With a sleek prototype in Emeryville, California, under its belt, Simpatico Homes sets out to redefine prefab's cost—and footprint.Simpatico’s factory-built pieces come in two ceiling heights: nine or ten feet. Just above the ceiling, the customization continues—Simpatico modules can be designed to house green roofs, which boost insulation, absorb rainwater, and reduce runoff. In fact, the prototype makes use of all the rooftop spaces: Each one contains either a green roof, the 6.2-kilowatt solar-panel array, a roof deck, or terraces. “Every inch of the roof is doing double-duty,” Krubiner says. Read more about the prefab house here. Photo by: Jake Stangel