California Academy of Sciences Green Roof

• Attract native pollinators and support long-term biodiversity research.
• Capture at least 90% of on-site stormwater.
• Increase thermal comfort for museum visitors and wildlife during hot summer days.
• Accommodate a wide variety of educational programming including guided tours and self-led learning.
• Reduce energy demand for heating and cooling within the museum’s climate-controlled exhibits.
• Offset operational energy costs with on-site renewable energy systems.

• A modular plant installation system comprising 50,000 biodegradable 17-inch square containers made from tree sap and coconut fibers blankets the roof, holding a total of 1.7 million individual plants.
• A 7.3-meter (24-ft) gabion grid creates a structural drainage system that helps stabilize soil on the green roof’s steep slopes while doubling as footpaths for maintenance crews. Additional stormwater is sent to a storage tank on the ground floor of the museum.
• 6 inches of engineered soil (composed of 40% organic material) provides a substrate for plant roots to grow into as they mature while helping to insulate the building below, reducing the museum’s overall energy use.  
• A rich diversity of native California plant species such as beach strawberry (Fragaria chiloensis), common selfheal (Prunella vulgaris), broadleaf stonecrop (Sedum spathiulitholium), coastal tidytips (Layia platyglossa), miniature lupine (Lupinus bicolor), and California poppy (Escscholzia Californica), attract pollinators and ‘pirate bugs’ that feed on less desirable insects.
• Weather stations on the green roof monitor wind, rain, and temperature. These weather stations help inform the building’s mechanical amenities, including the opening and closing of skylights, regulation of temperature for the interior 4-story rainforest biome, and regulation of the climate of the interior piazza.
• An ADA-accessible 3,500-sf observation deck supports outdoor educational programming for students, researchers, and the general public.

• The primary gabion grid worked well for stabilizing soil and vegetation on the living roof’s steep (up to 60-degree) slopes and helped support the initial plant installation process. However, over time, the gabion system made it more difficult to replace plant material as a part of long-term maintenance because plant root systems grew into the gabion core.
• The California native plants that were selected for the living roof were chosen, in part, for their limited irrigation requirements during San Francisco’s dry season, and one of the ambitions for the project was to minimize irrigation once the plants had been established. However, when these plants began to go dormant (as planned), the museum received complaints and criticism from key supporters and the general public. As a result, the museum decided to irrigate the rooftop plants year-round. This decision resulted in a more water- and energy-intensive outcome than had originally been championed.
• While undulating hills make up the most visible sections of the living roof, there are several areas that are flat. This has allowed excess water to puddle in some areas, creating the potential for damage to the drainage board and waterproof membrane below the soil.
• The carbon capture from the green roof is minimal. The plants that currently populate the roof are mostly grasses and herbaceous perennials that do not capture as much carbon as trees and woody shrubs. While the designed 6-in soil volume may not have been suitable for planting larger species, there may have been opportunities for increasing soil volume to accommodate more carbon sequestration in some areas.
• The museum receives 1 million visitors annually, and half of them visit the living roof. The green roof observation platform is only accessible via one elevator and the publicly accessible area is small relative to the rest of the roof.  A second entrance and an expanded deck footprint may have helped support expanded access and additional opportunities for facilitating research.

17”x17” biodegradable modular planters: Originally marketed as BioTray™ (developed by Rana Creek). Later, commercial rights to the product were purchased by Tremco

Project Team

Landscape Architect: SWA Group
Architect: Renzo Piano Building Workshop
Executive Architect: Stantec Architecture; Chong + Partners
Engineering and Sustainability: Ove Arup & Partners
Civil Engineering: Rutherford & Chekene
Horticultural Consultant: Rana Creek Habitat Restoration
Irrigation: Dickson Associates
General Contractor: Webcor Builders

Role of the Landscape Architect

The role of the landscape architect was to bridge the technical requirements and the aesthetic design vision for the living roof. The scope of work ranged from design through construction observation on the 2.5-acre living roof and all exterior grounds, including an on-structure park above an entirely new parking garage (outside the scope of this case study). The landscape architect worked closely with architects, engineering/sustainability consultants, and ecology/horticultural consultants to solve complex problems, from the development of a native plant palette to the system for delivering the planted trays to the site.