I keep hearing that many LEED certified buildings actually burn more energy than those that claim no “green” status. While studying for the LEED AP exam, I came across at least one obvious reason for the energy glut of buildings prizing a LEED certification and thought I would share it here.
For those of you who don’t already know, Leadership in Energy and Environmental Design (LEED) is a rating system where points or credits are earned by complying with various criteria set forth by the United States Green Building Council (USGBC). A building earns a Bronze, Silver, Gold or Platinum Certification depending on how many credits earned.
So here is where some of the excessive energy consumption may be coming from. In the Indoor Environmental Quality section of the LEED rating system, one credit can be obtained by increasing the ventilation rate in the building, or in other words, increasing the amount of indoor air that is replaced with fresh outdoor air within a certain period of time. An increase of at least 30% above the minimum standard is required to earn this credit for buildings that are mechanically ventilated. Buildings implementing natural ventilation techniques (i.e. operable windows, stack effect, thermal mass, etc) must follow a different set of criteria for increasing ventilation levels to earn this credit. I won’t get into that here, since I am more concerned with the cause of the increased energy consumption and most natural ventilation techniques do not consume any energy. But as you have probably already guessed, increased ventilation rates in a mechanically ventilated building results in increased energy consumption.
Additional air ventilation improves the indoor air quality of the building and improves the comfort of its occupants. According to the U.S. Environmental Protection Agency, indoor pollutant levels are sometimes 2-5 times and occasionally even as high as 100 times more than outdoor pollutant levels. So I can see why increased ventilation should be integral to the design of an environmentally responsible structure.
But on the other hand, according to the U.S. Department of Energy, buildings consume about 37% of the energy produced in the United States, making the reduction of a building’s energy consumption, in my opinion, a high priority on the journey towards sustainability. The fact that many supposedly green buildings are actually heading in the wrong direction is quite shocking.
Although additional ventilation is nice, the USGBC should disqualify mechanical ventilation as a viable option to increase ventilation. Instead, they should require mechanically ventilated buildings to compliment their HVAC systems with natural ventilation techniques when possible, to increase ventilation and earn this credit without increasing their energy consumption. Besides, most people prefer opening a window than having a vent blasting air in their face anyways.
That being said, a measly one point earned for increasing ventilation hardly seems like it could be the sole culprit for the higher energy consumption of LEED buildings. So here are some useful links if you want to read more about the questionable energy efficiency of LEED Certified buildings:
For more information about USGBC and the LEED Rating System go to www.usgbc.com.