Located in Golden Gate Park, the California Academy of Sciences is a LEED for New Construction Platinum-rated museum; it was certified by the U.S. Green Building Council, Washington, D.C. The museum includes a 2 1/2-acre (1-hectare) vegetated roof that goes to a depth of 6 to 7 inches (152 to 179 mm). The roof’s diverse assemblage of nine indigenous plant species, including the city’s most concentrated area of native wildflowers, is a new component in an ecological corridor for the city’s wildlife. The design architect, Renzo Piano Building Workshop, Genova, Italy, recreated the topography of San Francisco on the building’s roof with four undulating, steeply sloped domed structures that mimic the nearby Twin Peaks. To solve the technical challenges of planting on a steep slope, the green-roof consultant, Rana Creek Living Architecture, Carmel Valley, Calif., worked with the design team to develop a built-up vegetated roof system. A biodegradable, reinforced, modular propagation tray made from rapidly renewable coconut-coir fibers provides water retention for the plants and helps hold the growing medium in place during plant establishment.

The trays encourage plant growth from the use of a mycorrhizal biological inoculum that facilitates nutrient uptake and helps roots grow through the tray. About 27,500 square feet (2555 m2) of waterproofing material was used. The steep slopes act as natural ventilation and cooling. Fresh air, cooled by the vegetated surface, is funneled into the entry plaza where retractable skylights open to allow cool air to penetrate the building. The interior temperature is expected to be about 10 F (5.5 C) cooler than a building with a standard roof because of the thermal mass, surface moisture and insulation on the roof. The roof is anticipated to retain 2 million gallons (7.5 million L) of rainwater, preventing 70 percent of rainwater that falls on the roof to runoff. Any runoff is collected in basement-level cisterns and reused for roof irrigation. Stantec Architecture, San Francisco, served as the project architect, and SWA Group, San Francisco, served as the landscape architect. The implementation- landscape contractor was Jensen Corp., San Jose, Calif. Arup, San Francisco, served as the engineer. PROJECT SUBMITTED BY AMERICAN HYDROTECH INC., CHICAGO, WWW.HYDROTECHUSA.COM