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Closing the Feedback Loop

Demand for proof-of-performance claims plus increasing designer confidence lead to a resurgence in evidence-based design.


By Nadav Malin

Designers and owners rarely take the time to understand how well their buildings actually perform. Those who do typically engage in some form of post-occupancy evaluation (POE). A POE, also known as a building performance evaluation, explores both objective performance metrics, such as energy use, and the subjective experiences of the occupants, through occupant surveys and interviews.

Photo courtesy Timothy Hursley
A post-occupancy study revealed that the Seattle Public Library is using significantly less energy and slightly less water than the designers predicted.

Overall building satisfaction scores from the Center for the Built Environment’s occupant survey tool show that LEED and other green buildings tend to score higher than most other buildings in the database.

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When you look at the amount of money that goes into creating a building, there have to be some resources for making sure that it works as intended,” says Rosamund Hyde, of Stantec. Building commissioning is usually thought of in relation to a structure’s systems; a POE, on the other hand, introduces the elusive human factor and addresses the important question of how well a building and its occupants interact. “There is a lot of hype about better buildings, but insufficient evidence to support the claims,” says Judith Heerwagen, an environmental psychologist at J. H. Heerwagen & Associates who focuses on workplace ecology. “I think clients are beginning to say ‘Show me the data.’”

With the release of LEED for New Construction version 2.2, owners are required to survey occupants in order to achieve LEED’s point for thermal comfort. Interest is growing in the U.K. as well, according to POE expert William Bordass of the Usable Buildings Trust. He attributes the growth to concerns about climate change and to a more general “client and government interest in performance outcomes and design quality.”

Those performance outcomes are an essential aspect of any discussion about efficiency, says Charlie Huizenga, a research specialist at the Center for the Built Environment (CBE) of the University of California, Berkeley. “It’s always possible to save energy by turning off lights or adjusting thermostats, but those changes would come at the occupants’ expense,” he says, adding that energy performance numbers should be linked to certain levels of occupant comfort.

Internet-based programs have made it relatively easy and inexpensive to administer occupant surveys and compile results. With support from the U.S. General Services Administration (GSA) and others, CBE researchers have pioneered the use of such programs in the U.S. CBE’s occupant survey tool, the most widely used such program in North America, has technology & innovations that address overall satisfaction with a building, office layout, thermal comfort, air quality, lighting, and acoustics, and can be customized to meet the needs of specific users.

Between expensive, complicated studies funded through special arrangements and quick-and-dirty evaluations that can be done cheaply but that may yield less valuable data, there is a sweet spot for which researchers are aiming. Rosamund Hyde managed a project, funded through the Vancouver, British Columbia–based EcoSmart Foundation, to study six buildings using a fairly comprehensive protocol, and is now working with the project team to streamline that protocol and apply it to a larger set of buildings. However, she notes, “It’s not the price point that we’re looking for, but the right thoroughness point.”

While Hyde’s Building Performance Review project uses CBE’s occupant survey program, New Buildings Institute (NBI) has developed its own survey tool as part of a more accessible performance evaluation, one that would result in cursory, “level one” reviews. This approach is now being pilot tested, and NBI hopes to have a formal POE program available for general use in about a year.

For organizations with large real estate portfolios, such as the GSA, “there is a real business value to doing POEs because they can use what they learn from them to validate or change their approach,” notes Heerwagen. In other organizations, POEs are conducted only if a designer or owner is dedicated enough to invest in learning from a completed project. As the cost of POEs comes down and the pressure to show results grows, more and more projects will be getting the attention they deserve.

Graph, courtesy of Center for the Built Environment at UC Berkeley

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This article appeared in the January 2007 print issue of GreenSource Magazine.

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