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.
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.
Lessons Learned
The adaptive reuse of the old Letterman Hospital stands as a model for protecting architectural and cultural resources while creating an enriching space for current tenants. Ultimately, says Marsha Maytum, FAIA, principal of San Francisco–based Leddy Maytum Stacy Architects (LMS), the project team’s goal was “to prove it was possible to integrate sustainable design strategies and transform the use of these buildings in a way that did not compromise their historic integrity because they were national landmarks.”
With the LEED rating system still in its pilot phase at the time of the center’s construction, architects were just beginning to explore the intersection of historic preservation and sustainable design. Maytum offers these key lessons learned through work on the Center:
• Continue to press for the use, and approval, of truly green materials. During predesign phases in 1994, the project’s biggest challenge became identifying low-VOC paints and carpet and other eco-friendly materials with suppliers, and then convincing local reviewing agencies to approve materials such as cotton batt insulation as a viable element of the building rehabilitation.
• Seek solutions that merge preservation with sustainaility. The center illustrates the possibilities of adaptive reuse by integrating sustainable design without compromising the attributes of a historic landmark. An overarching goal for the project’s two developers, Equity Community Builders and the Tides Foundation, is to sustainably transform existing community resources into spaces that are appropriate for important uses today.
• Balance the need for privacy with open office plans. Maximizing daylighting and cross ventilation implies an open office layout, yet this presented an acoustical challenge, particularly in historic buildings with hard plaster surfaces. Also, many occupants expressed a desire for traditional, private office settings. LMS continues to address this through close attention to acoustic treatments, while ensuring that each program incorporates private and shared private spaces.
• Integrated design processes and tools are still evolving. “The tools available now to predict performance and understand daylighting has been a great development in how we can design sustainably and work as an integrated team in the early design phases and communicate what we’re doing with our clients,” Maytum says.
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.