Ask a group of friends to name top sources of energy waste and pollution, and odds are good that no one would answer "my house" or "the place where I work." Yet the fact is that the nation's 5 million commercial facilities and 76 million residential buildings consume more than two-fifths of all our energy. They also account for just over one-third of the nation's carbon dioxide emissions (a chief culprit in climate change), about one-half of sulfur dioxide emissions, one-quarter of nitrous oxide emissions, and one-tenth of particulate emissions (all major contributors to smog and acid rain). The current construction boom is expected to add 38 million new buildings by the end of the decade, compounding the nation's air, waste, and water quality problems. Construction and demolition already generates 136 million tons of waste annually.