If you have a grove of redwood trees, you'll get cool air sinking out of the trees and down to the ground," Parker says. "We designed the house to take advantage of that natural convection to cool it in the summertime." Passive solar design provides warmth. "It doesn't look like a typical passive solar house with big south-facing windows designed to soak up sun and heat," he says. "We studied the length of every overhang to see how much sun and heat you're going to get from them at every time of year and day." The house also has a radiant hydronic heating system to provide additional warmth.