Can a 12,000-square-foot house really be eco-friendly? What about Bill Gates’s 40,000-square-foot house built of salvaged wood? Architect Will Bruder says adding green features like geothermal heating and solar panels to mongo homes with five-car garages is merely a way “to rationalize decadent expenditures.” Daniel Chiras, an enviro professor, says, “[I]f it’s a 5,000-square-foot-house, it has to be furnished, heated, cooled, and maintained. That takes a lot of resources and energy. They’re fooling themselves if they think it’s okay.” Others are all for thinking big. Architect William McDonough says, “Size doesn’t have to matter.” David Warner of Redhorse Constructors in San Rafael, Calif., agrees: “If a guy with a home over 10,000 square feet who doesn’t think of himself as green still decides to use photovoltaic power sources, I consider that a victory.”