Living roof tops the new Academy

September 12, 2008 12:00:00 AM PDT
From the start, the new California Academy of Sciences has been a giant experiment, including the roof.

The entire building is covered with a living roof - a huge expanse of dirt with plants growing, almost as nature intended. The original idea came from ground breaking architect Renzo Piano.

"He spent some time walking around Golden Gate Park, getting a sense of the surrounding topography in SF and he came back after spending about an hour up on the roof of the old building, and he had this every iconic now line drawing," Academy communications director Stephanie Stone said. "It was a green felt tip pen sketch of a rolling roof line."

That sketch launched plans for what may be the most complicated living roof ever built. Curved steel beams were installed to create a rolling hillside effect like the hills of San Francisco.

"We had to come up, using specific types of models, ways to be able to look at the steel, then throw it through bending machines to get just the right proportions," Jes Pedersen of Webor Builders said.

The roof is made of seven different layers, providing everything from insulation to drainage. It is designed to absorb 98 percent of the rain water that hits it.

"That's important because normally when rain water hits a roof, it acts as a conduit, carrying pollutants from that roof and the street out into the ocean or out into the bay, but we're capturing the rain water, and the plants are using it and you are reducing that run off," Stone said.

Each section of the roof was tested to ensure that it was waterproof. While that was happening, more than 100 miles away, the plants for the living roof were starting life in Carmel Valley.

There are nine types of plants on the roof, all native to Golden Gate Park. Each variety was chosen to provide habitat for birds and insects.

"The roof may last up to 400 years," Rana Creek Ecological Designer Paul Kephart said. "These are long lived plants. Resistance and resilience, that's what we are building into the structure and building in to the natural landscape."

The plants were grown in biodegradable trays made of coconut husks. In May 2007, crews finally began placing the trays on the roof. The plants will be watered for a few months; after that, they are supposed to be self-sustaining and enjoyed for generations.

"Hopefully our kids can say, 'oh my Daddy did that, he was up there working on the top of that roof,'" landscape foreman Daniel Romero said.

Since the roof was finished, insects have already discovered the flowers and the plants are growing in as expected. Beyond beauty, there is another benefit.

" All that soil - there's six inches of soil up on the roof, makes it a great insulator, so we'll use a lot less energy on heating and cooling the building beneath it," Stone said.

Written and produced by Jennifer Olney


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