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OPINION:
Sustainability Requires Durability

01/2009

By Peter Yost

Green buildings must be durable buildings. If you double the life of a building, no matter what the building is made of, you halve the environmental impact of its construction. But aren’t we building durable green buildings?

To be green and durable and energy efficient, we need a new mantra: manage energy and moisture with equal intensity
Image courtesy Celia Johnson
To be green and durable and energy efficient, we need a new mantra: manage energy and moisture with equal intensity
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Too often the answer is “no,” and too often the problem is moisture. Before the focus on energy conservation that began, for the most part, in the 1970s, a wet building dried quickly because so much heat was blasting through its walls. Now we stuff our walls full of insulation, interrupting that heat flow. That creates the risk that moisture will be trapped in the walls, leading to mold growth, rot, and corrosion. As a result, we get air-quality problems and even structural failures.

I am not saying we need to back off on the energy efficiency of our buildings: green buildings absolutely need to be energy misers. But to be green and durable and energy efficient, we need a new mantra: Manage energy and moisture with equal intensity. And this mantra must be firmly seated on a three-legged stool: quality of design, of materials, and of construction.

It all starts with design. In her groundbreaking book, Designing the Exterior Wall: An Architectural Guide to the Vertical Envelope, Linda Brock exhorts architects to take responsibility for controlling the movement of energy and moisture into and out of buildings:

“This book is written...in the hope that the architectural profession will reclaim design of the building enclosure....Design of the building enclosure is fundamental to the architecture of building. Forfeiting this expertise means losing control of design in general.”

Astoundingly, most versions of LEED are silent on the critical matter of durability and its dependence on the relationship between energy and moisture control. LEED-Canada is an exception, with a Materials & Resources credit for durability, based on the Canadian Standards Association (CSA) S478: Guideline on Durability in Buildings. This standard demands that the expectations for quality be defined for each project, and recognizes the three legs on which that quality stands:

“Durability can be achieved only if: the required quality of design is provided; the required quality of materials is used throughout; the required quality of workmanship is provided throughout construction....”

Residential green-building programs, including the National Association of Homebuilders Green Building Program and the myriad regional and local programs, tend to be a little better on this issue, but most don’t go far enough. LEED for Homes is the only green-building program in the country to have mandatory requirements for both Durability Planning (using a Durability Risk Evaluation Form) and Durability Management (“...builder shall have a quality management process in place to ensure installation of the durability measures”). Jay Hall, then acting Director of LEED for Homes, Ann Edminster, then Chair of LEED for Homes, and I worked for months to get the links among quality, green building, and durability into the LEED for Homes program. I’m proud of that legacy, as it reinforces the case that LEED homes are more valuable—because they’re green and built to last.

It’s not that choosing the best products isn’t important: the debate about using bamboo versus certified maple flooring is a worthy one. However, building professionals need to master building performance as well. With that mastery and our new mantra, we can achieve truly green buildings and maybe even green grace.

Peter Yost is residential program director at BuildingGreen, LLC and technical director for its newest information tool, GreenBuildingAdvisor.com, which features building science-based residential architectural details along with guidance from seasoned experts.

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This article appeared in the January 2009 print issue of GreenSource Magazine.

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