Redesigning the building for habitation by a new collection of animals presented its own set of challenges, and the conservation agenda of WCS called for an aggressive sustainability agenda. Strategies including materials recycling, on-site generation of electricity, water conservation, daylighting, and heat recovery all combined to earn the Lion House LEED certification—it is the first New York landmark building with this distinction.

Structure and Envelope

Renovation of the Lion House entailed reworking the building's envelope and structural system to accommodate new functions. Increasing the building's usable area from 32,000 to 40,000 square feet was largely accomplished by expanding the cellar level and creating new service space under the west terrace and the former cage area. This space is used for animal keeping, medical care, and life support systems.The 6,000 additional square feet on the lower level also contains service and mechanical areas and allows enough height for trees for the primates to climb. Floors, walls, and cage enclosures were removed and earth-moving equipment brought in to create greater depth inside the footprint of the building. "All this happened within the envelope of the original building, while having the exterior appear unaltered," says Sylvia Smith, a senior partner at FXFowle.

The most visible exterior changes took place on the east façade, which started as a ribbon of cages; these were completely stripped away. The new program required those walls to be solid, with a thick sandwich of insulation. Even so, FXFowle reinterpreted the façade in a way that evokes its original spirit. Along its recessed sections, tubular steel columns are exposed to re-establish the structural rhythm. The columns rest on a reconstructed parapet wall made of reused bricks and a recycled-granite water table, topped with a new limestone sill. Space between the columns is infilled with ironspot bricks recovered from other parts of the building. The three projecting volumes are wrapped with ornamental iron grilles that recall their former use as cages. Behind the grilles are stainless steel panels etched with graphics of the Madagascar landscape. The effect changes with the daylight conditions.

Existing Conditions and Program

The Lion House is the largest building on Astor Court, a collection of Beaux-Arts structures that was designated a National Historic District by the New York City Landmarks Commission in 2000. "In some ways, it is the symbolic heart of the zoo," says Susan Chin, director of planning and design for WCS. The original façade was composed of limestone, Roman ironspot brick, a copper roof, and a cornice of terra-cotta medallions embellished with puma, jaguar, and leopard heads. Sculptor Eli Harvey designed the medallions and the lifelike stone lions that adorn the structure. The interior was organized as a long hall with cages to one side and large, round-headed windows to the other.In striving to create a program that would fit the building, the staff faced the inherent limitation of the original floor plan its strong linear orientation. The small scale of most Madagascan wildlife seemed to fit an immersive exhibit, but it soon became clear that such animals take up more room than expected. "You quickly learn that it's not only about exhibit space—it's all the back-of-house functions that support the animals and plants," says Smith. The design team was challenged to accommodate 4,800 square feet of exhibit program, 6,700 square feet of wildlife support space, and 6,700 square feet of mechanical space within the existing envelope.

Interior Reorganization

While the architects strove to stay as true as possible to the Lion House's original exterior, avoiding significant alterations to the interior was impossible. The close collaboration between the architects and zoo staff also required a shift in attitude. "As architects, we are so used to understanding what human beings need," says Chin, who is trained as an architect herself. "When you switch to a different species, you have to reinvent the way you think." Visitors entering from the south leave the familiar world behind and pass into an immersive environment designed to simulate the Madagascar landscape. The pedestrian path weaves along a serpentine route past the Tsingy Forest exhibit, where rare primates known as Coquerel's sifakas swing from tree to tree, and the Nile crocodile cave, where visitors encounter an 800-pound crocodile.Wedged between and beneath the exhibits is a complex maze of access ways for the animals, which are removed to holding areas each night. "The holding space is very important," says Smith, noting that not only do the animals need to be secured at night, but the exhibits need a break from the animals' tendency to devour plants. Along with animal holding areas and a large mechanical room, this level includes life support systems for the crocodiles and sea lions (which frolic in an outdoor pool on Astor Court) and space for a gigantic fuel cell. The former viewing hall is refurbished as a multipurpose space called the Schiff Family Great Hall. The openings left by cage removal are covered by infill panels. Its original skylights were rebuilt and the battened ceiling rebuilt with concealed acoustical panels, leaving the ceiling plane open to showcase the old cast iron trusses that spring from side to side. Flooring in the hall is a raised system of concrete pavers, which allows conditioned air to be circulated in the plenum beneath and eliminates the need for visible ductwork in the ceiling.

Sustainable Systems

The onus placed on the architects and engineers to make the building highly energy-efficient created opportunities to imbed a wide range of technologies. The most innovative of these are the skylights, a three-layer ethylene tetrafluoroethylene (ETFE) system with a movable center layer and staggered shading patterns that balance the requirements of maximum natural light with minimum heat gain as well as electrical and cooling loads.Inadequate underground electrical distribution on the campus helped make a fuel cell an economical choice. Excess energy will be exported to the zoo grid. In addition, waste heat from the fuel cell will supply some 40 percent of the building's heat. The active participation in the design process of both WCS and the New York City Department of Design and Construction allowed the team to explore alternatives to standard definitions of comfort. After all, the animals like to be warm, while people prefer to be cool. Right-sizing the HVAC system included controlling exhibit lighting and skylight shading through the building automation system, which also monitors and controls the sources of heat and reheat to achieve the most energy-efficient result. "We ended up agreeing that on the hottest days of the summer, people don't have to walk through here and expect it to be 72 degrees," Smith says.

Project: Lion House Reconstruction at the Bronx Zoo, New York
Client: New York City Department of Design and Construction
End User: Wildlife Conservation Society
Architect: FXFowle Architects, New York—Sylvia Smith (senior partner); Thomas N. Fox, Paul A. Tapogna, Krishna Rao, Danny MacNelly, Mark Ruzitsky, Nicholas Tocheff, Conrad Talley, Jeremy Geddes, Chad McKee, Sean Murphy, Heng-Choong Leong, Nicholas Hollot, Susan Masi (project team)
Historic Preservation: Building Conservation Associates Inc.
Landscape Architect: Quennell Rothschild & Partners
Lighting Consultant: Hayden McKay Lighting Design
Structural Engineer: Anastos Engineering
M/E/P Engineer: Kallen & Lemelson Engineers
Acoustic Consultant: Cerami & Associates
Geotechnical Engineer: Langan
Exhibition Design: Exhibition and Graphic Art Department, Wildlife Conservation Society
Life Support System Design: TJP Inc.
Construction Manager: Hill International
Habitat Fabrication: Cost of Wisconsin
Graphics Fabrication: Dimensional Communications
Exhibit Murals: Dave Rock
Size: 40,865 gross square feet


Skylight System

Foiltec North America

The need for ultraviolet radiation for the animals mandated large skylight areas with good solar transmittance?the exact opposite of what is required for reduced energy consumption and reduced A/C capacity. The Texlon Foil System, an ethylene tetrafluoroethylene (ETFE) membrane skylight by Foiltec, proved to be the solution to controlling sunlight and modulating heat loss and heat gain. Variable air pressure inside the system controls the position of the ETFE's center layer to provide shading when needed. This new technology, with an R-value of 3.3 (as opposed to 1.8 for a conventional polyester film skylight) covers nearly 8,500 square feet of roof.

Stainless Steel Panel System

Rimex Metals Group
To create new interior exhibition space, the Lion House's exterior cages were enclosed with stainless steel rainscreen panels manufactured by Rimex Metals (UK). To lend interest to the metal surface, the zoo's graphic arts department created large-scale graphics simulating the Madagascan jungle landscape. The subtle design was etched and bead-blasted into the steel surface by Rimex before shipment to the site.

Fuel Cell

United Technologies
A 200-kilowatt fuel cell provides electricity for the building using natural gas as its fuel source. Because it operates constantly, the fuel cell produces excess energy during off-peak times; this is exported to the zoo campus electrical grid. The fuel cell is expected to supply at least 50 percent of the Lion House's electricity need. Up to 650 MBTU/hr of waste heat from the cell is expected to meet approximately 40 percent of the building's heating requirement.

Life Support Systems

Engineering design by TJP Inc.

The building's cellar houses equipment to purify water in the crocodile tank inside the Lion House and in the exterior sea lion pool on Astor Court. In the case of the sea lion pool, the new system eliminates the need for routine water changes, conserving about 160,000 gallons of water each week and saving the East River from receiving the wastewater.