The sleek prefab i-house by Clayton Homes, available nationwide, won’t hurt your pocketbook and comes packed with an abundance of green goodies, including low-VOC building materials, low-flow fixtures, dual-flush toilets, a metal roof that allows rainwater harvesting, high-efficiency insulation and EnergyStar appliances. Optional features include solar panels and a tankless water heater. Retail price depends on the options chosen, but starts at $78,000 (final cost after construction ranges from $120,000 to $160,000). Energy Saver Plus models sport programmable thermostats, low-e windows, and compact fluorescent lighting. If that’s not incentive enough, consider this vote of confidence: Berkshire Hathaway, the firm owned by investment wizard Warren Buffett, bought Clayton Homes in 2003.