This book assesses, for the first time, what the Federal government is doing, in policy and practice, to make its buildings more environmentally sustainable, and provides recommendations for how the Federal sector can make even greater progress. Why is this important? Green or sustainable building is the practice of designing, constructing, operating, maintaining, and removing buildings in ways that conserve natural resources and reduce pollution. Green building is expanding around the world, and the Federal government is leading by example. This approach is important for the Federal government (and has become one of our office's priorities) for three reasons. First, buildings affect land use, energy use, communities, and the indoor and outdoor environment. Given the size and scope of Federal buildings - the government owns nearly 500,000 buildings covering 3.1 billion square feet, accounting for 0.4 percent of the nation's energy usage, and emitting about 2 percent of all U.S. building-related greenhouse gases - we have the opportunity and responsibility to reduce these impacts. Using sustainable principles in buildings can reduce these impacts and also improve worker conditions and productivity, increase energy, water, and material efficiency, and reduce costs and risks. Second, sustainable buildings can be showcases to educate people about environmental issues, possible solutions, partnerships, creativity, and opportunities for reducing environmental impacts in our everyday lives. Hundreds of millions of people visit and work in Federal facilities each year. And third, green buildings represent the application in one place of many of the sustainable concepts the Federal government is working on - such as environmental management systems, waste prevention and recycling, and green product purchases. We prepared this book because there is no other single source of information about what all the Federal government is doing to "green" its building stock, and, by doing so, we hope to spark discussion and create opportunities for greater Federal stewardship.