The U.S. Green Building Council's Leadership in Energy and Environmental Design (LEED) Green Building Rating System provides many paths to certification, some of which result in a more energy-efficient building than others. Thus, just because a building is LEED-certified does not mean significant opportunities for energy savings cannot be found. As the case studies at the end of this article show, savings usually can be had for little or no capital investment by fine-tuning the operations of a building.

ENERGY PERFORMANCE OF LEED-CERTIFIED BUILDINGS

In perhaps the most comprehensive study of the measured energy performance of LEED-certified buildings to date,¹ the New Buildings Institute (NBI) found that average energy use in LEED for New Construction and Major Renovations- (LEED-NC-) certified buildings is 25- to 30-percent better than the national average. However, the buildings studied displayed a large degree of scatter, with one-quarter having Energy Star ratings below 50, “meaning they used more energy than average for comparable existing-building stock.”

“How can this be?” you may ask. Are there not energy prerequisites that must be met for LEED certification to be achieved? The answer is, “Yes, but ….”

Of the nine LEED rating systems — LEED-NC, LEED for Existing Buildings: Operations & Maintenance (LEED-EB), LEED for Commercial Interiors (LEED-CI), LEED for Core & Shell (LEED-CS), LEED for Schools, LEED for Retail, LEED for Healthcare, LEED for Homes, and LEED for Neighborhood Development — LEED-EB is the only one requiring an actual demonstration of whole-building energy performance, and it accounts for only 8.9 percent of LEED-certified buildings (Figure 1).

FIGURE 1. Breakdown of 2,666 LEED-certified buildings, June 2009.

Because, of course, the buildings do not yet exist, LEED-NC relies entirely on simulation-model results. According to the NBI study: “Energy modeling turns out to be a good predictor of average building energy performance for the sample. However, there is wide scatter among the individual results that make up the average savings. Some buildings do much better than anticipated; on the other hand, nearly an equal number are doing worse — sometimes much worse” (Figure 2). When individual-building models that inherently have a high degree of variability are used to predict energy use, and LEED points are awarded based on those models, it is not surprising that buildings in which actual energy performance falls short of expectations “slip through the cracks” and become certified.

FIGURE 2. Wide scatter in measured vs. design energy use.

Only about half of the LEED-NC buildings in the NBI study demonstrated actual energy performance that would qualify for recertification under LEED-EB.

CASE STUDIES

It stands to reason that in a building in which modeled energy performance is much higher than actual energy performance, there will be ample opportunity to reduce energy use. But what about buildings that already are performing well? Are there still savings opportunities to be found? Following are two examples of buildings far exceeding the minimum energy-performance requirement for LEED certification in which significant energy-saving opportunities were found through simple, low-cost energy audits. The common characteristic is an owner motivated to continue to reduce costs and improve energy performance.