Nearly half the energy consumed in the United States each year and half of America's greenhouse gas emissions.

This solar-powered home in Salado, Texas, is enormous at 21,000 square feet, but its environmental footprint is small. Architect Stephen Gist, pictured here in January 2006, positioned the building so that the sun warms the concrete floor in the winter and shade protects it from the back in the summer. By some estimates, buildings account for nearly half the energy consumed in the United States each year and half of America's greenhouse gas emissions.