because the sample size was too small.) Of the 19 buildings (both medium- and high-energy-intensity use) with design and baseline model simulations, only one used less energy than had been predicted in the design case, and only four used less energy than the baseline simulation.
Six of the studies cited under energy use also studied water use. No studies were identified that focused only on water use in high-performance or green buildings.
Kats (2010) looked at 170 green buildings across the country. Of these, 119 reported projected reductions (from models) in indoor potable water use when compared to conventional buildings. The reductions ranged from 0 percent to more than 80 percent, with a median of 39 percent. Kats also found that water savings generally increased with LEED level of certification. Kats estimated the NPV benefits of water savings in typical green buildings ranged from $.50 per square foot to $2 per square foot, depending on building type and LEED level of certification.
Fowler and Rauch (2008) measured water use for 12 GSA green buildings. They established a baseline for domestic water use as the base load revealed from monthly water use data. Given these estimates, the average water use for the GSA green buildings was 3 percent less than the baseline.
Fowler et al. (2010) measured water use for 22 GSA green buildings and found that two-thirds of the buildings used less water than the GSA baseline, with the average being 11 percent lower. Of the 6 buildings with higher water use than the baseline, 5 had cooling towers or evaporative cooling, 2 had exterior fountains in a hot, dry climate, and 3 had non-typical operating schedules. For 5 of the 7 LEED-Silver buildings, water use was below the national and regional averages and the GSA baseline. Two LEED-Silver buildings (one with a cooling tower and one with evaporative cooling) had significantly higher water use than the average. Two of the 3 LEED-Gold buildings performed better than the baselines, but one used significantly more water than the baselines in both the 2008 and 2010 studies.
Menassa et al. (2012) found that 7 of 9 LEED-certified buildings used by NAVFAC reduced their water consumption by more than 15 percent when compared to NAVFAC non-LEED-certified similar buildings. Four of the LEED-certified buildings reduced their water use by 50 to 75 percent. Seven of 9 LEED-certified buildings reduced their water consumption between 18 and 72 percent. For the 4 LEED-Silver buildings for which water data were available, water use was 18 to 61 percent lower than their non-LEED counterparts. Two of the 3 LEED-Gold-certified buildings showed water savings of 56 and 60 percent, while the third used 90 percent more than its non-LEED counterpart.
Turner (2006) compared actual water use to modeled water use and to baseline code buildings in the Pacific Northwest. When compared to the baseline code buildings, 4 of the 7 buildings were using 8 percent less water. For the 7 buildings for which water use projections (models) were available, 6 buildings used at least slightly more water than projected.
Widener (2009) collected data on water use for 12 LEED-certified projects in Illinois. Widener found a wide range in annual water use and attributed it to individual project size, principal activity, and occupancy.
The committee identified three studies that attempted to compare operations and maintenance costs for high-performance or green buildings to other baselines.4
4 A study by Miller et al. (2010) looked at operations and maintenance costs for ENERGY STAR® buildings and was not reviewed by the committee because the Energy Star labeling program was not included as part of the statement of task.