Courtesy of Cass Calder Smith Cass Calder Smith designed this sustainable,1900-square-foot beach house in Stinson Beach, CA, as a second home for a three-generation San Francisco family. The design follows a rigorous sustainability program, achieving the Marin Planning Department's highest rating for resource efficiency. Photovoltaic panels generate all the home's electricity, sending surplus energy back to the grid. All the home's systems—hotwater, HVAC, and radiant heating—are integrated, electric-based, and powered by the PV panels on the roof. With the exception of the propane tank, t...