The GSA report was conducted under a contract with the U.S. Energy Department's Pacific Northwest National Laboratory (PNNL). In a report submitted by the laboratory to GSA, "Sustainable Building Rating System Summary," PNNL researchers compared the following five methods for rating whether a building design and construction is green: Building Research Establishment's Environmental Assessment Method (BREEAM); Comprehensive Assessment System for Building Environmental Efficiency (CASBEE); GBTool; Green Globes US; and LEED.
Although each of the rating systems has merits, "Based on the results [of the report], GSA finds that the LEED rating system continues to be the most appropriate and credible sustainable building rating system available for evaluation of GSA projects."
GSA cited multiple reasons for its conclusions about the LEED system. First, LEED applies to all GSA project types, including new and existing buildings, interiors, and other areas covered by USGBC standards. Second, it "tracks the quantifiable aspects of sustainable design and building performance," a major focus of federal programs under the impetus of the Government Performance and Results Act and a general demand for performance measurement. Third, trained professionals verify LEED. Fourth, it has a "well-defined system for incorporating updates," which LEED is now undergoing through a far-reaching LEED 3.0 update. According to the report, LEED is also "the most widely used rating system in the U.S. market."