By Eric Simons
1. [Renzo Piano’s early sketch, full building photo]
To build the most ambitious green building imaginable, the California Academy of Science required its architects, engineers, and builders to be to become walking encyclopedias. A few of the things that came up: the heat load capacities of enclosed rainforest domes, the root development of wild strawberries, the engineering dynamics of helix-shaped cement walking paths, and the artificial light requirements of a coral reef. Kang Kiang, the local project architect, says he was pleased when the Academy chose to base the ground floor of the rainforest exhibit on the rainforest in his native Borneo -- in part because it was one less thing to learn on the job.
“We joked that we were all perfectly qualified to build the next combination planetarium-rainforest-natural-history-museum-aquarium that came along,” says Matt Rossie, an assistant project manager at Webcor Builders who worked on the Academy for two years.
The 410,000 square foot building started with a sketch of a few lines by world-renowned Italian architect Renzo Piano (above). His conception, which mirrored the hills of San Francisco, got him the job. Piano then invited collaboration -- from Kiang’s San Francisco-based firm Stantec, and Webcor among many, many others -- which helped the project leaders turn almost every fanciful sketch into steel-and-concrete reality.
Now complete after two years of construction, the complex will house a living coral reef, planetarium, natural history museum, rainforest dome, and research offices, all under a rolling living roof that looks as if the builders had lifted up a piece of San Francisco’s Golden Gate Park and stuck a museum underneath it. Although Piano is rightly hailed for his imagination, someone still had to turn that vision into steel and concrete and living strawberry plants. This is a story about how they did. In the end, Rossie says, “It comes down to a pipe fitter in the field looking up at the roof steel, saying, ‘How the hell am I going to do that?’”
2. [photo of roof, spotlights on plant trays and wildflowers]
“I need to talk about the roof,” Kiang says. “How do you pour concrete on a curving beamed roof?” Rossie, equally animated on the subject, leaps from his chair to sketch a diagram of the roof’s occasional 40-degree slope. “When you’re on a 40 degree slope and you pour concrete onto it, that’s a problem, because it’s subject to --” here he whips a marker and rapidly draws a bunch of downward arrows -- “gravity.” The solution: super quick-drying concrete sprayed through a high-pressure hose.
But while concrete hardens into place, dirt doesn’t. Kiang came up with the idea of putting in median strip boxes, called gabions, to help hold the soil in place. Then they needed a way to hole the gabions in place. A subcontractor suggested linking the gabions on both sides of the slope with nylon straps. “We originally referred to these as the underwire bra system,” Rossie says. Piano’s design called for growing native plant species like beach strawberries and prunella among wildflowers on the signature “living” roof. But the wildflowers grew so quickly that they blocked out the other native plants. So landscapers started the other plants a fully year early, in biodegradable coconut husk trays, so that by the time they were actually planted on the roof (still in their trays), they would have adequate root development. They used climbing gear to plant the roof.
3. [photo of piazza, and workers installing tresses]
For added degree of difficulty, the Academy asked that Piano’s piazza, a naturally lit open-air courtyard, be available year round. While supporting the glass above, the roof’s steel tresses, for seismic safety, needed to move around quite a bit—and to fit Piano’s graceful, curving design. Each tress had to be individually designed. If the tension wasn’t calculated correctly the glass would not, as Kiang delicately puts it, “stay.”
For a rain screen. Kiang and Piano designed a full-scale climate system that detects rain and automatically slides the screens up and over the ceiling. Then they created rollout acoustic shades to control the noise, and sun shades to moderate the heat on sunny days. The glass-and-steel tresses, rain screen, acoustic screen, and sun shades—all moving independently of each other—had to be hammered out between Kiang and Webcor in San Francisco, Piano in Italy, and glass experts in Germany. “It was,” Kiang says, “all about meetings.”
4. [photo of rainforest dome, with spiraling walking paths]
The four-story rainforest-in-a-dome is the first of its kind in the United States and the largest in the world. “We came up with the idea of spiraling ramps to connect the floors,” Kiang says, “But our challenge was, because they are not a constant radius, it’s difficult to figure out the slope.” The math was so complicated that almost no one could do it. Metal contractors complained it was all but impossible to build, and very expensive. That’s when Rossie’s background in theme parks came in handy. “I thought, ‘this was just a roller coaster,’” Rossie says. “Roller coasters do this all the time.” And he found a roller coaster builder in Utah whose estimate—to create shape-shifting circular ramps around a four-story living rainforest— saved a ton of money. The story is emblematic of the way the Academy, which expects to become the largest public LEED-certified building in the world, got built. “How do you plan for this? You don’t. It just kind of happens,” Rossie says.