Reducing environmental impact

Green building practices aim to reduce the environmental impact of buildings, so the very first rule is: the greenest building is the building that doesn't get built. New construction almost always degrades a building site, so not building is preferable to green building. The second rule is: every building should be as small as possible. The third rule is: do not contribute to sprawl (the tendency for cities to spread out in a disordered fashion). No matter how much grass you put on your roof, no matter how many energy-efficient windows you use, if you contribute to sprawl, you've just defeated your purpose. Urban infill sites are preferable to suburban "greenfield" sites.

Buildings account for a large amount of land. According to the National Resources Inventory, approximately 107 million acres (430,000 km²) of land in the United States are developed. TheInternational Energy Agency released a publication that estimated that existing buildings are responsible for more than 40% of the world’s total primary energy consumption and for 24% of global carbon dioxide emissions.^[6]