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Case Study:
Plaza Apartments

San Francisco, CA

A Room of One’s Own: In the heart of San Francisco's skid row, once-homeless adults find shelter in a showplace of green design.

By Joann Gonchar, AIA

A new residential building in a still-rough section of San Francisco’s South of Market neighborhood is helping satisfy a set of ambitious social and environmental goals. The $22 million Plaza Apartments, open since early 2006, is one of the city’s first green affordable housing projects. It incorporates sustainable materials, on-site power generation, and strategies to ensure good indoor air quality. It is designed to achieve a 25 percent energy savings over a building that complies with California’s already-tough energy standard, Title 24.

Plaza Apartments
Photo © Tim Griffith

Plaza Apartments

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KEY PARAMETERS
San Francisco (Vista Grande watershed through the San Francisco Canal)
GROSS SQUARE FOOTAGE: 56,800 ft2 (5,277 m2)
COST: $22 million
COMPLETED: January 2006
ANNUAL PURCHASED ENERGY USE (BASED ON SIMULATION): 58 kBtu/ft2 (660 MJ/m2) ANNUAL CARBON FOOTPRINT (PREDICTED): 11 lbs. CO2/ft2 (54 kg CO2/m2)
ROGRAM: Studio apartments, mental and physical health-care facilities

Sky Conditions   Temp./Dew Points   Heating/Cooling
Sky Conditions   Temp./Dew Points   Heating/Cooling

TEAM
OWNER: Public Initiatives Development Corporation
ARCHITECT/INTERIOR DESIGNER: Leddy Maytum Stacy Architects and Paulett Taggart Architects
ENGINEERS: OLMM Consulting Engineers (structural); Telamon Engineering Consultants (civil); CB Engineers (mechanical); POLA Design & Engineering Services (electrical)
COMMISSIONING AGENT: Timmons Engineering
BUILDING ENVELOPE CONSULTANT: Simpson Gumpertz & Heger
ENERAL CONTRACTOR: Nibbi Brothers


SOURCES
METAL/GLASS CURTAINWALL: Kawneer
WOOD EXTERIOR CLADDING AND RAINSCREEN PANELS: Parklex
WINDOWS: PPG, Solexia, Industrex, Superlite II
DOORS: Marshfield Signature Series, FSC Certified (wood); Forderer Cornice Works (metal)
ROOFING: Johns Manville
PAINTS AND STAINS: ICI Dulux Lifemaster 2000 Interior, No VOC paint; Minwax (wood stain), L&M Construction Chemicals Dress & Seal WB, Concrete Graffiti Control, Prosoco Graffiti Barriers Block-Guard, low VOC
LIGHTING:  Indessa, Prudential, Delray, Lightolier, Vibia, BK Lighting, Kim
CARPET: Tandus Collins & Aikman, Patcraft EcoSol
FURNISHINGS: Steelcase, Ecodura, Brayton, Howe
PHOTOVOLTAIC PANELS: Mitsubishi
RESIDENTIAL BATHROOM FLOORS: Nora Rubber
CASEWORK WHEATBOARD: Dow Woodstalk

First conceived as an apartment building for very low-income San Franciscans, the project was reconfigured in a late stage of construction—after eight of its nine-story exposed-concrete structure had been poured and much of the mechanical systems installed—to provide permanent housing for the chronically homeless. After the shift in program, designers maintained the layout of the 106 studio apartments but were required to provide spaces for additional staff, such as social workers and health-care professionals. “Our goal is to provide everything residents need for fully independent living,” says Erin Carson, the former project manager for the building’s owner, the Public Initiatives Development Corporation (PIDC). The service staff grew from two to 10 people, according to Carson, now a development specialist with the parent organization of PIDC, the San Francisco Redevelopment Agency.

Despite the many support services offered on-site, the Plaza has a decidedly non-institutional flavor. The building’s upper stories are clad in composite panels in a variety of earthy hues. The street level includes retail space and a lobby for a below-grade black-box theater to be leased by a Filipino performing arts company, which occupied the decrepit 1920s-era building formerly on the site at Sixth and Howard streets. “One of the goals of the project is to improve the neighborhood without displacing tenants,” says Richard Stacy, AIA, principal of locally based Leddy Maytum Stacy Architects. His firm, in association with Paulett Taggart Architects, also of San Francisco, designed the building.

Residents enter the Plaza Apartments through a leafy courtyard leading to a double-story entry hall flanked by administrative offices and a community room. The warm tones of bamboo floors, sustainably harvested cherry veneers, and ochre-colored walls contrast with exposed concrete and slate.

A typical residential floor contains 14 apartments, each a very compact 280 square feet, including a kitchenette and bath. The units are arranged in pinwheel fashion around the building’s central core.

The organization allows for windows and ventilation louvers at the end of each common corridor, providing daylight, views, and fresh air—amenities that are particularly valued given the building’s density, points out Carson.

Apartment finishes are simple and durable, including formaldehyde-free wheat-board casework, linoleum kitchen floors, and paints without volatile organic compounds. On the assumption that the carpeting would need to be entirely replaced whenever a resident moved, the architects chose a rolled material with a high percentage of recycled content. For the corridors, they selected carpet tiles so that maintenance staff could easily replace stained or worn portions.

On the exterior, the corridor windows create a vertical slice through each facade, interrupting the exposed structural grid established by the width of each apartment. Within this grid, high-performance operable window walls alternate with the composite panels made of recycled craft paper, wood veneer, and resin. These panels, part of an open-jointed rainscreen facade system, provide a number of performance advantages, according to Stacy. For example, the wall assembly includes batt insulation between studs as well as a layer of rigid insulation on the outboard side of the framing, enhancing the thermal properties of the building envelope. In addition, the approximately 1-inch cavity between the panels and the building’s weather-resistant barrier allows air to circulate behind the facade, mitigating solar gain, he says.

Concern about solar gain was one of the reasons the architects gave slightly different expression to each facade. On the southwest side of the building, the panels are flush with the structure, but the windows are recessed, providing shading from the hot afternoon sun. However, on the southeast facade, where thermal gain is less of a worry, the relationship is reversed. In addition to tuning the facades to their respective orientations, the configuration creates subtle variations in the play of light, shadow, and materials.

On the roof is a 28-kilowatt photovoltaic (PV) array that generates about 5 percent of the Plaza’s power needs. To provide this amount of electricity, the building’s compact roofscape is almost completely covered with PV panels, creating a logistical challenge for the mechanical engineer, who needed to provide clearance for the many plumbing vents and bathroom fans and ensure access to mechanical equipment. “The roof is just jam-packed,” says Chikezie Nzewi, project engineer for CB Engineers, San Francisco, the building’s mechanical consultant.

Given San Francisco’s temperate climate, mechanical cooling was deemed necessary only in the retail area and the theater. Those spaces are served by water-cooled heat pumps that receive condenser water from a roof-mounted cooling tower. A radiant hot-water system provides heating for most of the remainder of the building. Two natural-gas-fired boilers with thermal efficiencies of 85 percent generate the hot water, and pumps with variable-speed drives circulate it throughout the building.

Nzewi credits close coordination among team members for achieving the best layout for the hydronic system’s infrastructure. He worked with the designers to precisely locate each radiator, saving an enormous amount of piping and making a comfortable furniture arrangement possible in the tight apartments. “Usually architects just provide an open shaft,” he says.

Because California code limits permissible noise transmission levels from outside to inside, the designers provided another apartment ventilation source in addition to the operable windows. Through-wall Z-shaped transfer grilles let in outdoor air but prevent the transmission of traffic noise and other street sounds into the residences, while the bathroom “scavenger” fans provide constant low-level air changes. “From an energy standpoint, the arrangement is a bit of a negative, but it does provide for good indoor air quality,” says Stacy.

The project team has registered the Plaza Apartments for Leadership in Energy and Environmental Design (LEED) certification through the U.S. Green Building Council and has targeted a Silver rating. However, certification now hinges on the outcome of a soon-to-be-conducted blower door test to demonstrate minimum air leakage from one apartment to another or into the common corridors. The test is part of an alternate compliance path to a LEED prerequisite regarding tobacco smoke.

Whatever the outcome of the test, team members say they have found value in the certification process. The need to demonstrate compliance helped ensure that performance goals were met. “A lot of things just won’t get done if you don’t go through certification,” says Paulett Taggart, FAIA. She credits the documentation process with helping the team even exceed some of the goals established at the project’s outset. For example, the contractors recycled almost 90 percent of the demolition debris even though the official requirement was only 75 percent. “I don’t think we would have achieved that if there wasn’t someone keeping a close watch,” she says.

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This article appeared in the July 2007 print issue of GreenSource Magazine

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