater.

Heat pump water heaters rob heat from the house

Because heat pump water heaters extract heat from the air where they’re located, with most installations they increase heating loads somewhat. If you have an expensive fuel, such as baseboard-electric and are in a cold climate with a significant heating season, a heat pump water heater may not make sense.

These water heaters can make a lot of sense when there is a lot of waste heat, such as in a basement where an oil or gas furnace or boiler is located.

Size matters

Heat pump water heaters come in various sizes: from 40 to 80 gallons for products I know about. For most families, the larger sizes make sense, primarily because heat pump water heaters heat the water quite slowly—often just eight gallons per hour. Most heat-pump water heaters have different settings that regulate how readily the back-up electric-resistance elements will come on. With larger models, users can operate them on the heat-pump-only mode (the most economic) more of the time. The first-hour rating will give you a sense of recovery time, but which setting the water heater is on makes a big difference.

My next water heater will likely be a heat-pump model

I’m pretty sure we’ll install a heat-pump water heater in the house we’re currently renovating. Given what’s on the market today, I will probably select the GE GeoSpring water heater, a 50-gallon model that’s 10 dB quieter and half the cost of the German-made efficiency leader, Stiebel Eltron. I’ll also look at the Rheem Hybrid Electric and the A.O. Smith Voltex, which have the same energy factor (2.4) as the GeoSpring—though noise will be the biggest determinant. The GeoSpring is the only heat-pump water heater that’s made in America.

At an electricity cost of 15¢/kWh, a heat-pump water heater will be significantly cheaper to operate than the highest-efficiency, condensing propane water heater (we don’t have natural gas in southern Vermont)—even if propane were to drop to $2/gallon (far below it’s current price). Where natural gas is available—and assuming the price of natural gas remains so low—heat-pump water heaters will have trouble competing on economic grounds.

A big attraction to me of heat-pump water heaters is that they can be powered using a photovoltaic (solar electric) system. Our new place will be net-zero-energy and we hope to entirely avoid fossil fuels in the house.

Be aware that heat pump water heaters aren’t cheap. That GE GeoSpring I mentioned above lists for about $1,200, plus installation, and the Stiebel Eltron model costs about $2,500. Unlike electric-resistance water heaters, heat-pump models require condensate drains, which can add cost. By comparison, a standard electric or gas storage water heater can cost as little as a few hundred dollars.

Looking for a heat pump water heater of your own? Check out GreenSpec's guidance here.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.



2012-09-19 n/a 11404 Hybrid Water Heaters

A relatively new type of water heater combines features of both tankless and storage water heaters.

A.O. Smith's NEXT Hybrid water heater.Click to enlarge.
Photo Credit: A.O. Smith

In last week’s blog I compared tankless and storage water heaters and explained why tankless water heaters often don’t make that much sense.

This week I’ll describe a newer type of water heater that has some features of both storage and tankless designs and solves several problems that are common with tankless models. While these are referred to as hybrid water heaters, they are quite different from heat-pump water heaters, which are also often referred to as hybrid. I’ll cover heat-pump water heaters next week.

Some storage but also continuous hot water

As far as I can tell, the hybrid water heater was invented in 2006 by a relatively small company, Grand Hall USA of Garland, Texas, a company that also makes barbeque grills. Grand Hall’s Eternal Hybrid water heater defined this product type.

In 2010, the nation’s largest water heater manufacturer, A.O. Smith followed suit with their NEXT Hybrid, which the company has been promoting fairly actively.

Both are gas-fired tankless water heaters that have a small buffer tank, which is kept hot. The Eternal Hybrid has a two-gallon tank; the A.O. Smith NEXT Hybrid tank is probably about the same size, though the company doesn’t divulge the specifics.

There are two advantages of the buffer tank: first, it eliminates the so-called “cold water sandwich” problem in which someone taking a shower may suddenly get a shot of cold water from a standard tankless water heater; and second, it allows hot water to be delivered with even tiny loads, as might be delivered in a low-flow bathroom faucet. (With most tankless water heaters the burner isn’t activated unless the hot water flow exceeds 0.5 or 0.6 gallons per minute.) Like other tankless water heaters, its small size is another big benefit.

High efficiency, condensing technology

Both the A.O. Smith NEXT Hybrid and Eternal Hybrid use condensing combustion technology to exceed 90% efficiency. Grand Hall claims up to 98% efficiency with the Eternal Hybrid. The flue gases are cool enough that they are vented through a side wall using PVC or ABS plastic pipe. In fact, due to the acidic condensate, these water heaters should not be vented into a masonry chimney.

Like other advanced, state-of-the-art tankless water heaters, both products have electronic ignition rather than a standing pilot light.

Various sizes

The A.O. Smith NEXT Hybrid has a maximum gas input of 100,000 Btu/hour, which the company claims is enough to provide a “first-hour rating” of 189 gallons. (See last week’s blog for more on water heating ratings.)

A cut-away of Grand Hall's Eternal Hybrid water heater. Click to enlarge.
Photo Credit: Grand Hall

The Eternal Hybrid is available in three sizes with maximum gas inputs of 100,000, 145,000, or 195,000 Btu/hour. The minimum gas input is 16,000 Btu/hour for the smallest model and 26,000 Btu/hour for the other two. The largest of these models, the GU195, is available for modulating installations in which up to eight units are installed together for commercial applications.

The A.O. Smith NEXT Hybrid and the smallest Eternal Hybrid can be supplied with the 1/2-inch gas line; the larger Eternal Hybrid models require 3/4-inch gas lines.

Hot water output

The hot water delivery from these and all tankless water heaters depends on the temperature rise. The smaller, 100,000 Btu/hour models provide about 3.8 gpm at a 50°F temperature rise, but only 2.1 gpm at a 90°F rise. The largest Eternal Hybrid provides 7.6 gpm at a 50°F temperature rise and 4.2 gpm at a 90°F temperature rise—which should be plenty for two or three simultaneous showers.


As with most other tankless water heaters, cost is the Achilles heel. Prices of the A.O. Smith NEXT Hybrid are typically in the $1,800 to $2,000 range (not including installation), and I think the Eternal Hybrids are even more expensive. For the larger Eternal Hybrid models, there may also be the added cost of running 3/4” gas lines, instead of more typical 1/2”.

Yes, they appear to have some performance advantages over conventional tankless water heaters, but whether they will make economic sense over conventional gas storage water heaters will depend on the situation and usage habits.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-09-13 n/a 11395 The Difference Between Storage and Tankless Water Heaters

While they have higher efficiency, for most applications tankless water heaters don’t make sense.

Rheem's Prestige condensing tankless water heater has an efficiency of 94%, 11,000 to 199,000 Btu/hour gas input, a maximum hot water delivery (at a 45°F temperature rise) of 8.4 gpm, and a minimum flow rate of 0.26 gpm. Click to enlarge.
Photo Credit: Rheem Water Heating

There are two primary types of water heaters: storage and tankless. In this column I’ll try to explain the differences between these two approaches and offer some guidance on choosing between them. (There are also “hybrid” water heaters with features of both that I’ll cover in a future blog post.)

Storage water heaters

Most water heaters are storage models. These are insulated tanks holding 20 to 120 gallons with either electric heating elements or gas burners. The storage tank stratifies with hot water at the top and cold incoming water at the bottom, so that as you draw off hot water (from the top), you get consistently hot water until the hot water is nearly depleted. The “first-hour rating” tells you how many gallons of hot water can be delivered in an hour. 

Storage water heaters constantly lose heat through the tank walls. Even though the tank is insulated, the difference in temperature across that insulated wall is large, so even with a lot of insulation the stand-by heat loss is substantial. Gas-fired storage water heaters that have standing pilot lights replenish some of that lost heat with the pilot, but most of the pilot’s heat is lost up the flue.

Tankless water heaters provide constant hot water and energy savings

To address the issue of standby heat loss and running out of hot water, tankless water heaters (also referred to as demand water heaters) were developed decades ago. These are sometimes (especially in other countries) installed at the point of use, say in a bathroom, but in this country they are usually installed centrally in place of standard, storage water heaters.

A great feature of tankless water heaters is that they never run out of hot water—assuming the water heating capacity large enough to supply the needed hot water demands. They also don’t have stand-by losses. Because hot water isn’t stored in a tank, there is no heat loss when the water heater isn’t operating (though there will be some losses through the pipes during use).

A 2008 Consumer Reports article reported that gas-fired tankless water heaters used about 22% less energy than their storage-type counterparts. A 2010 study by the Center for Energy and Environment in Minnesota found that gas-fired tankless water heaters save an average of 36% over storage water heaters. So far, so good.

The size of heating elements

A key advantage of storage water heaters is that the heating element(s) can be fairly small. Because a significant volume of water is stored and because the tank remains stratified as hot water is drawn off, a properly sized storage-type water heater can provide a family’s hot water needs without requiring a very large flow of gas or electricity to heat the water.

Most gas-fired storage-type water heaters have relatively small burners, typically 30,000 to 50,000 Btu/hour (not much larger than the larger burner on a gas range). This means that a half-inch-diameter gas line is usually adequate to supply the water heater. It also means that the air intake (supply of combustion air) can be fairly modest in size.

Gas-fired tankless water heaters, on the other hand, often have much larger burners. A typical whole-house model, sized to allow two showers to be used at the same time or for someone to shower while the clothes washer or dishwasher is operating, will have a burner producing as much as 180,000 Btu/hour; the largest tankless water heaters have burners over 300,000 Btu/hour. Supplying the natural gas or propane to such a large burner requires a larger gas-supply line (typically 3/4-inch) than needed for storage water heaters—not an insignificant consideration.

Along with the large gas line, these tankless water heaters require a lot of combustion air. A small, 125,000 Btu/hour model operated at full capacity requires about 30 cubic feet per minute (cfm) of air for complete combustion, and a large, 180,000 Btu/hour model requires up to 45 cfm of air at full capacity. Such large airflow requirements can limit the options for placement.

Bigger challenges with electric tankless water heaters

An electric tankless water heater large enough to serve a whole house requires a huge current draw. A Seisco Model RA-28 that supplies 2.5 gallons per minute at a 76°F temperature rise draws as much as 116 amps at 240 volts! Most homes have only 200-amp service, and the multiple breakers and wiring required for such large current flows are expensive.

For utility companies, the idea of a lot of customers switching to electric tankless water heaters is downright scary, since hot water loads typically fall during periods of peak morning and early-evening power consumption. Utility companies are required to have capacity available for whatever the demand is, and if a lot of electric tankless water heaters were installed in a service district that would result in a significant increase in those peaks.

Flow rates

Some tankless water heaters have a minimium flow rate as high as 0.5 or 0.6 gallons per minute, meaning that at lower flow rates they won't come on. This can be a problem with low-flow plumbing fixtures, such as bathroom faucets. Fortunately, manufacturers are responding to this concern. The Rheem H95 condensing tankless water heater pictured with this blog, for example, has a minimum flow rate of 0.26 gpm, the lowest I've seen—though the minimum "activation rate" is somewhat higher at 0.4 gpm.

Higher cost for tankless water heaters

While tankless water heaters save energy compared with storage water heaters, that doesn’t mean they are cost effective. Both the Consumer Reports and Minnesota study mentioned above reported that the significantly higher cost of tankless water heaters resulted in payback periods longer than the expected lifetimes of the water heaters. Consumer Reports found the cost of tankless models to range from $800 to $1,150 plus about $1,200 for installation, compared with $300 to $480 for storage water heaters and $300 for installation.

The Minnesota study reported a 20- to 40-year payback for the tankless water heaters.

With certain usage patterns, though, the numbers could change. In a vacation home that is only used for an occasional weekend, the standby losses can be a huge percent of the total energy use for water heating, and a tankless model might make more sense. Or, in a commercial building in which a lavatory faucet is far away from the water heater and the hot water demand is very low, a small point-of-use tankless water heater may make sense—even an electric model.

Increased maintenance

On top of the questionable economics, tankless water heaters have significantly greater maintenance requirements than storage models. Models designed for outdoor installation (where supplying combustion air is not a problem) include sophisticated freeze-protection systems. In places with hard water, scale build-up is a significant problem. If the hardness is above 11 grains per hour, experts recommend installing a water softener, according to Consumer Reports, and special provisions may be needed during installation to allow periodic flushing the heat exchanger coils with a vinegar solution.

Bottom line

The bottom line is that tankless water heaters simply don’t make sense for most whole-house applications. There are exceptions, as noted above, but for the vast majority of residential applications, storage water heaters make more sense. Members of can learn more about water heaters in GreenSpec.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-09-06 n/a 11362 Saving a Little More Energy With Exit Signs

Those ubiquitous exit signs use a huge amount of electricity; a little-known alternative to conventional LED products offers surprising savings.

An exit sign at Yale's LEED-Platinum Kroon Hall. Click to enlarge.
Photo Credit: Alex Wilson

In the years that I’ve been writing about energy and energy conservation (longer than I really want to admit), I’ve reported on several dramatic transitions in how we illuminate the exit signs in commercial buildings. For an energy geek, it’s been an exciting technology to watch.

Why care about exit signs?

Why do we even pay attention to exit signs—those ubiquitous red or green illuminated signs that direct our escape from a building should the need arise? They can’t use very much energy, can they?

Each one uses relatively little electricity, but they are on all the time. And we have a lot of them in our schools, factories, and office buildings. The U.S. Environmental Protection Agency estimates that there are more than 100 million exit signs in use today in the U.S., consuming 30–35 billion kilowatt-hours (kWh) of electricity annually.

That’s the output of five or six 1,000 MW power plants, and it costs us $2-3 billion per year. Individual buildings may have thousands of exit signs in operation.

From incandescent to fluorescent to LED

When I first wrote about exit signs, the vast majority of them were illuminated with two 15- or 20-watt incandescent lamps. These lamps often lasted less than a year, and an exit sign with two of these lamps used nearly as much electricity per year as an Energy Star refrigerator uses today. For businesses, the labor cost of replacing those incandescent bulbs could be nearly as expensive as the electricity they consumed.

Thus, there was a lot of excitement in the early 1980s when compact fluorescent lamps (CFLs) made their way into exit signs. One or two CFLs using a total of 10–15 watts replaced up to 40 watts of incandescent lighting, and they lasted several times as long. The low power factor of these CFLs actually reduced the energy benefit for utility companies (a complex issue that I won’t bore you with), but end-users saved a lot of money. The biggest downside was the small amount of mercury in each CFL.

CFL lighting for exit signs didn’t last long, however. By the early 1990s, LED technology emerged for exit signs. LEDs are solid-state lighting devices that use relatively little electricity, do not require mercury (as is required in fluorescent lamps), and last a very long time. Early LEDs were usually red or green (think of those indicator lights on your stereo equipment), which worked fine in exit signs. (White LED lighting for general illumination is a lot more challenging.)

The first LED exit signs dropped the electricity use down to 5–7 watts, and there are LED exit signs on the market today that use as little as 1.8 watts and still meet the emergency egress standards of building codes.

Energy efficiency regulations gave a huge boost to LED exit signs. A revision of the Energy Policy Act of 2005 set a maximum electricity consumption of exit signs at 5 watts (effective in January 2006), which effectively eliminated both incandescent and CFL exit signs.

With such low electricity consumption, LED exit signs can be coupled with relatively small battery back-up systems—a requirement (and significant environmental impact) for most exit signs.

Just as significant for bottom-line-conscious businesses is the very long life of LEDs. Most are rated at 50,000 hours—many times as long as incandescent lamps. The power factor is also better than that of CFL exit signs, which makes utility companies happy.

Enter electroluminescent exit signs

There isn’t a lot of additional gain to be squeezed out of a 2-watt LED exit sign, but there is some. A quite different technology allows fully compliant exit signs to be powered with less than a fifth of a watt—at least a ten-fold drop compared with most LED products.

Electroluminescent or light-emitting capacitor (LEC) technology produces a uniform layer of light rather than discrete point sources (as with LEDs). Limelite Technologies, the leading manufacturer of electroluminescent exit signs, describes how the technology works on its website.

Again, the savings from each one isn’t that great, but spread over tens of millions of products, the savings could be very significant.

Exit signs in our GreenSpec Directory

In our GreenSpec product database, we briefly listed CFL exit signs, then included dozens of manufacturers of LED exit signs. Today we list just two products: LimeLite of Maxwell, Texas (also at, which produces the Series 16 and Design Select exit signs, consuming just 0.18 watts each; and Greentorch (also at, which makes a wide range of LED exit signs including an LEC model using 0.25 watts and having an expected life of 30 years.

Our detailed criteria for exit signs are described here.

Exit signs to avoid

While there is a lot of good stuff in the exit sign world, there are some products to watch out for. One of them is “zero-energy” photoluminescent exit signs, which harvest ambient light from the space and will deliver needed emergency exit sign illumination for up to a couple hours during a power outage. These use glow-in-the-dark materials that are familiar in toys.

The problem is that code requires fluorescent lights to shine on these photoluminescent exit signs so that they will be fully charged and ready to provide that emergency illumination during a power outage. You will use more energy for the fluorescent light source to charge the exit sign than a standard LED exit sign will use to operate. Yes, the battery can be eliminated, but that still doesn’t justify the additional electricity use (in most cases).

The other product I like to stay away from is radioluminescent, or tritium-powered, exit signs. Tritium, a radioactive isotope of hydrogen, provides the illumination. While tritium emits fairly low-energy beta particles that aren’t strong enough to penetrate our skin, if we breathe in tritium gas or swallow tritiated water, the radiation can damage cells in our body. It’s a product I’d rather keep away from.

A detailed summary of exit sign technologies, including discussion of why photoluminescent products don’t make sense, is available in our EBN feature article on the evolution of exit signs.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.



2012-08-29 n/a 11315 Insulation to Keep Us Warm—Not Warm the Planet

An update on getting the global warming potential (GWP) out of insulation materials.

Today's closed-cell SPF has a global warming potential of 1,430, but if producers adopt new HFO blowing agents, it will drop to close to zero. Click to enlarge.
Photo Credit: John Straube

I’ve been pretty vocal about a big problem with some of our most common insulation materials: that they are made using blowing agents that are highly potent greenhouse gases.

All extruded polystyrene (XPS) and most closed-cell spray polyurethane foams (SPF) are made with HFC (hydrofluorocarbon) blowing agents that have global warming potentials (GWPs) many hundreds of times greater than that of carbon dioxide. (My apologies for contaminating this column with so many acronyms!)

Insulation: good news, bad news

Insulation materials help our homes save energy and, in so doing, they reduce the combustion of fossil fuels and the release of greenhouse gases.

But if the insulation material itself is made with a very-high-GWP blowing agent that may ultimately escape from the insulation, adding a lot of insulation may actually be a bad thing from the standpoint of mitigating climate change. All that was spelled out in my blog post two years ago, “Avoiding the Global Warming Impact of Insulation” and, in greater detail, in the EBN feature article on the same topic.

OK for ozone, bad for climate

With XPS, the blowing agent HFC-134a has a GWP of 1,430, meaning that it’s 1,430 times as potent as carbon dioxide (which is defined as having a GWP of 1). Nearly all closed-cell SPF is made with the blowing agent HFC-245fa, which has a GWP of 1,030.

Relative to global warming, these blowing agents aren’t as bad as the CFCs that were used originally, but they are as bad as the HCFCs (hydrochlorocfluorcarbons) that were adopted as second-generation blowing agents. (Both HFCs and HFOs are considered totally safe for the ozone, which is why CFCs and HCFCs have been phased out.)

Blowing agents: the next generation

Anyway, given all this, I’ve been closely following the developments by industry in coming up with alternatives that are neither ozone depleters nor significant greenhouse gases.

Two years ago, it appeared that the leading candidates were HFOs (hydrofluoroolefins), and Honeywell announced the development of such a product in 2011. And indeed, it was just announced last week that Whirlpool, the nation’s largest appliance manufacturer (with such brands as Maytag, Amana, Jenn-Air, and KitchenAid, along with Whirlpool), was switching to a new HFO blowing agent for the polyurethane insulation in all of it’s refrigerators.

Whirlpool will be using the new Solstice Liquid Blowing Agent made by Honeywell, one of the nation’s three producers of blowing agents (along with DuPont and Arkema). Solstice HFO has zero ozone depletion potential and a GWP of just 4.7 to 7.0—similar to that of the various hydrocarbon blowing agents used in expanded polystyrene and polyisocyanurate—and insignificant relative to global warming.

Efficiency boost an added bonus

Further, Solstice HFO will boost the R-value of the insulation material slightly. Compared with HFC-245fa, this HFO produces insulation with 2% higher R-value, and compared with hydrocarbon blowing agents it offers an 8%–10% improvement, according to Honeywell.

While the change is exciting, it is not immediate. The HFO has just received its approvals from the government, and it will take a while to ramp up production and convert refrigerator factories to the new foam. Whirlpool expects to begin incorporating the new blowing agents into its refrigerators in late 2013.

Spray-foam manufacturers slower to adopt HFOs

But what about the closed-cell SPF insulation that is commonly used to insulate buildings?

SPF manufacturers will probably be replacing the HFC-245fa with HFO…but it’s unclear exactly when that will happen. Rick Duncan, the technical director at the Spray Polyurethane Foam Alliance (SPFA), the trade association serving the SPF industry, told me that some SPF manufacturers (“system houses”) are conducting field trials with the new HFO blowing agents, but not all of them.

Unlike in 2003 when federal regulations mandated a switch from HCFC to HFC blowing agents due to ozone depletion concerns, there are no similar regulations requiring a switch from HFCs to HFOs.

It’s up to us

And the conversion takes time and is expensive—about one year and at least $100,000, says Duncan. With the building industry still in an economic slump, producers aren’t looking to spend a lot of additional money on product development.

Duncan believes, however, that when a new life-cycle assessment (LCA) report on SPF comes out that SPFA is now finalizing, customers will begin asking for lower-GWP foam and manufacturers will respond by producing it. From an environmental standpoint, open-cell SPF (which doesn’t include HFC blowing agents) has just 1/20th the global warming impact of closed-cell SPF.

12 inches of sub-slab XPS was used in this Passive House in New York State. It will take several hundred years of energy savings to pay back the global warming potential of that insulation. Click to enlarge.
Photo Credit: Jordan Dentz, The Levy Partnership, Inc.

Less action in the XPS camp

I was not able to get as much information from the extruded polystyrene industry about when the HFC-134a might be replaced with a lower-GWP blowing agent and whether there is a gaseous form of HFO that could work for that industry. (While a liquid blowing agent is used in producing SPF, a gaseous blowing agent is required for XPS.)

Jan McKinnon, the senior communications manager at Dow Building Solutions (manufacturer of Dow Styrofoam XPS), says that the company is looking for ways to reduce its greenhouse gas emissions. “Since the launch of our new formulation in 2010 [converting from HCFC-142b to HFC-134a], we continue to look at lowering our blowing agent global warming potential, and we have an active process in place to reduce it by 15%,” she told me. She said that they are actively evaluating alternative blowing agents for XPS, “but most of these technologies are still in their infancy.”

Not a great time to invest in products

Both the SPF and XPS industries have already gone through two major transitions: from CFC to HCFC blowing agents and then from HCFC to HFC blowing agents.

With a weak building economy and depressed sales of building materials, enthusiasm for a third major conversion has been limited. But I believe that there will be growing demand to produce products with as little impact on global climate change as possible—and if this year’s heat and drought continue, that demand may well grow.

Let’s hope so.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-08-22 n/a 11298 The End of Peak Oil?

With new oil discoveries and more effective extraction methods, the world is probably many decades away from peak oil.

A "Hubbert Curve" of world oil production, showing the peak in this decade, which was widely predicted just a few years ago. Click to enlarge.
Photo Credit: Energy Watch Group, UK.

I first wrote about “peak oil” in 1998, reporting on an in-depth article in Scientific American by petroleum geologists Colin Campbell, Ph.D. and Jean Laherrère. Campbell and Laherrère believed that up to that time the world had consumed about 800 billion barrels of oil (BBO), and the known reserves of conventional crude oil totaled about 850 bbl in 1996 and another 200 BBO of conventional oil was yet to be discovered.

The result, they argued, was that the world would reach the half-way point—or the peak—in (conventional) world oil production within the first decade of the 21st century. That peak would occur, they argued, when cumulative world oil consumption reached about 925 BBO. (At that time the world was consuming 23.6 BBO per year.)

The significance of peak oil is that once that point is reached, so the proponents argue, annual oil production will begin an inexorable decline with a concomitant rise in cost. It would become too expensive to use oil for many uses and the “end of the oil age” would be in sight.

This was a resonant chord for a lot of people—myself included. The end of cheap oil would mean the shift to cleaner fuels and a slowing of the release of greenhouse gasses. It would result in improvements in fuel economy of vehicles; it would encourage homeowners to shift to cleaner heating fuels; and it would spur the development of plug-in hybrid vehicles that could be powered by solar electricity. “Peak Oil” became a rallying cry and the subject of dozens of books.

So where are we today, relative to peak oil?

Statistics on world oil production, consumption, and reserves are tracked by various entities; one widely quoted source is the BP Statistical Review of World Energy; I am pulling numbers from the 2012 edition, which includes data through 2011. Unlike The Campbell and Laherrère statistics quoted above, the BP statistics include unconventional oil, such as tar sands and very deep deposits.

Proven reserves of oil, according to the BP report, totaled 1,653 BBO at the end of 2011. This compares with proven reserves in 2001 (ten years earlier) of 1,267 BBO and proven reserves in 1991 (twenty years earlier) of 1,033 BBO. In other words, since 1991, the proven reserves have increased 60%. (Some challenge the BP statistics; you can read a contrasting view in this post on The Oil Drum.)

Global consumption of oil in 2011 totaled 32.1 BBO, up from 26.1 BBO in 1996 (according to the BP statistics). As a point of reference, 32.1 billions of barrel per year converts to about 1,000 barrels per second. (One barrel is defined as 42 gallons, so that’s about 42,000 gallons per second.) Big numbers.

Since the end of 2011, as more deep-sea Brazilian oil and oil recovered through hydraulic fracturing (fracking) comes online, I’m guessing that the rate of increase in proven reserves will only increase for the next few decades.

Furthermore, I predict that the once all-important distinction between “conventional” and “unconventional” oil will break down over time. As technologies improve for very deep drilling (measured in miles rather than feet), such wells will become more common. Fracking will become more common as a strategy for rejuvenating oil fields that had been considered depleted. I don't like this, particularly given the huge risks and environmental impacts of such extraction methods, but I fear that it's the reality.

Reduce Oil Production for Other Reasons

What all this means, I believe, is that we should shift away from the motivation of peak oil as our reason for promoting alternatives. A peak in world oil production—due to supply limits—just isn’t going to happen anytime soon, perhaps not even in our lifetimes. We need to use other arguments for curtailing our consumption of oil and other fossil fuels, including coal and natural gas.

Fossil fuels are highly polluting in their extraction, combustion, and (especially with coal) waste disposal. More importantly, these energy sources release into the atmosphere vast quantities of carbon dioxide, the most significant of the greenhouse gasses that are contributing to global climate change.

While the political world has shifted away from climate change as an issue, I believe that is a very short-lived phenomena that will evaporate as quickly as those rare showers on Nebraska corn fields this summer. It wouldn’t surprise me if climate change returns as an issue of debate as soon as the November elections this year.

Temperature records are being broken by the thousands this year, with July the hottest month ever recorded in the U.S.—going back to 1895, when widespread recordkeeping began. Drought covers 63% of the nation, and is driving up the cost of food worldwide (see the Drought Monitor, which is updated weekly). Dry conditions are fueling record fires in Colorado and elsewhere. Scientists are almost universally accepting of the role humans have played in creating this climate change; as more of the public feels the effects I believe they will force politicians to finally stand up and do something about it.

Forget about peak oil. Let’s get on with dealing with climate change.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-08-15 n/a 11287 30 Years Later – Fixing Those Drainage Problems

Finally fixing the basement drainage problems that have plagued my house for 30 years

I tried fixing the drainage years ago, but my fix failed at the basement window wells, including the one shown here on the back of the house after digging it out, exposing the EPDM drainage layer. Click to enlarge.
Photo Credit: Alex Wilson

When I bought the house in West Dummerston, Vermont, where my wife and I have lived for the past thirty years, one of the first things I did was fix the drainage problems that were dumping water into our basement….

Or so I thought. Let me explain.

When I moved into the 1780s house there was a hill on the west side that channeled runoff right into the dry-stone foundation. During rainstorms rivulets of water would flow into the basement with abandon. The house had only survived so long because the soil is very sandy. Moisture that got into the basement would quickly soak into the ground and disappear.

Step one was to change the topography. I hired an excavation contractor to move several hundred yards of earth from the west side of the house, creating a bit of a swale to direct runoff away from the house.

Step two was to dig a deep trench about three feet from the house to try to intercept the water flowing toward the foundation. I couldn’t dig that trench right against the foundation, because we have a rubble foundation that is vertical on the interior but sloping away from the house on the exterior.

I dug the trench by hand to the depth of the basement floor (I was thirty years younger back then and full of energy), then created a sloped plane where I could install two inches of extruded polystyrene insulation and a plastic moisture barrier. I wanted not only to deal with drainage, but also to insulate the basement while I was at it.

I installed perforated drainage tile at the bottom of the trench, backfilled with crushed stone, dealt with the tricky detailing at the window wells, and finished it off. Water flows off the roof eaves and is directed away from the house….

The basement window and window well is gone. The original Tyvek is folded up as new drainage layers are added. Click to enlarge.
Photo Credit: Alex Wilson

At least that was the plan.

But with heavy rains, I discovered that my drainage layer didn’t work at the window wells. Water somehow made its way around the plastic and into the basement—carrying the sandy soil with it.

Fifteen years later, I tried a fix—hiring a builder this time (I had less of that youthful energy by then) to expose the top of the trench and install a layer of EPDM rubber mat. Again, we dealt with the tricky detail at the window well….

And again, we failed. Moisture still came into the basement and still carried the sandy soil with it. We ended up with a sinkhole in our lawn. The folds around the window wells just didn’t work.

That brought us to this summer. We’re wanting to fix up the house so that we can put it on the market in the next year or so as we move to the farm we bought down the road, and I knew that I would finally have to fix these drainage problems before selling the house.

Working with a different builder, my friend Eli Gould, we decided to eliminate the windows altogether so that the drainage could be continuous from the wall system down to the sloped insulation. Building scientist friends of mine, Terry Brennan and Andy Shapiro, were staying at our house one night when we were thinking about this solution, and they concurred that eliminating those windows was a no-brainer.

We now know that basement windows shouldn’t be used for ventilation in our climate—because they introduce more moisture than they remove. Yes, we will lose some natural light, but that’s not a big deal since we don’t use the basement for anything besides our heating system, indirect hot water tank, pressure tank for water, freezer, and some limited storage.

Re-clapboarding the front of the house. Click to enlarge.
Photo Credit: Alex Wilson

So here we are. Done. The walls have four layers of drainage, lapped so that water can’t sneak in. We use a house wrap, Grace Ice & Water Shield, EPDM, and metal flashing (for protection on the outside). We installed an additional length of drainage tile, and more crushed stone. We replaced some rotted clapboards at the bottom of the wall. I think it’s going to work like a charm!

What we have created is essentially an underground roof (a name given to this approach by building scientist Bill Rose). Water comes off the eaves of the roof and hits the crushed stone, dropping down and being carried away by the drainage layers and drainage tile. The sloped insulation saves some energy and keeps the basement from freezing.

Looking good so far!

Do you have similar drainage problems? Check out our GreenSpec guide to help you find foundation and slab drainage products.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-08-08 n/a 11209 Building Performance Laid Bare: Energy Reporting Laws Taking Effect
Laws taking effect now are advertising the real energy performance of large buildings in cities like New York for all to see.

Monitoring your energy use isn’t just a good idea—it’s now the law in some cities and states. As we report on in our new EBN feature article, Energy Reporting—It’s the Law, the public is about to find out just how much energy is being consumed in thousands of large buildings in New York City, and similar laws are being enacted and taking effect in several other U.S. cities.

Benchmarking vs. Reporting: What’s the Difference?

Many of the laws that require energy reporting are called “benchmarking” laws. But actual benchmarking may or may not be part of the process. These key definitions should help cut through the confusion.

  • Reporting: The recent spate of energy benchmarking laws that apply to commercial buildings all require that the building owner report the building’s energy use using the online Energy Star Portfolio Manager. In some cases owners (or their consultants) have to collect and enter the data themselves; in others they can just enter basic building information and authorize the utility company to provide the data.
  • Benchmarking: Once the data is in Energy Star Portfolio Manager it might or might not be compared against other, similar buildings. If the building is of a type (such as office, school, etc.) for which Energy Star has reliable data, then it can be compared against that data set and assigned a comparative benchmark score. These scores are adjusted to account for variables such as square footage, number of occupants, and how the space is used.
  • Disclosure: Voluntary use of benchmarking programs like Portfolio Manager has been an option for building owners for over a decade. Requiring owners to disclose either their data or a benchmark score is a more recent development (although one New York State “Truth in Heating” law for homes goes back to 1980). The laws all require that owners disclose their Energy Star Portfolio Manager data to the city or state. Some cities will post that information publicly, while other cities and states only require that it be disclosed to parties involved in a real estate transaction.

Owners get nervous about being embarrassed by having to report poor energy efficiency—or arguably, by reporting a simple number when a more complex story must often be told (such as one involving high occupancy rates contributing to high energy use) to understand a building’s performance. A reporting requirement in Philadelphia was passed over the objections of one owners’ group.

How much effect will the laws have?

We’re on the cusp of a new era of building energy labels. Here are some of the things we're wondering about.

  • How strong a role will reporting, benchmarking, and disclosure play in “raising the floor” of building performance, and how will it interact with efforts like the LEED rating system to “raise the ceiling”?
  • To what extent will the culture of building owners move toward embracing transparency and improved performance, versus reporting being be seen as just another law to minimally comply with?
  • Will energy reporting programs be seen as a low-cost way for governments to encourage efficiency in their real estate sectors, or will they fall victim to budget-cutting axes in the tough economy?
  • How far will energy reporting mandates spread across the U.S., and how quickly?
  • What new tools and utility programs will develop to make reporting easier, and the results more comprehensible?
  • Will more widespread reporting lead to greater integration between design and construction on the one hand and operations and maintenance on the other?

Please post your thoughts below! And of course, for more investigation, see Energy Reporting—It’s the Law in EBN.

Image note: We love the EnergyGuide image shown here, and since it's now all over the Internet we don't know who originated it. If you know, let us know!

2012-07-31 n/a 11208 Expanded Cork - The Greenest Insulation Material?

Introducing all-natural expanded cork boardstock insulation to the North American market.

Expanded cork insulation is available up to 12 inches thick and can be used much like polyiso. Click to enlarge.
Photo Credit: Amorim Isolamentos

I’m always on the hunt for the latest, most interesting, and most environmentally friendly building materials, and I have particular interest in insulation products—partly because many conventional insulation products have significant environmental downsides. (See “Avoiding the Global Warming Impact of Insulation” and “Polystyrene: Does it Belong in a Green Building?”)

So I was thrilled to learn about expanded cork boardstock insulation made by the Portuguese company Amorim Isolamentos and just now being introduced into the North American market. Francisco Simoes, of Amorim, visited our office in Brattleboro in June and told us all about it.

Familiar to wine drinkers as the traditional bottle-stopper, cork is a natural product made from the outer bark of a species of oak tree that grows in the western Mediterranean region of Europe and North Africa. The bark is harvested after trees reach an age of 18–25 years and it regenerates, allowing harvesting every nine years over the tree’s 200-year life.

The outer bark of cork oak tree can be harvested every nine years. Click to enlarge.
Photo Credit: Amorim Isolamentos

In Portugal, the world’s leading producer of cork, these oak trees are federally protected, and many cork forests are certified to Forest Stewardship Council (FSC) standards. Harvesting is done by hand, much as it has for over 2,000 years. While cork oak forests in Portugal are expanding, cork’s market share for bottle stoppers is dropping as plastic stoppers and screw-off caps become more common—motivating the company to look for new markets.

Cork as a building material

I have long been a fan of cork flooring, floor underlayment, and acoustical wall coverings. These materials are made from residual cork that remains after punching cork bottle stoppers from the bark—which consumes only 25%–30% of the bark.

For cork flooring and these other products, the cork granules are glued together with a binder and then sliced into the finished products.

Expanded cork insulation is quite different. The same cork granules are used, but they are exposed to superheated steam in large metal forms. This heating expands the cork granules and activates a natural binder in the cork—suberin—that binds the particles together. In an in-depth product review about expanded cork insulation in the August issue of Environmental Building News I describe the fascinating history of this process (it was invented by accident in New York City in the late-1800s).

A billet of expanded cork coming out of an autoclave. Click to enlarge.
Photo Credit: Amorim Isolamentos

After producing these large billets of expanded cork, they are sliced into insulation boards in a wide range of thicknesses—in both metric and inch-pound (I-P) sizes. In I-P units, thicknesses from a half-inch to 12 inches are available—with dimensions of 1' x 3' or 2' x 3'.

The material is 100% natural, rapidly renewable as defined by the LEED Rating System, durable yet ultimately biodegradable, produced from sustainable forestry operations, and a by-product from the cork bottle-stopper industry. Though there is significant shipping energy required to bring it here, shipping by ocean-going vessel is relatively energy-efficient. It’s hard to imagine a greener building material.

Cork insulation performance

Expanded cork insulates to R-3.6 per inch. It has a density of 7.0–7.5 pounds per cubic foot and compressive strength of 15 psi (with 10% compression). It is intermediate in its permeability to moisture—with a 40 mm layer having a permeance of 2.2 perms. Although the expanded cork insulation gives off a smoky smell, a test report I examined showed the material to pass France’s stringent requirements for a dozen volatile organic compounds (VOCs) with flying colors. Cork also has superb sound-control properties.

A 40 mm layer of expanded cork insulation resists burn-through for over an hour. Click to enlarge.
Photo Credit: Amorim Isolamentos

From a fire-resistance standpoint, it meets the European Class E designation (the standard met by other rigid insulation materials) without the need for flame retardants that are used in the most common boardstock insulation products. A 40 mm-thick piece of the boardstock insulation held over a torch will resist burn-through for an 60–90 minutes, compared to less than 10 seconds for expanded or extruded polystyrene, which meets the same Class E designation. (The flawed manner in which we determine fire-resistance properties of materials is the topic for another article.)

Cork insulation has been used as a rigid insulation material for decades in Europe. It is not uncommon to install an 8- to 10-inch layer on exterior walls and a 10- to 12-inch layer on roofs. The first Passive House built in Austria (in 1995) used a 350 mm layer (nearly 14 inches) of the material. It is typically used as an exterior insulation layer, much like polyisocyanurate.

Cost and availability

North American distribution channels are just being set up, so pricing is far from certain. But Simoes told me the price to a distributor will be about $0.70 per board-foot, not including shipping, mark-ups, or the exchange rate. If those mark-ups come to 50%, the cost per board foot would be $1.05 and the cost to achieve R-19 would come to about $5.50 per square foot for cork, vs. $1.10 – $1.60 for polyisocyanurate insulation and $2.00 – $2.25 for extruded polystyrene.

That’s a significant upcharge for cork, but you end up with one of the greenest building materials anywhere. I’m so excited about expanded cork insulation, in fact, that I’m hoping to use it on an upcoming building project later this year.

You can read my full review of Amorim Isolamentos’ expanded cork insulation board at (membership required). You can also visit the company’s website or contact the company by e-mail:

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

2012-07-31 n/a 11148 Insulated Storm Windows?

Can top energy performance be achieved by combining fairly standard windows with really good storm windows or even a second set of prime windows?

A low-e storm window at my colleague Peter Yost's house in Brattleboro. Click on image to enlarge.
Photo Credit: Peter Yost

I’ve done a lot of digging into window options in the past few months—not only for a special report on windows that BuildingGreen published, but also for the renovation of the early-19th-Century farmhouse that my wife and I recently purchased.

The state-of-the-art with windows in terms of energy performance and quality is clearly seen in the triple-glazed European windows that are certified by the Passivhaus Institut in Germany. You can now buy these wonderful windows with unit center-of-glass R-values above R-9 yet high-enough light transmission to work well for passive solar houses (solar heat gain coefficient above 0.60).

The problem is that these windows are incredibly expensive—some over $100 per square foot, which comes to $1,500 for a typical 3' x 5' window. You get a lot for that price in the way of top-quality materials, construction detailing, durability, thermal breaks, air tightness, and energy performance, but the windows are simply way above the budget range for most projects. Furthermore, replacing existing windows is often very hard to justify unless the existing windows are in very poor shape.

Insulated-glass storm windows?

As I’ve thought about ways to obtain top-performance windows more affordably, I keep coming back to the idea of installing (or keeping) fairly standard, double-glazed windows—with low-e coating and argon gas-fill—and then installing a much-better-than-usual storm windows.

I’m considering three different options. The first option would be to install a single-glazed, low-e storm window on the exterior of the prime window. The storm would have to have a durable (hard-coat) low-e coating, since it wouldn’t be protected in a sealed air space, as most low-e coatings are. With this configuration I would end up with triple glazing and two low-e coatings in the full assembly. I’m not sure whether these would be old-style storm windows that are installed and removed seasonally, or more sophisticated (and convenient) triple-track or double-track storms with screens.

A second option would involve an insulated (double-glazed) storm window, so that I would end up with quadruple glazing—two insulating glass units (IGUs) separated by an air space. Because no storm window manufacturer (yet) makes such a product, this would likely necessitate custom-made storm windows. I know those can be made, because I’ve seem insulated-glass, low-e storm windows that J.S. Benson Woodworking & Design has produced in the shop next-door to our BuildingGreen office in Brattleboro.

A third option would be to install two sets of insulated-glass prime windows. I’m still working through how this would work—and very much open to suggestions. I could install a double-hung window on the interior and a casement window on the exterior, or I could install two sets of double-hung windows.

I’ll have to think about cleanability of windows with these options; that might be a little challenging with the two prime windows. If I’m going to have two low-e coatings in the window assembly, I also need to figure out whether the temperature reached in the interior IGU might get too high. By trapping a lot of heat it’s possible that the temperature reached by the glazing seal could be higher than the sealants are rated for—in which case I might need to find a window made using silicone seals (as I believe Andersen uses).

If you have experience with such a detail (particularly options two and three), let me know what you did. Or let me know what your thoughts are even if you haven’t tried it. You can post a comment here and share your experience with others or, if you prefer, e-mail me directly.

Looking for new storm windows? Check out our GreenSpec guide to help you find storm windows.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.


2012-07-24 n/a 11100 The Ongoing Revolution in LED Lighting

LED lighting keeps on improving as yet another record efficacy is announced.

Cree's new XLamp XP-G2 LED chip delivers up to 165 lumens per watt. Click on image to enlarge.
Photo Credit: Cree

A few days ago I got yet another press release about a new efficiency record with LED lighting. These are almost commonplace as we ride the revolution that is redefining electric lighting.

To back up, let me provide a short synopsis of lighting technologies and history.

Incandescent lamps provided the first electric lighting, with Thomas Edison inventing the first commercially viable light bulb around 1880 (building on the inventions of many others), and the technology has changed relatively little since General Electric introduced tungsten-filament light bulbs in 1911. Electric current flows through a very thin, coiled filament made of tungsten wire and glows white-hot, producing light. With incandescent lighting, roughly 90% of the electricity is converted into heat, only 10% into light.

Lighting was revolutionized in the 1920s with development of fluorescent lights. With this technology, an electric arc is established in a glass tube filled with mercury vapor. The arc produces ultraviolet light and that light energizes a phosphor coating on the inner surface of the glass tube. That phosphor, in turn, fluoresces, emitting white light.

Various high-intensity discharge (HID) lighting technologies (mercury vapor, high-pressure and low-pressure sodium, and metal halide) also function by energizing mercury vapor, but with other gases that obviate the need for phosphors. Very concentrated light can be generated, which makes this lighting popular for street lights, stadium lighting, and such.

Enter LED Lighting

LED lighting is fundamentally different from incandescent, fluorescent, or HID lighting. LED stands for “light emitting diode.” It is a solid-state device made of a specialized semiconductor material that emits light when energized. The first LED lights were red or green (depending on the semiconductor material) and used primarily as indicator lights on electronic equipment. Blue and other colors came along later. The challenge has long been producing quality white light.

Over the past 10-15 years, developers have figured out ways to either combine different-color LEDs to produce—in aggregate—white light, or to use phosphor coatings to modify the emitted light color, so that we see white.

LED lighting avoids the mercury in fluorescent and HID lighting, and its efficacy (a measure of lighting efficiency in units of lumens of light produced per watt of electricity consumed) is now considerably higher than that of incandescent lighting, and the best LEDs now have higher efficacies than even the leading-edge T-5 fluorescent lamps.

When I first wrote about LED area lighting (as opposed to exit signs) in Environmental Building News back in 2002, I reported a breakthrough in LED performance. A new LED light source had just been introduced by Lumileds that provided a remarkable 24 lumens per watt. That was significantly higher efficacy than that of incandescent light bulbs, but still nowhere near that of fluorescent lamps. In the same article I quoted a researcher at Lumileds saying that he thought LED performance would eventually reach about 100 lumens/watt.

State-of-the-art LED lighting today

The press release I got a few days ago from Cree Lighting (one of the other major producers of LEDs and LED lighting products) reported that their newly introduced XLamp XP-G2 LED provides a remarkable 165 lumens/watt in a cool-white and 145 lumens/watt in warm white (assuming 25°C temperature). Measured at 85°F (accounting for worst-case conditions in a fixture), that XP-G2 efficacy drops about 8%--to 151 and 133 lumens/watt respectively.

Cree's CS18 eight-foot linear LED fixture. Click on image to enlarge.
Photo Credit: Cree.

Once those LEDs are incorporated into actual lighting products, the efficacy drops, but the best LED lamps and light fixtures today using earlier-generation LEDs can still provide well over 100 lumens per watt. Cree’s CS18 eight-foot linear light fixture for commercial buildings, for example, delivers up to 120 lumens/watt.

With smaller LED lamps that can replace incandescent light bulbs, performance isn’t quite up to 100 lumens/watt yet. Philips’ best EnduraLED bulb provides 900 lumens of light (more than a 60-watt incandescent bulb) using just 10 watts of electricity. That’s an efficacy of 90 lumens/watt.

The light quality from LEDs has also steadily improved. Both the Cree CS18 and Philips EnduraLED products mentioned above have a color rendering index (CRI) numbers of 90, which is better than almost any fluorescent lighting available. One of Cree’s LED lamps has a CRI of 93.

LED lights have a very long life. The Cree CS18 is guaranteed for five years and rated for 50,000 hours, while the Philips EnduraLED is rated for 30,000 hours—compared to about 20,000 hours for a typical linear f