The new visitor center at the Brooklyn Botanic Garden is cut into a tall berm and features a green roof. Photo by Albert Vecerka/Esto, courtesy of Brooklyn Botanic Gardens
The Brooklyn Botanic Garden opens an elegant new visitor center, cut into the side of a tall berm, with an extensive green roof and geothermal heating and cooling.
May 29, 2012—The Brooklyn Botanic Garden (BBG) recently unveiled a dramatic new visitor center, a sinuous steel and glass structure cut into a prominent berm on the 52-acre grounds, complete with a 10,000 sq ft leaf-shaped green roof that will serve as an experimental landscape.
The $28-million structure at 990 Washington Avenue serves as the main entrance to the garden, housing interpretative exhibits, a gift shop, and an impressive, leaf-shaped event space.
“The visitor center is both an extension and elevation of the garden’s topography, softening the transition from city to garden—and allowing us a significant new way to model how plants can fit into urban environments,” said Scot Medbury, the president of the Brooklyn Botanic Garden, in a press release. “It enhances BBG’s ability to welcome a growing audience and continues our longstanding commitment to fostering connections with our neighboring communities.”
The building was designed by the New York City architecture firm Weiss/Manfredi, with structural and civil engineering provided by Weidlinger Associates, also headquartered in New York City. The BBG invited several firms to submit ideas for the center, which in the Garden’s original master plan would have displaced a portion of a 25 ft high berm lined with a grove of mature ginkgo trees.
The leaf-shaped event space features high-performance, fritted
glass. Photo by Albert Vecerka/Esto, courtesy of Brooklyn
“A key aspect of why the Garden selected Weiss/Manfredi was our unique proposal, which shifted the building away from the center of the berm,” says Armando Petruccelli, the lead architect and project manager for Weiss/Manfredi. “The design of the building is conceived by Marion Weiss and Michael Manfredi, founding principals of Weiss/Manfredi, as an inhabitable topography that defines a new threshold between the city and the constructed landscapes of the 52-acre garden.”
This new gateway replaces a small turnstile installation that underwhelmed visitors entering from an adjacent parking lot and Washington Avenue. “The idea was to slide the building toward the street, give the garden visibility, develop an entry plaza, and then have a building that nests itself into the existing berm while simultaneously responding to the existing garden paths,” Petruccelli says.
The building is about 320 ft long and 60 wide at its widest point. It is divided into two distinct sections, separated by a covered breezeway. The retail pavilion, complete with a basement, is on the street façade. The reception pavilion, which contains an exhibit gallery, orientation room, and event space, is embedded in the berm and extends into the Garden.
Structurally, the building presented a challenge to Weidlinger engineers, not only because of its curved shape and long, narrow dimensions, but also because of the architectural design concept for the structural steel and concrete to be entirely visible.
“The architecture expresses the structure as a system and vice versa,” Petruccelli explains.
The new visitor center dramatically increases the garden’s
presence on Washington Avenue. Photo by Albert Vecerka/Esto,
courtesy of Brooklyn Botanic Gardens
This meant that the structure not only had to support the green roof—which seasonally varies in weight to as much 55 psf—but the joints had to be designed with full penetration welds, finished to a high degree.
“One unique requirement is around the perimeter of the building, where a C-12 channel defines the roof edge,” says Cheng Gu, Ph.D., P.E., M.ASCE, an associate at Weidlinger who worked on the project. “It has to be smooth, so we designed and fine-tuned the roof structure by dividing it into 29 gridline segments at various angles, with different lengths of cantilever. The longest cantilever was about 10 ft. We used a 3-D model to calculate the deflection at each roof edge to meet about a ¼ in. deflection under the varied loads. It deflects, but you don’t see it visually.”
The tight site, coupled with the nearby berm, required that a geoexchange system, comprising 28 six in. diameter wells—each 300 ft deep and housing a closed-loop geothermal tube—had to be placed beneath nearby paths at the facility. The tubes supply a heat pump system in the building’s cellar, reducing the structure’s overall energy consumption to heat and cool the interior spaces.
The building’s curved glass curtain walls make use of high-performance fritted glass to reduce solar heat gain and alert birds soaring throughout the garden to the presence of windows.
The undulating 10,000 sq ft green roof features 40,000 plants—grasses, spring bulbs, and perennial wildflowers—growing in 6 in. of media selected in part to reduce weight. Weiss/Manfredi collaborated closely with the New York City-based landscape architecture an urban planning firm HM White, the project’s landscape consultant, on the selection of plants, with input from BBG’s horticulture staff, to require as little water as possible and for multiseasonal aesthetics. The roof is part of an extensive system to collect and treat rainwater on-site.
“Storm-water runoff is managed on-site through the use of various green infrastructures,” says Jennifer Lee, P.E, A.M.ASCE, a senior engineer at Weidlinger. The runoff from the site’s impervious areas is collected and captured by the site’s storm-water management system through surface flow, roof leaders, underground pipes, and a stone-lined channel.”
The storm system’s green infrastructure—which includes a living green roof, two bioinfiltration basins, and secondary dry wells—works collectively to enable groundwater recharge, reduce runoff, and divert storm water from the city’s sewer system by means of evaporation, evapotranspiration, and infiltration, Lee says.
“In addition, storm-water quality is enhanced through the removal of pollutants, such as total suspended solids, nitrogen, and phosphorus,” she adds.
The BBG, an independent nonprofit institution, was founded in 1910. The city owns the property and supports operation with public funds. More than 12,000 types of plants can be found in the BBG, which accommodates approximately 725,000 visitors each year.