Extensive Institutional

Project: California Academy of Sciences
Award Recipient: Rana Creek Living Architecture
Client: California Academy of Sciences
Design Architect: Renzo Piano Building Workshop
Project Architect: Stantec Architecture (formerly Chong Partners Architecture)
Landscape Architect: SWA Group
Engineer: Arup
Implementation-Building Team: Webcor Builders
Implementation-Landscape Contractors: Jensen Corporation Landscape Contractors
Materials Supplier: American Hydrotech, Inc.

In the heart of San Francisco’s beloved Golden Gate Park, the California Academy of Sciences’ new LEED® Platinum-rated museum now hosts the largest green roof of any natural history museum in the world. The roof top’s 2.5 acres of planted material gives the Academy one of its most forward-thinking exhibits, a dedication to research and education in both urban ecology and living architecture. Visitors will be awed by the increased vegetation and unique architecture. At the same time, the roof’s diverse assemblage of nine indigenous plant species is a new link in an ecological corridor for the City’s wildlife. Habitat space taken away from urban development will be restored for the native plants and animals of the area. For San Francisco, the green roof creates the most concentrated area of native wildflowers within the city.

One of the ingenious designs of Renzo Piano was his vision of continuing the topography of San Francisco through the Academy’s rooftop. Mimicking the hills of nearby Twin Peaks, the roof has four undulating, steeply sloped domed structures. This however presented design challenges for the installation of the plants. In order to solve the technical challenges, Rana Creek worked with the design team to develop a built-up green roof system with stacked benefits. The key to this process was the BioTray®, a biodegradable, reinforced, modular propagation tray made from rapidly renewable coconut coir fibers. This tray provided water retention for the plants and helped to hold the growing medium in place during plant establishment. Contract-grown by Rana Creek’s Wholesale Nursery, the BioTrays® encourage plant growth from the use of a mycorrhizal biological inoculum that facilitates nutrient uptake and helps roots to grow through the tray providing further stabilization.

The steep slopes of the roof act as a natural ventilation and cooling system. Fresh air, cooled by the vegetated surface, is funneled into the entry plaza, whose retractable skylights peel back to allow cool air to sink into the building to offset mechanical cooling demand with natural ventilation. Additionally, the thermal mass, surface moisture and insulation in the roof assembly are expected to maintain the building's interior an average of 10 degrees cooler than a standard roof would. These energy savings are being empirically investigated and the results have been presented at the 2008 Greening Rooftops for Sustainable Communities Conference.

The roof also retains 2 million gallons of rainwater, preventing 70% of the rainwater that falls on the roof from becoming runoff. The water that does run off the roof is collected in basement-level cisterns and reused for roof irrigation. No potable water will be used to irrigate the living roof.

The roof covers an ambitious 197,000 sq. ft. to a depth of 6-7 inches and cost $17 per sq. ft. In conjunction with the building’s other innovative sustainable features, the living roof contributes to many of the anticipated LEED® points, which, when achieved, will make the Academy the world’s largest LEED® Platinum -certified public space. Ambitious, innovative, informative and visually spectacular, the green roof on the California Academy of Sciences exemplifies all the potential of the extensive institutional green roof.

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