Verifying Performance with Building Enclosure Commissioning
By Paula Melton
It’s mist! It’s smoke! It’s a low-lying cloud!
In fact, the eerie fog pouring from under the soffits of a newly built elementary school on a U.S. military base was just the disappointing result of an air-barrier test. Although the U.S. Army Corps of Engineers (USACE) has required performance testing of air barriers in all its construction contracts since 2007, the final results are not always satisfactory. And with this particular school building, the stage was not
set for success, explained Matthew Heron, P.E., department manager of Pie Consulting & Engineering’s building science group. That’s why consultants like Pie are increasingly offering—and owners like USACE and many contractors and architecture firms are increasingly seeking out—building enclosure commissioning, or BECx.
Cx vs. BECx
“A lot of people think commissioning equals testing,” says Heron. “But it’s not a test at the end. To be successful in a test is to have involvement way before that.” Every stage of design and construction should be covered.
Although BECx—also known as building envelope commissioning—is already showing up in more federal contracts and being codified in standards, including LEED (see below), many architects and contractors are unfamiliar with the process of fundamental commissioning they’ve grown used to—which has traditionally focused on mechanical systems and other controls. And while the best commissioning processes should begin during the earliest stages of design, with the building enclosure, it’s more of a “must” than a “should.”
Commissioning began in naval yards, explains Rob Kistler, AIA, principal at The Facade Group and vice chair of the Building Enclosure Technology and Environmental Council—the committee in charge of updating the National Institute of Building Sciences’ (NIBS) Guideline 3 on building enclosure commissioning. “It started with slapping a bottle of champagne on a boat,” he told EBN. The boat “slides down into the water, and if it floats, it’s been commissioned, and it’s given a name.” But with building systems (as with modern naval ships), there’s a lot more to commissioning than “Does it float?”
Kistler claims that commissioning the envelope is even more complex than commissioning most other building systems. With mechanical system commissioning, he argues, “You’ve got machines that are built in factories, tested and verified in the factory that they can meet certain performance requirements.” They are packaged and shipped in working order and built to create a mechanical plant. “What you’ve got to do is tune all those pieces together; if you don’t tune all of those, you have losses in the system.” Yes, very sophisticated engineering may be needed up front, and things do go wrong with both the equipment and the distribution systems like ducts and registers, but for the most part that system can be tuned after construction, he points out: “You can actually go in and turn some knobs and turn some dials and make this thing hum.”
Not so with the building envelope. “The building enclosure is built by thousands of people on the site, piece by piece, with nothing that says it can perform,” he says. “The membranes we use are made with specific performance requirements, but if you don’t put it on right, it’s not going to perform.” Moreover, if you find problems after construction, they are likely sandwiched somewhere between the exterior cladding and the interior finishes, meaning that assemblies have to be torn apart and rebuilt. “You need to start early with the design process to make sure the systems you’re trying to design at least have a chance of working together.”
Envelope parts that work together can save everyone pain—and possibly legal trouble—after occupancy. “The building envelope is a very high-risk piece of construction,” says Heron. “Something like two-thirds of litigation has to do with moisture in buildings. Commissioning helps mitigate the risk.”
Toward whole-building commissioning
Although complexity of systems does vary, BECx works best as part of a whole-building commissioning process. “Building enclosure commissioning and mechanical system commissioning go hand in hand,” says Elizabeth Cassin, R.A., senior associate at Wiss, Janney, Elstner Associates. Mechanical system sizing and design are based on assumptions about building envelope performance, and if those assumptions don’t become reality, energy goals and occupant comfort are far less likely to be achieved. Cassin adds, “If your enclosure doesn’t work, then a lot of times your mechanical system can’t be balanced.”
As with other types of commissioning, the precise scope of BECx varies according to the scale of the project and the owner’s and project team’s needs and goals. However, “there’s a minimum scope of work for it to be considered commissioning,” says Cassin. “If you’re only doing a test here or there, we don’t consider that commissioning an enclosure.”
Here’s what you can expect from a typical BECx process at each stage of a project.
According to building envelope specialists, architects, and owners who have been through it, a collaborative approach to BECx fits readily into projects using integrated design, integrated project delivery (IPD), or design-build contracts. During pre-design, the BECx team typically contributes to initial budget estimates and provides third-party expertise regarding the most appropriate building envelope materials and assemblies, what types of testing may need to be done, and how targets like energy performance or building longevity can best be achieved within budget limitations.
This participation is crucial, Kistler argues, in part because it helps provide early-stage “value engineering” in the best sense of the term. “Making sure they are using systems that are economically appropriate for that building type or intent” is part of the point of enclosure commissioning “so the building contractor doesn’t come back and say you can’t afford that.” When they receive a budgetary reality check up front, architects are less likely to end up “questioning all [their] design decisions to figure out, Does this substitution work?”
Early involvement also helps prepare the project team to provide a different standard of design and workmanship than they are probably used to: all the building enclosure’s systems—from thermal insulation to air barriers, fire breaks, mechanical services that penetrate the envelope, and any number of other functions—have to be integrated. And that integration needs to be explicitly laid out for contractors. “For architects, it’s taking drawings beyond looking pretty, and looking at the technical side of it,” says Cassin. “You really have to design your air barrier—not just put a line in your spec that says ‘make air barrier continuous.’”
Drawing reviews are a critical part of BECx for good reason: although awareness is growing, the importance of continuity, particularly as it relates to moisture management, has not yet caught on widely across the industry (see “,” EBN Nov. 2012). Brian Eason, AIA, project architect and senior vice president at HKS in Dallas, is working on his first project using BECx right now—a USACE design-build contract on the campus of Darnall Army Medical Center in Fort Hood, Texas. As part of the process, he’s been asked to provide drawings that “connect a line all over the building to see if I can run one single line in plan and in section” showing a continuous air barrier. Eason says he’s never been asked to do that before, and he admits, “It’s probably going to show me some holes.”
“The word ‘continuity’ is something we use a ton,” says Heron. “Continuity between transitions is where we spend just about all of our time, both in design and in construction.” Wherever there are plane changes, wherever walls meet roofs or cladding types come together, there are opportunities for discontinuity. “We’re more often seeing self-adhered underlayment” on roofs, he explained. “It offers great air control, but tying that into the wall is a real challenge.” He says they are constantly asking architects, “Where is your plane of airtightness? Where is your plane of moisture control?”
Kistler concurs. “I’ll spend 20 to 40 hours reviewing drawings,” he said. “That’s a lot of time. But in that process, we find a lot of issues that are picked up by somebody on paper—and when the guy gets to the field, he has the information he needs.” The issues Kistler finds during drawing reviews run the gamut from the most frequent and most typical (incomplete air barriers and moisture membranes) to the incomprehensible (no air barrier, no membrane) to intriguing hybrids. “I’ve seen WRBs [weather-resistive barriers] or membranes joined one way on the sill and the other way on the jamb,” he told EBN. “I’ve seen a curtainwall system shown in plan and a storefront system in section. They’re just totally different systems; you can’t do this.” On the more bizarre end of the spectrum, “I’ve seen somebody who added a nail flange to a curtainwall,” he continued. “I’ve seen people draw membranes right through concrete: the membrane goes right through the concrete and comes out the other side.”
Part of the problem, in his view, is that architects may think they are providing adequate drawings in 3-D models, when in fact these models are not powerful enough to deal with drawing a true sectional detail. “Successful people take it down to 2-D,” he said.
Neither Heron, Kistler, nor Cassin has observed that more scrupulous detail work is being more widely adopted yet. “It’s all over the map,” Cassin told EBN. Although a few architects are providing meticulously integrated thermal, air, and moisture barrier details, many more are sticking with the older ways.
“There’s not necessarily a consensus on the level of detail that should be done, even in 2-D,” says Heron. “Some folks take it so far that the wall section is generic-looking details” and then at each transition they simply say, “From here forward use manufacturers’ standard details. That usually doesn’t work in all situations, even in a relatively simple building.”
If adopted more widely, BECx could help drive mainstream architectural practice toward more detailed section drawings. But there are other pressures at work too. “The topic of architects’ fees also plays a role,” Heron says. “I’ve had conversations with architects who would love to be detailing to that level. But fees for projects are going down. Something has to give.”
During construction, enclosure commissioning includes testing and training before envelope construction begins, spot-checking workmanship on the jobsite, and pre-occupancy testing of installed assemblies.
Maybe there’s something inherently fun about spraying stuff with hoses; of all the stages of BECx, people seem to remember building and field-testing mockups most vividly. Testing mockups serves many needs during the commissioning process.
Identifies weak points in assembly design. Window, storefront, and curtainwall assemblies are commonly tested for water leakage—and water leakage is often found. This small-scale testing may result in assembly re-design, specification of more compatible materials, or a clearer understanding of how the materials ought to be applied or installed. Although water resistance and structural integrity are often the focus, the Darnall Army Medical Center project will even include an enclosed mockup to do preliminary air-barrier testing as well.
Establishes the most efficient construction sequencing. Often, problems identified during mockup testing can be addressed by applying materials in a different order. Mockups help the general contractor develop a more accurate sense of the proper sequencing to provide good envelope performance, and this can save everyone time and money. “The air barrier and how you get it into the building is changing the way contractors build buildings,” explains Kistler. If the sequence isn’t clear both in drawings and after mockups, “the contractor is putting stuff together and it doesn’t go together; then you’ve got 20 people standing around with their hands in their pockets, and you have to take it all back out. That’s all lost money.”
Helps train the construction crew. Both successes and failures during mockup testing help provide information about appropriate materials and sequencing. Proper installation techniques can then be shared in detail with construction workers, subcontractors, and quality control specialists, increasing the chances that meticulous workmanship will follow from meticulous design.
“They really worked with the contractors specifically as the construction side of things got going,” says Nicholas Alexander, project engineer at USACE, of his first experience with building enclosure commissioning. As an owner, a certified Passive House consultant, and the primary developer of the Corps’ stringent air-barrier testing standard, Alexander was impressed with how the process helped deliver a high-performing dining hall at Fort Carson in Colorado. With an air leakage rate that he said far exceeds the expectations of the Passive House standard, the dining hall is also certified LEED Gold and achieved an innovation credit for building enclosure commissioning. Alexander credits the hands-on approach of the BECx consultant, Pie.
“They were out there frequently, inspecting the project, walking around with the QC [quality control manager],” said Alexander. “They brought out several product reps to inspect manufacturer-specific products. They were out doing their own specific inspections of the building insulation, the air barrier, the moisture barrier seals around windows and doors—things like that.”
Ideally, those jobsite inspections won’t result in assemblies having to be disassembled—though that does happen. “A lot of people have to do their jobs right,” says Matthew Heron. “A reputable firm will do two things. You’re out there looking at whether things are not installed right,” but also, “a separate piece is being able to look down the line and help avoid problems that are about to happen.” Pie, he says, takes more of a “collaborative approach” rather than trying to monitor the application of every bead of sealant: after all, it’s in the contractor’s best interest to get things right the first time. “They don’t want to be called back nine months later because there’s something wrong.”
Field testing during and just after construction is another of the more memorable parts of enclosure commissioning, and like mockup testing, it tends to be what people think of as “commissioning.” Without a lot of work leading up to the series of stresses the envelope has to take, though, the project is unlikely to get high marks on these tests.
“I’ve seen a lot of air barrier tests,” says Alexander, “and I think the whole building enclosure commissioning process is a huge value added to the Army projects that we do—and just generally.” Not all the air-barrier tests go well. “We have had some failures,” he told EBN. Although only two buildings have “not been able to be reworked to the point of passing,” he says, “they have all required rework and relatively expensive repairs.” By specifying BECx more commonly in the future, Alexander hopes to avoid such failures.
What gets tested
NIBS Guideline 3 is 337 pages long—and Annex U, on field-testing procedures for everything from whole wall and roof assemblies to expansion joints, shingles, and gutters, takes up 53 of those pages. How do you decide what to test?
That, of course, depends on specific performance goals, but the BECx process is moving increasingly toward assessing hygrothermal performance, or the interplay of heat and moisture. Tests are likely to follow any of numerous ASTM procedures that focus on the continuity of thermal insulation as well as climate- and site-specific risks, such as bulk water leaks from wind-driven rain, or condensation that might be caused by thermal bridging or air leakage.
Even after BECx has verified that the building is snugly wrapped up in continuous air, thermal, and moisture barriers, the process is not quite complete: as with fundamental commissioning, enclosure commissioning helps ensure that inspection and maintenance plans are in place for the enclosure and that documentation like warranties and manuals for building envelope products are handed over to the owner. Ideally, post-occupancy walkthroughs will include the BECx team as well.
Who Needs It?
Right now, BECx is being used primarily for large federal building projects; in the private sector, universities, hospitals, and other owners with a focus on durability are starting to include it in contracts as well.
As a BECx specialist and developer of NIBS Guideline 3, Rob Kistler believes that building enclosure commissioning is valuable for every project, regardless of type and size. “It’s just a mechanism of giving assurance that the system will perform to the level of performance you thought you were going to get when you started the process,” he explained. But project scope and budget will naturally affect the scope and budget of commissioning, and some project types definitely need more intensive review and testing than others. “If you are using a lot of off-the-shelf materials and well-known systems, you will still want to do some testing, but how much is up to the owner,” Kistler explains.
Sometimes the stakes are very high. Pointing to the recent deaths from meningitis caused by fungal growth in medications from a Massachusetts laboratory, Kistler argued that the need for BECx goes up dramatically as the risk posed by moisture problems increases. “You really don’t want mold in the walls in a hospital; the issues with that go beyond mold in the walls in your house,” he said. Similarly, “if you get a water leak in the roof of a data center that drops into the computers below, the money they lose from having a leak in the roof is huge.”
Regardless of which system is being commissioned, “the commissioning agent ideally would work directly for the owner,” says Gerald Kettler, P.E., managing principal at Facility Performance Associates and chair of the project committee for the recently released ASHRAE Standard 202, Commissioning Process for Buildings and Systems. “The commissioning authority is the technical resource for the owner. That’s what the commissioning process does—makes sure the owner gets what he’s paying for.”
In practice, the BECx team may not work directly for the owner—at least contractually. Does that mean a consultant hired by an architect or general contractor as a commissioning agent isn’t really doing commissioning?
Right now, no, Kettler says. “The preference is for independence, but a lot of owners don’t want a separate contract. They go to the architect and say, ‘Go find me a commissioning authority. Don’t make me pay another bill at the end of the month.’” These contractual issues could, in theory, result in conflicts of interest. Elizabeth Cassin has done BECx for several federal projects, and her firm has always been hired directly by the owner. “I would hope that helps [the project team] understand that we have the best interests of the owner in mind, and we’re not trying to look out for any of the other parties’ interests. It’s really in the end the user that we’re helping.”
In practice, says Matthew Heron, contractual niceties don’t make much difference. A colleague has quipped, “I work for the building,” Heron told EBN. “I like that line, and I share that line. In the federal and military world, the Army Corps is heavily reliant on design-build. Commissioning is the responsibility of the design-builder.” With the U.S. General Services Administration, though, “more often than not, you’re working purely for the owner.” Heron is much more concerned about ensuring that BECx is done by a third party than he is about who signs the papers; it concerns him more when firms do internal drawing reviews, field tests, or quality control and try to pass that off as commissioning.
Kistler sees a trend toward direct hiring by owners, primarily due to a game of budgetary whack-a-mole. “Design fees are being cut,” he explains, so his firm is far less likely to be hired by the architecture firm as a building envelope consultant. “But if I go to the owner and tell the owner, ‘You need someone to commission this building,’ the owner will hire me.” But whether the building enclosure specialist gets paid as a design consultant or as a commissioning agent, he argues, the building owner needs to bite the bullet and pay someone to do the job. “The issue comes back to not having enough money to build the building to begin with, hammering people down on their bids. Six to eight years from now, they’ll be in court with less durable buildings.”
It’s likely these contractual issues will be refined as whole-building commissioning sees wider awareness and adoption.
Cost vs. Value
When the U.S. Green Building Council (USGBC) first introduced the idea of building enclosure commissioning as a LEED prerequisite (more on that below), the decision was widely protested—not because the green building community objected to the concept but rather because they feared clients wouldn’t pursue LEED certification because of increased costs. Although it’s a small sliver of the overall budget (NIBS Guideline 3 estimates 0.3%–1%), BECx—done right—does come with a significant price tag, typically tens of thousands of dollars. Will clients go for that?
“A lot of us in the industry say commissioning doesn’t cost: it pays,” says Gerald Kettler. “What happens on a building that is not tested or commissioned is that you end up with a product from a construction standpoint that doesn’t work as the designer and owner intended it to work.” That can result in multiple drains on the building owner’s bank account, from a constant trickle caused by mechanical systems (and uncomfortable employees) that aren’t working efficiently to massive payouts for envelope or equipment repairs due to air or water leaks.
BECx can even save the owner money up front, Heron explains. “Air leakage in buildings is a significant contributor to HVAC loads, impacting the sizing of the HVAC systems. So there is the first-cost piece in new construction and the performance piece.” The same goes for continuous thermal insulation.
As Nicholas Alexander at USACE puts it, “If we don’t have an enclosed space, we don’t have a building. It’s the most reasonable place to make improvements with minimal cost and not a whole lot of risk.” He adds that for federal projects, “it is a taxpayer-friendly approach to improving the overall sustainability of a building. The enclosure is the one aspect of the building that for all of the history of the built environment has never been really effectively engineered. It is really just fundamental to a sustainable building.”
Contractors and architects, too, are finding value in BECx and are more frequently recommending it to owners as a check on their own internal processes. “If you find one hole in testing, it might have cost the contractor $500 to do that test,” says Kistler. “What if the owner found it a year later with a leak on the floor? That 500 will probably have several zeroes on it. That’s where the savings come from.” Unfortunately, convincing contractors and building owners alike can be hard. The “pay me $100,000, and if you don’t pay me it’ll cost you half a million” argument doesn’t work for everyone.
With the popularity of enclosure commissioning on the rise, there is a temptation for firms to compete for that business with very low bids. How are they providing BECx at such low prices?
A group it almost always works for? The once-bitten. “People who’ve lived through a major issue on a building are very receptive to having an enclosure consultant,” Kistler relates. “Everybody loses in that battle, once you end up with some kind of enclosure leak. The money is huge. You’re going to pay your attorney more than you would have paid the [envelope] consultant.”
BECx on the cheap
They’re not, says Kistler. “You’ve got people who are trying to commission the building enclosure, and they think they can go out and do a test,” he says. “You don’t want to do the tests; you want to look at how the guy puts the stuff on the wall. If you don’t do the piece up front, I don’t think you’re doing the service to the owner. If the owner chooses only to do the test at the end, he’s doing a disservice to himself.”
One of the reasons Kistler got involved in development of NIBS Guideline 3 was his desire to ensure that BECx is performed thoroughly; he’s already seeing people claiming to do enclosure commissioning that’s not the real deal, and he doesn’t mince words: “They don’t have a clue what they’re doing.” Even with mechanical commissioning, sometimes “at the end of the day the building doesn’t perform. So you hire another person who comes in and says he didn’t do this, he didn’t do this, he didn’t do this.” Kistler doesn’t blame any one person or firm for this—the system effectively incentivizes shoddy workmanship from everyone—but he does lament that this is “where the industry drives itself.”
Where is BECx going from here? “It’s going to explode,” says Rob Kistler, adding that many commissioning firms are hiring enclosure specialists.
USACE’s Nicholas Alexander believes BECx is “the wave of the future,” and industry metrics appear to agree. According to a survey of commissioning providers by trade group AABC Commissioning Group, the building enclosure was included in 15% of commissioned projects in 2012, up from 9% in 2011, and these firms expect that number to continue rising.
But the experts also continue to emphasize the importance of sticking to high standards and ensuring quality work throughout the entire project. “Ultimately what we want is durable, energy-efficient buildings,” says Kistler. “Adding another person in the line doesn’t guarantee that. My fear is that it’s going to go the way of most of the rest of it, and the value to the owner will be diminished.” With clearer mandates about what is required—as well as owners’ willingness to pay full price in order to receive full value—the growth of building enclosure commissioning could help ensure that more and more of our high-performance buildings truly perform as they should.