LEED Buildings: How energy efficient are they? - Part II

After reflecting for a few weeks on my last post, I did a bit more research. I received a bit of feedback for and against the comments expressed by Mr. Gifford and I wanted to take a step back with a more impartial look at th energy consumption data analyzed by the NBI study. As is usually the case, I "stumbled" upon the information I was looking for (there are many others out there with the same questions as myself) in another study recently published in Energy and Buildings Journal which specifically reanalyzes the data used in the New Buildings Institute LEED study which was so heavily scrutinized.

The study, appropriately titled "Do LEED-certified buildings save energy? Yes, but..." was completed by a group from the National Research Council Canada in Ottawa. The team did a very thorough and more scientific analysis of the data, carefully outlining the conclusions made by the NBI, the complaints made regarding the presentation of such data (by Gifford and others) and the reasoning and methodology behind the new analysis. All of these effort are especially important to clarify the "motivation" and transparency of the report - which I found to be more dependable than previous analysis.

To spare you the details, the report found three main conclusions (color-coding for dramatic effect):

1. On average, LEED buildings use 18–39% less energy per floor area than their conventional counterparts.
2. However, 28–35% of LEED buildings use more energy than their conventional counterparts. 
3. Further, the measured energy performance of LEED buildings has little correlation with certification level of the building, or the number of energy credits achieved by the building at design time.

The study further goes on to state: "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."

I would like to clarify that I want to emphasize the critical views of LEED not because I want to discredit its system or intent, but to bring to light where improvements can be made. The system is not perfect and there are obviously flaws which need to be addressed in order for LEED buildings to actually make an impact on building energy consumption!

Even though it isn't directly mentioned, this study summarizes what almost everyone in the building industry realizes: Green design is only one part of the equation; construction practices and actual operations and maintenance are the real indicators of efficient energy consumption.