Pictured are two homes in Philadelphia’s East Kensington neighborhood: a larger one on the corner (120K House) and a smaller home to the left (100K House). Built by green developer Postgreen, these two-story LEED Platinum loft townhomes were named for their building costs (labor and materials). Postgreen decided to hang onto the smaller home, which at 1,150 square feet was built for about $100,000 or, more accurately, $100 per square foot. The larger, 1,270-square-foot home cost around $120,000 to construct and sold for $265,000. Both units sport solar hot water systems, rainwater collection, low-flow fixtures, dual-flush toilets, CFL lights, low- and no-VOC finishes, and “green wall” ivy landscaping. Postgreen has since built five more and has 30 more in the works — all in the Philadelphia area.