LEED buildings show mixed results
June 15, 2009
By Canadian Consulting Engineer
A just released report on the post-occupancy performance of LEED-certified buildings has reached some surprising co...
A just released report on the post-occupancy performance of LEED-certified buildings has reached some surprising conclusions.
The report by G.R. Newsham, S. Mancini and B. Birt of the National Research Council of Canada’s Institute for Research in Construction is entitled “Do LEED-certified buildings save energy? Yes, but …” (Ref. NRCCC-51142).
The authors used measured data from 100 LEED-certified commercial and institutional buildings in the U.S. and compared their energy use to that of the “general stock” of counterpart buildings in the U.S.
The good news was they found that on average LEED-certified buildings used between 18% to 39% less energy per floor area than their conventional counterparts.
The bad news was that 28-35% of the LEED-certified buildings used more energy than their conventional counterparts.
Moreover, they found that there was little correlation between the energy performance of a building and the LEED certification level (Platinum/Gold, Silver or Certified). Nor did the buildings’ measured performance correlate with the number of energy credits it scored based on the design.
The authors conclude: “Therefore, at a societal level, green buildings can contribute substantial energy savings, but further work needs to be done to define green building rating schemes to ensure more consistent success at the individual building level.”
They also add a proviso: “Note, these findings should be considered as preliminary, and the analyses should be repeated when longer data histories from a larger sample of green buildings [is] available.” They point out that the conclusions were drawn from data drawn during the early years of operation “when ‘teething problems’ or unusual start-up operations will inevitably occur.”
They also point out that the results show the importance of investigating the post-occupancy performance of buildings, saying, “There is clearly no meaningful way to refine green building rating schemes so that they become more reliable without measured performance data.”
The study was based on a re-analysis of data supplied by the New Buildings Institute and the US Green Buildings Council.
The work was partly supported by the Program of Energy Research and Development/Natural Resources Canada.