On September 10, the prestigious journal Nature published a commentary entitled “Overrated Ratings”, in which it criticizes the LEED green building award system for falling short in promoting design of low-energy buildings.
“…as is well known in the building research community but not outside it,” the editors write, “neither LEED nor any other such rating is a reliable guide to energy performance. Labelled buildings often perform no better in energy terms than the general building stock, and sometimes worse.”
Sometimes WORSE. How is that possible? True, the original LEED system weighted energy performance rather lightly, giving nearly equal weight to site design, water and waste management, and green materials. But these should not be causing the energy use to be occasionally WORSE than average, especially since the energy performance of every LEED building must be modeled if it is to gain energy points.
Here, unfortunately, is the problem, as the editors continue: “most ratings assess a building’s energy performance using theoretical projections from engineers’ models, but don’t measure its real, post-occupancy performance, which often can be much poorer.”
My colleagues and I have just begun work on a project with this exact problem. The building was awarded LEED Gold two years ago, in part through energy points gained with a careful, thorough DOE2.2 model that used the best information available at the time (i.e., pre-occupancy). Two years later, this beautiful building is using about 50% more energy per year than modeled. Fifty percent. This is not the kind of error that results from occupants squeezing a few more people into a space than projected, or cranking the thermostats up a few degrees. This is a sign of pervasive use of building spaces and systems in ways very, very different than intended by the owner, designed by the architects and engineers, and yes, simulated by the modelers.
Why are we doing this? Because, thank goodness, LEED 2.2 had a “Monitoring and Verification” point that this building needed to keep its Gold label. The teeth are sharper in LEED v.3.
We don’t know what the problems are, yet, though we have some preliminary ideas. We believe they will be relatively easy to identify, though we fear that some of them result from conflict between design intents and occupants’ reality. Most of all, though, we hope that this effort will become part of a new, larger, and sustained national effort to evaluate the performance of not just LEED buildings, but all new green buildings, and vast numbers of green-ing existing buildings as well.