Feature Article

Whole-Building Life-Cycle Assessment: Taking the Measure of a Green Building

Why we will never understand the true impact of our buildings-and how we should try to anyway

April 29, 2013

The project team for the CIRS building chose a 100% heavy timber structure in pursuit of negative embodied carbon. That target required life-cycle assessment throughout design.

Photo: Martin Tessler, Courtesy: Perkins+Will

“All models are wrong, but some are useful.”
– G.E.P. Box

Net-zero energy use is a difficult goal for most buildings—but it wasn’t nearly enough for the designers of the Center for Interactive Research on Sustainability (CIRS) at the University of British Columbia. First conceived of in 1999 as a regenerative design project, CIRS was targeting net-positive operational energy, carbon, and water quality as well as net-positive embodied carbon.

When design began in earnest in 2008, “the construction carbon footprint became formally one of the aspects that the team was looking at,” explains Max Richter, architect at Perkins+Will in Vancouver. With net-positive embodied carbon as a driving goal, he says, “you have to use life-cycle assessment as a tool throughout your process.”

The team used life-cycle assessment (LCA) three times—first to compare structural systems, second to compare cladding systems, and finally to assess whole-building impacts after construction. “You have to accept the fact that it’s not going to be perfectly accurate,” Richter says. “We don’t look at the calculation that’s coming out as exact down to the last gram of carbon that’s been emitted or stored in the building, but it gives us a picture of how it’s performing.” And, he emphasizes, “It does give you a better picture than if you weren’t doing it at all.”

Richter’s sentiments echo those not only of LCA newbies but also of many experts in the field: although whole-building LCA can be a powerful design tool, it’s important to recognize its serious limitations. Some of these limitations are likely temporary, but others are inherent to the methodology and will never go away.