California’s Hilly Green Roof

The California Academy of Science’s new $488 million building in San Francisco’s Golden Gate Park has an undulating 2.5-acre green roof. Biodegradable trays allow plant roots to weave a network of vegetation that stabilizes the plants on the sloping surfaces.

Italian architect Renzo Piano designed the California Academy of Science’s new $488 million building in San Francisco’s Golden Gate Park. The Academy gave its members an early glimpse of some of the new digs, but the official opening is set for September 27, 2008.

The Academy features what is being called the “greenest museum in the world,” a 2.5-acre “living roof,” or what is usually called a green roof. The green roof, said to be the largest in California, is the design of Rana Creek (an ecological consulting and design firm) in collaboration with the Renzo Piano Building Workshop and SWA Landscape Architecture. The green roof mimics San Francisco’s iconic Golden Gate Park landscape.

Speaking of green, and this is not a misprint, there are 1.7 million native plants on the green roof. Plant selection was a long and thoughtful deliberation by teams from

Rana Creek, the California Academy of Science’s botany group led by Frank Almeda, and SWA Landscape Architecture. The teams selected native plant species that would thrive on the roof without fertilizer or irrigation. Nine species—four perennials and five annual wildflowers, attract beneficial bees, birds and the endangered Bay Checkerspot and San Bruno elfin butterflies. The weight of the roof? Oh, about 2.6 million pounds.

The living roof is projected to absorb up to 3.6 million gallons of water each year, or about 98 percent of the storm water.

Its insulation factor will keep the interior building temperatures around 10 degrees cooler than would a standard roof, and the rooftop will be about 40 degrees cooler than its hardtop cousins.

San Francisco has some rather dramatic hills, so it seems appropriate that the roof has rolling hills, seven in number. Is Rome its sister city?

The steep slopes of the roof design will augment the roofs natural ventilation, drawing cool air into the central plaza and to the surrounding exhibit spaces. The slopes on the living roof’s rolling hills accommodate the Academy’s domed planetarium, rainforest and aquarium exhibits.

Rana Creek developed a green roof solution called BioTray that uses no toxic plastics or petrochemicals, plus prevents the plants from slipping off the rolling terrain. Modular 17-in. sq. by 3-in. deep biodegradable trays made of coconut husks and tree sap act as planters and roof tiles. The plant roots spread between the trays and weave a network of vegetation that is a very stable base for the plants, even on the sloping surfaces.

The new Academy is projected to consume 30 percent less energy than required by San Francisco codes. Sixty-thousand photovoltaic cells will provide 5-10 percent of the facility’s electrical requirements.
The project, as you might suspect, should attain LEED Platinum certification.

The New California Academy of Sciences houses the Kimball Natural History Museum, Steinhart Aquarium and Morrison Planetarium. The Academy conducts research in 11 fields of study, and is home to over 20 million scientific specimens. Visit www.calacademy.org.