GAO was asked to review federal green building efforts and agencies' use of third-party certification systems. This report examines (1) federal efforts to support agencies' implementation of key green building requirements, (2) select agencies' use of third-party certification systems, and (3) challenges select agencies face in implementing requirements. This is a link to highlights from GAO-15-667, a report to the Ranking Member, Committee on Homeland Security and Governmental Affairs, U.S. Senate.