Vancouver’s VanDusen Botanical Garden is considered young compared to its counterparts in other cities—from 1911 to 1960, the 55-acre property was home to a golf club. The site was then considered for commercial development until the neighbors objected and the VanDusen Botanical Garden Association helped save the property for use as a botanic garden. The gardens opened in 1975; in 2011, Peter Busby, Intl. Assoc. AIA, and his colleagues at Perkins+Will reinvigorated the property with a new $14.4 million (CAD) visitor center.
Located on the southeastern corner of the property, the 19,000-square-foot building was designed to target the VanDusen leadership’s interest in attaining both LEED Platinum certification and meeting the Living Building Challenge (LBC). One reason for the sustainable goals is that the mission of a botanic garden is conservation, explains garden director Harry Jongerden. As such, “the philosophy of the building and a botanic garden is the same,” he says.
To realize this vision, Busby designed an organically shaped, dramatic single-story structure that introduces visitors to the naturalistically planted grounds. Curving rammed-earth walls beneath an undulating roof lead visitors from multiple entries through to a central, circular atrium. From this single point under a contemporary oculus, one can step out into the garden or access the building’s amenities, which include a store, food services, and educational and rental spaces.
The building’s design draws on natural forms with nary a right angle in sight. The typical roof panel is 15 feet by 65 feet and curves along all three axes—with more than 50 different panels needed to enclose the building. They were first drawn by Perkins+Will using Rhino, then transferred to Revit for working drawings and fabrication. The panels were prefabricated, incorporating everything—structure, sheathing, roofing membrane, as well as rough-ins for fire protection and electrical services. “It’s tricky to bend sprinkler lines,” says Ledcor Construction project manager Rebecca McDiarmid. “We used BIM to sort out the conflicts. There would have been a number of spectacular ‘oops’ if we hadn’t.” The undulating roof required a steel connection detail that would accommodate the many different angles with which the roof panels meet the structural members. “We developed a standard that works with any curve,” Busby says. Construction of the relatively small, single-story building required the use of Vancouver’s largest crane in order to place the roof panels without disturbing the towering trees that surround the building.
The LBC is just that—a challenge. McDiarmid recalls how the hundreds of linear feet of drain tile required for the building had to be produced by hand drilling thousands of holes in high-density polyethylene pipe—a substitute for the LBC-banned PVC. “That’s the kind of thing LBC does to you,” Busby says. “It can drive you crazy.” Other materials were difficult as well. “Subcontractors would pull their LEED files on materials,” McDiarmid says, “but that’s not enough.” It was teamwork that made it happen. “The subs really got on board,” Perkins+Will associate principal Jim Huffman says. “The Living Building Challenge is less flexible than LEED. It’s all or nothing.” Silicone was substituted for neoprene in several assemblies to meet challenge requirements, knowledge that was transferred between subcontractors on the project.
VanDusen achieves net-zero energy through a variety of techniques including solar hot water, photovoltaic panels, and geothermal boreholes. Its net-zero water system makes it the first building in more than 45 years in Vancouver to treat blackwater on site, though the city required both water and sewer systems to be connected to the city service. A similar strategy is used at the Perkins+Will-designed Centre for Interactive Research on Sustainability at the University of British Columbia but that building is in a different jurisdiction.
At the north end of the building, mostly hidden from view, is the portion of the building that houses the mechanical room. Here, the roof comes down to grade, serving several useful purposes. It hides the blackwater piping that exits the building to a percolation field. “And it allows critters to get onto the green roof,” Busby says. “It promotes biodiversity. It’s about man and nature coming together.” That’s a theme that remains central to the mission of both the garden and Busby’s work.
At the center of the VanDusen Botanical Garden Visitor Centre’s multipetaled structure is a circular space topped by a daylit oculus. Unlike its better-known predecessor in Rome’s Pantheon, this round rooftop opening is protected from the elements, and its diameter varies from about 15 feet at its base to just under 10 feet at its top.
Below the conical skylight that protrudes through the building’s green roof is a multihued, powdercoated, perforated aluminum cone that serves as a heat sink. The heat sink’s form was “shaped by the sun,” Busby says. “The color is darker in the areas that are only hit by the summer sun—since you need to maximize the temperature differential to make the chimney effect work.” These darker areas are at the base of the heat sink, and are hit by the rays of the summer sun, increasing the temperature in the oculus to encourage airflow.
On summer days, operable windows in the sides of the skylight open and the heat-sink construct draws warm air through the building and exhausts it out through the vents. To the casual observer, the heat sink appears to be just another sculptural form in a building that’s packed with—indeed, composed of—them. But the multivalent device provides both a centerpiece to the visitor center and another place to start a conversation about how to make buildings work better with nature—an essential part of VanDusen’s mission and Busby’s sophisticated sustainable architecture.