LEED Requires Energy-consumption Data
Nate Gillette, AIA, LEED AP
On June 25, the Washington, D.C.-based U.S. Green Building Council introduced criteria for energy reporting as a precondition for LEED for New Construction certification. The new requirement raises plenty of questions but ultimately shines a light on a hot-button issue for LEED buildings.
The energy-reporting mandate requires energy-performance data for LEED-certified buildings must be supplied to the USGBC on an annual basis or risk losing certification. There are three approved methods prescribed to meet this requirement: signing a release to the USGBC so information can be directly acquired from the utility companies, recertifying the building every two years under LEED for Existing Buildings: Operations and Maintenance, and self-reporting by building owners to the USGBC. The interesting thing to note is there doesn’t seem to be any ramifications for buildings that are performing below their original performance standards. The issue of anonymity of the data also has yet to be discussed by the USGBC.
Energy consumption in LEED buildings has been the elephant in the room. Trying to get actual performance data on buildings is a bit like pulling teeth. Reducing energy consumption in buildings has been a cornerstone of the LEED program since its inception. Why aren’t we talking about it? Doesn’t it make good design sense to compare successes and lessons learned with the collective whole so we can move forward and start making better high-performance buildings?
There is a major disconnect between simulated energy use and actual building performance. This was first brought to light in the 2008 study, “Energy Performance of LEED for New Construction Buildings,” conducted by the White Salmon, Wash.-based New Buildings Institute. The study reviewed performance data of 121 buildings and plotted their actual energy use compared with their energy-modeling simulations. The good news was the majority of the buildings are performing near or above their simulations. The bad news was 21 percent of the buildings surveyed consumed more energy than the modeled code allowed. Very few of the buildings were performing right at the levels simulated in the energy models.
As a participant in the NBI study, I can say I’ve seen this disconnect. The building I submitted data for happened to be my office at the time--a LEED-NC Silver project. As part of the LEED submission, the building’s energy use was simulated and determined to be 35 percent less than the ASHRAE 90.1 standard. During the course of three years, the data we collected showed the actual energy savings was closer to 47 percent. We were lucky to be on the good side of being out of whack of the simulation. However, it still stresses the point that modeling is not matching up with real-world situations.
Every day it seems there are more programs available to simulate energy use in buildings. The problem is there isn’t enough validation for the programs that exist. Very little data can be found on the accuracy of the myriad of energy-simulation programs on the market. Operator error is another contributing factor. Someone who doesn’t understand all the design parameters or doesn’t understand the occupancy schedule of a building can create a simulation vastly different than real-world conditions.
With the new requirements by the USGBC in place, it is my hope that enough information about actual building performance can be collected to be valuable to the design community. After this information is collected, meaningful discussions about validation of energy-simulation software and accuracy of the simulations can be taken to the next level.
Nate Gillette is a licensed architect and the director of sustainability and energy consulting for PM Environmental Inc., Grand Rapids, Mich.