Reducing your impact on the earth is not just a question of what you drive but also of what you live in. Residential energy use accounts for 16% of greenhouse-gas emissions. If you begin thinking green at the blueprint stage, however, low-tech, pragmatic techniques will maximize your new home's efficiency. Installing those systems from the ground up is cheaper than retrofitting. "Doing simple things could drastically reduce your energy costs, by 40%," says Oru Bose, a sustainable-design architect in Santa Fe, N.M. For example, control heat, air and moisture leakage by sealing windows and doors. Insulate the garage, attic and basement with natural, nontoxic materials like reclaimed blue jeans. Protect windows from sunrays with large overhangs and double-pane glass. Emphasize natural cross ventilation. "You don't need to have 24th century solutions to solve 18th century problems," Bose says. Next, consider renewable energy sources like solar electric systems, compact wind turbines and geothermal heat pumps to help power your home. When you're ready to get creative, GreenHomeGuide.com will help you find bamboo flooring, cork tiles, and countertops made from recycled wastepaper.