The Thoreau Center adapted seven remaining structures of the Letterman Hospital, which was constructed between 1899 and 1902, into modern day office space for up to 60 nonprofit organizations at one time.
Credit: Richard Barnes
About 150 years ago, Henry David Thoreau wrote that "in Wildness is the preservation of the World." This thought still resonates today with the different kind of preservation on display at San Francisco’s Thoreau Center for Sustainability. Since 1996, the restored 150,000-square-foot complex on the grounds of the Presidio of San Francisco, part of the National Park Service’s Golden Gate National Recreation Area, has been home to as many as 60 nonprofit organizations at the same time, all devoted to environmental and social justice issues.
Located in the historic wards of Letterman Hospital, which was constructed between 1899 and 1902 and was the U.S. Army’s largest hospital by 1918, the center has served as a model for redevelopment and innovative public-private partnerships. Equally important, the rehabilitation of the site’s 12 two- and three-story buildings presented an early prototype for combining preservation and sustainable design principles, transforming historic buildings into economically viable office space for the future. The National Trust for Historic Preservation recognized this accomplishment in 1997 with an Honor Award, while the AIA’s Committee on the Environment named it one of its Top Ten Green Projects for 1998.
In rehabilitation the old hospital, open office layouts presented an acoustical challenge, particularly because of the hard plaster surfaces in the historic structures. Also, many occupants wanted traditional, private offices. LMS continues to address this through close attention to acoustic treatments.
Credit: Richard Barnes
By the 1960s, much of the original hospital had fallen into disrepair and was badly in need of major MEP and life-safety improvements, and in 1969 the U.S. Army demolished all but eight structures. The remaining facilities—the original three-story, wood-frame headquarters, three adjacent concrete buildings, and four wood buildings—were placed on the National Register of Historic Places in 1962.
Reconstruction was divided into two phases, with the first phase rehabilitating the headquarters and adjacent concrete buildings and the second phase rehabilitating the four wood buildings. The historic registration of the existing facilities played a dominant role in transforming the older structures into new office space. As a historic landmark, all building upgrades had to conform with the Secretary of the Interior’s Standards for the Treatment of Historic Properties, published in 1992. The National Park Service also expected systems and materials to meet its Guiding Principles of Sustainable Design, published in 1993.
As a result, the current design by San Francisco–based Leddy Maytum Stacy Architects (LMS) retains the hospital’s original circulation and general plan. Enclosing the original porte cocheres—entry porches originally used for ambulance arrivals—on two of the concrete ward buildings created new tenant space. Concealed mullions were approved to infill these areas. The north corridor connecting all the buildings now serves as the main connector for all the organizations operating within, and a shared café and conference facilities are now the buildings’ social center. A photovoltaic array, not so common in 1996, was built into the entryway of the main building and provides about 8kWh of power per day, which is fed back into the grid. These changes also meet another project requirement: Federal standards dictate that architectural features must follow "reversible" design practices without damaging the original structure should a building’s use change again in the future. On this note, the original tile covering the buildings’ interiors, which posed acoustical problems, was not removed but rather was carefully covered with drywall.
Spread over multiple wings, the center features high-efficiency lighting, heating, and cooling systems, as well as formaldehyde-free paints, cotton batt insulation, and sustainably harvested wood paneling. Recycled material includes bathroom tiles made from recycled car and airplane windshields and recycled aluminum storefronts for the interior offices and exterior porte cocheres.
As originally designed, the hospital wards relied on narrow floor plates and abundant access to exterior windows. This layout made the structures ideal candidates for exploiting daylighting and natural ventilation. "One of the great lessons of the Thoreau Center is what these buildings had to offer," recalls Marsha Maytum, FAIA, principal at LMS. "The buildings were designed in a sensible way, so there was fresh air and everybody had access to natural light because they didn’t have the ability to artificially ventilate or rely on electricity." Cross-ventilation combined with operable windows and attic roof vents helps circulate air naturally.
The center’s first phase, comprising 75,000 square feet, was completed in 1996, while the 75,000-square-foot second phase was completed in 1998. Today, tenants include the World Wildlife Fund and the Tides Foundation, among others. The Tides Foundation, along with Equity Community Builders, led the original redevelopment effort.
Maytum returns to the Thoreau Center periodically to consult on refreshing interior spaces or to ask about the buildings’ performance. She recalls how compelling the idea seemed more than 15 years ago. "When it became clear the U.S. Army was going to turn the Presidio over to the National Park Service, the Tides saw this as a great opportunity to take the idea of ‘beating swords into ploughshares’ and create this new type of community resource," she says. "At the time the Thoreau Center opened, there were only three multitenant nonprofit centers in the country, according to the Tides Foundation. There was such a great interest in what had been achieved, the Tides created a whole nonprofit center network and is now a thriving organization. By 2001, there were eight of these centers, and in 2011 there are now more than 250. This idea of a shared center for like-minded organizations has become a powerful model."
David R. Macaulay is the author of Integrated Design: Mithun and the blog, Green ArchiText at greenarchitext.com.