|Species Selection || |
Plant species were tested to ensure that they would survive on the rolling hills of the roof with minimal artificial irrigation and fertilization. They were also selected to provide habitat for native wildlife. Out of nine original species planted on the roof (beach strawberry, self heal, sea pink, stonecrop, tidy tips, miniature lupine, California plantain, California poppies, California goldfield), two species have emerged as dominant:
- Beach strawberries (Fragaria chiloensis) produce berries that attract a number of native birds.
- Self heal (Prunella vulgaris) bears large tubular flowers that are attractive to hummingbirds and bumblebees.
In addition, since 2008, dozens of other native species have been planted to promote biodiversity. These include the common yarrow (Achillea millefolium), beach sagebrush (Artemisia pycnocephala), sea lettuce (Dudleya cespitosa), powdery dudleya (Dudleya farinosa), seaside daisy (Erigeron glaucus), coast buckwheat (Eriognoum latifolium), red buckwheat (Eriogonum grande var. rubscens), and California fuchsia (Epilobium canum). In total, approximately 75 native species inhabit the living roof.
|Coconut Husk Trays || |
During the initial installation, 1.7 million individual plants were planted into over 50,000 biodegradable coconut husk trays. These trays, which were composed of sustainable waste products from coconut plants in the Philippines, allowed for easy roof installation and provided immediate root protection. They also supported indigenous cooperative enterprises.
|Roof Components || |
The living roof is composed of seven layers of material, designed to create insulation, prevent runoff, retain soil, allow for drainage, and promote healthy plant growth. From top to bottom, these layers are:
- Biodegradable coconut husk trays containing three inches of soil and nine species of native California plants
- An additional three inches of soil
- An erosion control blanket designed to retain soil on the roof’s slopes, retain moisture mid-slope, and control pest plants
- A drainage layer to prevent to plants from rotting
- An insulation layer to stabilize internal building temperatures
- A waterproofing layer
- A concrete slab that follows the contours of the roof’s seven hills
Additionally, a grid of rock gabions helps hold soil in place and create access routes for roof maintenance. Operable skylights serve as vents and allow natural light to reach the living coral reef and rainforest below.
|Roof Stats || |
- The living roof decreases the urban heat island effect, staying an average of 40 degrees cooler than a standard roof
- It can absorb up to 3.6 million gallons of water per year (about 98% of all storm water), preventing runoff from carrying pollutants into the ecosystem
- It provides excellent insulation, keeping interior temperatures about 10 degrees cooler than a standard roof and reducing low frequency noise by 40 decibels
- Total square footage: 197,000 square feet (4.5 acres total roof space including solar panel canopy; 2.5 acres of planted material)
- Total weight of soil and plants: 2.6 million pounds
- Total cost: $17.00 per square foot
| Active Research and Education || |
In addition to interpretive signage and regularly scheduled tours and programs, the Academy has developed a number of projects to capitalize on the roof's potential for research and education:
- The Academy conducts a citizen scientist program in which visitors help collect data for a long-term roof monitoring project. For example, citizen scientists identified 39 arthropod families and 38 bird species on the roof from June 2009 - Feb. 2011.
- High school and college interns from the Academy’s Careers in Science program are monitoring an empty plot on the roof's west side to determine which plant species arrive and colonize on their own.
- Students from San Francisco State University (SFSU) took monthly samples of the roof's insect fauna and created a DNA sequence database to track changes in biodiversity over time.
- From 2008-2009, a graduate student from SFSU monitored arthropod biodiversity on the roof and the ground for a master's thesis project.
|Project Team || |
Architecture: Renzo Piano Building Workshop (Genoa, Italy); Stantec Architecture (formerly Chong Partners Architecture) (San Francisco, CA). Engineering and Sustainability Consulting: Arup. Living Roof: Rana Creek Living Architecture. Installation: Jensen Corporation. Landscape Architecture: SWA Group. General Contractor: Webcor Builders.
|Media Contacts || |