This project is a second floor addition onto a house for a couple and their two children in Noe Valley. The goals were pretty simple: They wanted to expand the house to allow the family to stay in their present location, and do it in a way that would reduce their carbon footprint while remaining practical and financially feasible. Due to the fact they have two children, a boy and a girl who were close to coming of age, they were very cognizant of the need to have separate bedrooms for each of them. With site constrictions including large mature trees, an upper level was added including a striking butterfly roof, which is integral to rainwater storage. The home boasts San Francisco’s first approved rainwater storage system, utilizing the water for landscaping, toilets and laundry, reducing non-potable water usage by approximately 50 percent.