THE RAIN FOREST
The 90-foot-diameter dome for the
Rainforests of the World exhibit
(top) is self-supported and made of
steel piping. On top of it, the living
roof’s slopes (above) were created by
curved and faceted steel beams.
The four corner buildings are independent structures, with the contoured concrete roof (below)
joining them together.
Bottom right model, courtesy
Renzo Piano Building Workshop;
other images courtesy Arup
Sitting in a darkened conference room at
Arup’s San Francisco office on Market Street,
Peter Lassetter flips through a book of early engineering sketches for the California Academy of
Sciences. Lassetter, a principal at the firm and
the project director for engineering services of the
building, pauses on a drawing from 2001, when
the design was still very much in flux. Across the
rough sketch is written an annotation in clear
printed letters: “Crazy! Don’t do it!” That engineer’s plea may well have been heeded—Lassetter
couldn’t quite make out from the drawing what
was being warned against—but Arup certainly
toyed with its share of crazy ideas while working
on the Academy, which demanded a team of 320
people (drawn from its London, San Francisco, Sydney, and Hong Kong offices, among others) and
included the structural, mechanical, and facade
engineering; sustainability consulting; and lighting design. Many of those ideas, in fact, ended up
forming the sustainable backbone of the Academy,
the features that transformed it from a very green
museum into a living, breathing one.
The breath of the museum is both literal and
metaphorical: its lungs can be found in the contoured two-and-a-half-acre green roof (the Academy calls it a “living roof”) that is not only the
building’s signature gesture, but also the key to its
energy-efficient design. The two largest hills rise
27 feet above the roof line as they follow the outlines of the spherical planetarium and artificial
rain forest below; the other five slopes weren’t designed with a programmatic purpose in mind. (
According to the museum’s press department, they
are meant to evoke San Francisco’s quasi-mythical
seven hills. As an alternate explanation, Lassetter
deadpans, “There’s no truth to the fact that Renzo’s
from Italy and there are seven hills in Rome.”)
But Alistair Guthrie, a director of Arup and a
mechanical engineer, devised a way to use the
hilly topography to turn the roof into what Jean
Rogers, a sustainability consultant at Arup, calls
an “organ regulating the building’s metabolic processes.” A gap of four feet was left between the
tops of the two spheres and the roof, creating what’s
known as a stack effect: the narrowing space acts
as a chimney, rapidly drawing out warm air through
a series of skylights. At the same time, cool air
enters the space through ground-level vents and
doors, and a westerly breeze across the roof sucks
Below: An early model of the Academy.
The planetarium and artificial rain forest
are on the east-west axis while the entry
corridor runs north-south.
