Posted May 13, 2007, 8:48 AM
Join Date: Jun 2006
Location: San Francisco & Tucson
A GARDEN IN THE SKY
S.F. museum's roof puts green building techniques to the test
Carl T. Hall, Chronicle Science Writer
Saturday, May 12, 2007
Work crews are about to start planting the roof of the new California Academy of Sciences museum in Golden Gate Park -- an architectural capstone that also qualifies as one of the world's most ambitious biodiversity experiments.
Roof gardens are as ancient as Babylon and a deeply rooted fad in Europe, but the vegetated structure taking shape in the park is perhaps the grandest foray yet into what museum visionaries like to call "integrated regenerative architecture."
Gregory Farrington, the new executive director of the California Academy, views the roof as a unique scientific showplace designed to flip the conventional museum concept on its head. "Most museums have thick walls that separate the inside from the outside and put in the basement or on the roof all the systems that you need to make the place functional. Here, the idea will be to make the building itself into an exhibit, and there is no separation of the inside from the outside," he said.
Visitors to the $300 million science center who make their way up to a rooftop viewing platform after the museum opens next year will see none of the hulking ventilation towers and emergency generators that cap most big buildings. Those things and other utility systems have been buried underground to make way for 197,000 square feet of native strawberries, stonecrop and California poppies.
The pioneer plants are growing now in neat rows of portable "biotrays" -- 17-inch-square containers of biodegradable coconut husk woven in the Philippines -- at the Rana Creek Wholesale Nursery, specialists in West Coast native species, in Carmel Valley, 125 miles south of the construction site. Barring any last-minute construction delays, the biotrays will be trucked to the park starting May 23 and fitted into place one by one, like 3-inch-deep cake pans, on top of a complicated multilayered substrate that forms the roof's living skin.
In size and design, the academy roof is unprecedented, marked by seven domes and steep hillocks envisioned by celebrity lead architect Renzo Piano as a nod to San Francisco's undulating topography. The hills allow space inside for the museum's planetarium and the sky-lit dome of a rain forest display. But the idea is to draw attention outside to the rooftop forest of native plants, an estimated 1.7 million individuals representing four perennial and five wildflower species.
The plants will be the museum's first living residents, in effect expanding the greenswards of Golden Gate Park by 2 1/2 acres. But designers insist the project is more about philosophy than botany. The building's green crown is intended to push the idea of urban sustainability in the era of global warming. In that sense, the roof is a symbol of "the need for a general consciousness shift by our culture," said Paul Kephart, executive director at Rana Creek, who is serving as a project design consultant. "We are, in fact, responsible for climate change and impacts on biodiversity. Now we're taking action on those things," he said.
If such notions as a "green economy" and "living architecture" thrive as the visionaries hope, green roofs should be sprouting all over. In fact, that already is happening in the form of such other notable projects as the convention center in Vancouver, British Columbia, and the Gap headquarters in San Bruno.
California Academy patrons will still get to see the classic dioramas, fish tanks and live alligators that made the old natural history museum a popular destination in Golden Gate Park. The roof of the new structure adds a functional outdoor element, weaving the museum into ecosystems as well as tourist maps and guidebooks.
Engineers expect the roof to serve a working role for the building by attenuating sound and reducing storm water runoff. Its many skylights, and a retractable ceiling over a central piazza, will draw in sunlight and circulating air. It even will keep rain off people's heads. Equally important, the roof's plants were specially chosen to create habitat for the endangered bay checkerspot butterfly, draw bumblebees and hummingbirds, and maybe serve as a camping spot for migratory West Coast bird life.
Last week, Cooper Scollan, nursery manager at Rana Creek, stepped around a shrieking killdeer feigning a broken wing that had lain three eggs among the armeria and prunella at the nursery, soon to be relocated to Golden Gate Park. A work crew methodically moved along the rows of biotrays, removing weeds and planting new seedlings. Scollan and colleagues collected many of the starting plants and seed stock from private landowners around the Bay Area. The nine plant types, including annual wildflowers not yet seeded, emerged from field testing of about 30 species as the most likely to endure on the roof with minimal or no watering after an initial break-in period.
At Golden Gate Park, meanwhile, academy botany chief Frank Almeda took visitors for one of the final looks around the still-naked rooftop last week. A thick sandwich is now being built up to welcome the plants, including layers for insulation, waterproofing and drainage, plus 3 inches of soil mix beneath the coconut husk.
It's costing about $17 a square foot. No one can predict how all the plants will fare, and there's a chance many problems will crop up, including the possibility of a quick takeover by the fast-spreading beach strawberries.
Almeda said he was confident the roof will be healthy and plenty green by the time the museum completes its elaborate move-in and officially opens, scheduled for October 2008, even if the current dry spell deepens into drought. "Native plants," he said, "are built to adapt."
More information can be found on the Academy's Web site at: links.sfgate.com/ZDV
California Academy of Sciences
Museum location: Golden Gate Park
Architect: Renzo Piano
General contractor: Webcor Builders
Roof consultant: Rana Creek Living Architecture
Expected completion: November 2007
Museum opening: Fall 2008
Temporary museum site: 875 Howard St. near downtown San Francisco
Total project cost: $429 million, including construction, temporary downtown facility and moving costs
E-mail Carl T. Hall at email@example.com.
This article appeared on page A - 1 of the San Francisco Chr