Energy Efficient Home Upgrades in Los Angeles For $0 Down -- Home Improvement Hub -- Via - The 1,800-sq. ft. story-and-a-half, three-bedroom cottage was built with passive solar, radiant-heating and an exterior wall system made of autoclaved aerated concrete (Hebel block). Simple footprint and truss roof brought down costs. Colored galvanized-steel roof has a 100-year life expectancy. James Cameron Build/Design, is in Pittsboro, North Carolina.