As more and more building energy data become available a consistent picture is emerging that shows that LEED-certified buildings use no less primary energy than other buildings. The latest contribution in this area is a paper soon to be published in Energy and Buildings entitled, “Energy Performance of LEED-Certified Buildings from 2015 Chicago Benchmarking Data.” This paper compares the annual energy use and green house gas emission for some 130 LEED-certified commercial buildings in Chicago with that of other Chicago buildings in 2015. Chicago, it turns out, has one of the highest rates of LEED-certification among major U.S. cities.
The data clearly show that the source energy used by LEED-certified offices, K-12 Schools, and multifamily housing is no less than that used by other similar Chicago buildings. In the case of K-12 Schools, LEED-certified schools actually use 17% more source energy than other schools!
Many studies that address building energy use only discuss energy used on site, called site energy. We found that LEED-certified buildings in Chicago use about 10% less energy on site than do other similar buildings. No doubt green building advocates will emphasize this apparent energy savings.
But energy used on site – called site energy – is only part of the story. Site energy fails to account for the off-site losses incurred in producing the energy and delivering it to the building – particularly important for electric energy that, on average, is generated and distributed with 33% efficiency. The EPA defines source energy to account for both on- and off-site energy consumption associated with a building; building Energy Star scores are based on source energy consumption. The issue is similar to one encountered when comparing the environmental impact of electric vehicles with internal combustion vehicles — you must trace the energy back to the electric power sector.
How is it that LEED buildings use less energy on-site than other buildings while consuming more source energy? Simple — more of their (indirect) energy use occurs off-site in the electric power sector. They use less natural gas but more electric energy than other buildings. Essentially a larger fraction of their energy use occurs off-site in the electric power sector.
This is the trend in newer buildings, to use more electric energy and less natural gas or district heat energy. Part of this is convenience and part of it is driven by the belief, or rather hope, that the electric power sector will soon be dominated by renewable energy. It is true that the contribution of renewable energy (solar, wind, etc.) in the electric power sector is growing, but this is a very slow process and, for many years to come, natural gas and even coal will remain the dominant source for electricity.
This trend is not unique to LEED buildings — it is present in all new buildings. When you compare Chicago’s LEED buildings with other Chicago buildings of similar vintage you find that they use similar site and source energy.
Bottom line, 2015 Chicago data show that LEED-certified buildings are not providing any significant reduction in energy use or GHG emission.
These results are similar to those observed earlier for LEED-certified buildings in NYC.