CHICAGO, IL — The Chicago chapter of the U.S. Green Building Council this week released the first study of post-construction performance of LEED-certified buildings in the region, measuring their performance compared to conventional buildings.
The group's report, Regional Green Building Case Study Project: a Post-Occupancy Study of LEED Projects in Illinois," summarizes the first year of a mulit-year study of 25 LEED-certified projects in the Chicago area, looking specifically at energy intensity, greenhouse gas emissions, water use, operating costs and occupant comfort.
The report found a wide variance in resource use at the buildings, all of which were certified under an older version of the LEED standard. Figure 1 below shows the Energy Usage Intensity (EUI) for 17 of the 25 projects, each of which provided full energy data for the facility. The energy used in BTUs per square foot per year varies from 30,000 to nearly 140,000 in these projects, but on average performed 24 percent better than the national average.
Those same 17 projects generated 25.8 pounds of CO2-equivalent greenhouse gases per square foot per year, according to the report. Water use for all 25 facilities was measured at 5.9 gallons per occupant per day.
The next phase of the project will add an additional 25 LEED-certified projects to the study, and will further the energy use survey, providing results back to the building owners as a way of boosting the efficiency of the facilities.
"With an understanding of operational issues, tenant behavior, and maintenance practices, building owners and managers can implement ongoing changes that lead to increased building performance and sustainability over time," said Doug Widener, Executive Director of the U.S. Green Building Council's Chicago Chapter.
Other findings in the first round of the study include very high levels of occupant comfort: Overall satisfaction with the buildings, as shown in Figure 2 below, were consistently high across almost every category measured.
Also among the findings from the report are that a premium for green buildings practices exists: The average premium reported by the facility owners was 3.8 percent, in line with the national average. Those premiums can be offset by savings in energy and water use, as well as overall quality of workplace environment.
The full report from the USGBC's Chicago chapter is available for download from GreenerBuildings.com.
Image CC licensed by Flickr user theycallmetelly.