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Rob Watson recently published "Green Building Market & Impact Report," his second annual report on the impact LEED is having in addressing environmental problems. The report highlights the continuing remarkable expansion of LEED: 2009 registrations for new design and construction projects in the U.S. may actually exceed total new construction starts! (This is possible because projects don't typically register when they start construction, and a flurry of projects were registered just before the requirement to use LEED 2009 kicked in, to keep their options open.) Watson takes note of the shift from whole building construction to Commercial Interior tenant fit-outs (CI) and Existing Buildings: Operations & Maintenance (EBOM) registration and certification. And he compares 2009 certifications to registration numbers from 2006 and 2007 to see what fraction of projects are making it through the system. (In this analysis he assumes a three-year registration-to-certification timeframe for all except LEED-CI projects, for which he assumes two years. I would have given EBOM projects a shorter turn-around as well — in our market analysis for LEEDuser we assumed 18 months.) Analyzing certification and registration trends is not Watson's main point, however. His focus is on the environmental benefits that follow. And that focus is what really caught my attention. I'm thankful he's taken that on, because it's so easy to forget what LEED was created for in the first place. So, how is LEED doing at achieving its original goal? Watson explores this question category by category, looking at numbers of projects in each of the various rating systems that have achieved certain credits. Through 2009, for example, he credits LEED projects with 780 million avoided vehicle miles traveled (VMT) and 15 billion gallons of water saved. He finds that operating energy use in 2009 led to CO2 emissions reductions of 2.9 million tons. He then extends these estimates to 2020 and 2030, with magnified results. Watson's overall conclusion — at least in terms of carbon emission reductions — is that LEED is effective but is not going far enough to help head off a climate crisis. In reaching this assessment Watson does take time to address accusations that LEED buildings may not be saving any energy at all — that debate was covered in detail in a previous post. His arguments are unlikely to win over the skeptics — but that's a tough thing to do. In producing this report he has had to radically oversimplify the analyses, any one of which could easily become fodder for more than one doctoral thesis. And it's worth noting that, as the "father of LEED," he's hardly the most unbiased of analysts one could pick to take this on. But he cares enough to do it and is willing to put out numbers for others to react to, both of which are worth a lot. Looking at the specific analyses, I think he has managed to radically overstate the impact of LEED and radically understate it. Yes, both. At the same time. Whether or not the two cancel each other out to make his estimates valid — well, we'll have to wait for those doctoral candidates to sort that out. The Overstatement The report overstates the impact of LEED because it attributes to LEED the environmental benefit of a project having achieved a certain point, without exploring the question of whether or not LEED actually contributed to that decision, choice, or action. For example, lots of LEED buildings are in urban centers, where they get points for being located near public transit and basic services. Watson associates those points with reduced vehicle miles traveled, which is the intent of those credits. But wouldn't most of those projects have been in those locations regardless of whether or not they pursued LEED? The only way I can think of to correct for this assumption would be to interview a representative sampling of LEED project teams about their decision-making process for each credit, and find out which points were actually affected by their decision to go for LEED certification. To some extent this is a matter of semantics. In talking about reduced VMT and water use, Watson refers to the "savings from LEED," but in discussing operation energy savings he refers to the benefits "from LEED buildings." The latter is less presumptive, because it doesn't imply that LEED itself is responsible for all those benefits. The Understatement Watson describes a few assumptions he's made to keep his projections on the conservative side. But there are some others that he doesn't mention, such as the number of buildings that are built to LEED standards that never sign up with GBCI. The report does include a factor for "built-to-LEED" projects, but Watson only includes in this category buildings that are registered but don't reach certification — about 30% of the total. (My guess is that many of those registered-but-not-certified projects never get built at all.) There is a much larger group of projects that use LEED as a design and construction guide, either at the request of the owner or to meet government regulations. How well these projects actually follow LEED and ultimately perform is anyone's guess, but there are a lot of them and they must have some benefits. Even more significant, but harder to quantify, is LEED's market transformation impact. LEED is not affecting just individual buildings. It is educating and inspiring project teams, leading to more aggressive energy and environmental codes, and generally having an impact on the way all buildings are built (at least in some locales). Watson's report doesn't try to factor in these secondary benefits of LEED. I don't know how one might do that, but I suspect that they're huge. In Conclusion There are many places where a more nuanced analysis would be helpful. For example, Watson describes the growing evidence that workers in green buildings are more comfortable, and conservatively assumes a 1%–2% productivity gain. But other studies have indicated that these benefits are most strongly correlated with daylighting and increased ventilation, which are not achieved as often in EBOM projects as in the others — so assuming those benefits in the rapidly increasing EBOM-certified space is something that needs a closer look. Ultimately, even though the report quantifies a range of benefits, I don't think it intends for those numbers to be taken too literally. The report represents the results of a thought exercise about how LEED is doing at accomplishing what it set out to do. And that's a great thing, because it gets us all thinking about the things that LEED was created to address in the first place.

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1 Thanks for the post. I like posted by Bill Swanson on 12/02/2009 at 10:34 am

Thanks for the post. I like reviewing data like this. Some questions came to mind while reading the energy section.

Page 23, in the comparison of office spaces by size. Is the CBECS data of all office buildings or of office buildings constructed after 2000? If all of the LEED buildings are built after 2000 then we should compare with CBECS buildings constructed after 2000.

The data for the LEED buildings still seems to be based on the voluntary NBI study of 2006. (Why is this the only report of its kind in 9 years?) Is it fair to consider data voluntarily submitted as an accurate representation of the average of the LEED building population? If a building owner is embarassed by thier energy usage they may not respond to the study. If a building owner does not have the means to measure energy use are they as likely to stay vigilant in their energy savings. Is it fair to compare a voluntarily submitted data set with a random sample data set? It's like asking a classroom of children 'who would like the share their grades with everyone' and then comparing the grades of those volunters with the grades of the school as a whole, and basing the teacher's performance on that comparison.

2 Nadav, great review of the re posted by Jameson Detweiler on 12/11/2009 at 10:31 am

Nadav, great review of the report.

I was thinking "The Overstatement" and the fact that the intent behind many LEED credits would have been achieved regardless of whether or not they pursued LEED certification. I think there may actually be a simplified way to address this problem.

I think you can make reasonable assumptions about which credits were previously attended based on the location of the project and the type of building. (This is obviously a generalization, but one which I would suspect would be consistently correct.) From there, you could remove those credits from any analysis. We've got LEED credit data stored in such a way that it would actually be pretty easy to remove those credits based on building type and location and then generate a report from it to see which credit intents LEED actually had a significant influence on.

My 2 cents. I'm hoping we'll be able to use the data we have to increase the accuracy of reports such as these.

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