Photos: San Francisco's greenest home?

Robin Wilson, the owner and general contractor, completed the "Idea House" project with architect John Lum and Sunset Magazine in 2007. They added a level to an existing two-story building. The result is a three-level 3,500-square-foot home with a separate 1,200-square-foot unit.

The urban infill project is a five-minute walk to a subway station and close to many small, neighborhood stores. However, affordable-housing activists have criticized the large building for being located in a low-income neighborhood.

Outside, an ECO Paver permeable sidewalk allows rainwater to seep into the ground instead of flowing into sewer systems. The two-car garage includes a natural gas pump.