Green Design at the US Coast Guard Headquarter
by Jackie Craven, Updated March 08, 2017
Coast Guard Green at St. Elizabeths
The U.S. Coast Guard Headquarters has a green roof. Built into a hillside in SE Washington, D.C., the Headquarters is said to have one of the largest Green Roof Systems in the U.S. Architects have designed an ecosystem that captures both the sun and the rain, allowing government workers natural light and the professionally-designed landscape to be irrigated by collected stormwater. At project's end, the ponds became less muddy, the vegetation more lush, and office workers less stressful.
The site chosen to develop the new U.S. Coast Guard Headquarters was not only a contaminated brownfield, but also an undesirable hillside—the elevation dropped 120 feet. Clark Construction explains:
"The 1.2 million square-foot, 11-level office building is the central component of the 176-acre campus, as well as its most unique element. The structure is built into the sloping hillside and only two of the levels are entirely above-grade. The lower nine are built into—and extend out from—the hillside. The building consists of linked, quadrangles, clad in brick, schist stone, glass, and metal that follow the site's natural change in elevation and cascade toward the Anacostia River."
Building into the hillside not only provided energy efficiency for campus buildings, but also aesthetically realized Frank Lloyd Wright's concept of organic architecture by becoming part of the natural environment. The redevelopment of the west campus of St. Elizabeths, the National Historic Landmark asylum, was as big a project as building the Pentagon in 1943.
Modern Green Roofs are built with many layers, including waterproofing, as explained in Green Roof Basics. For the USCG Headquarters, the design/build team decided to create a waterproof membrane with hot rubberized asphalt. "The original spec for the Vegetative Roof Assemblies® (VRA) included a single-source warranty by the primary waterproofing/roofing manufacturer," says Todd Skopic of Henry Company, the VRA's manufacturer. "The project team decided to have the primary waterproofing/roofing manufacturer be responsible for the waterproofing system, and the roofing contractor be responsible for the vegetative components." Skopic also points out that specifications for the growing media (Rooflite®) were "adjusted in order to reduce the loads to within the structural tolerances for the roof structure."
The Rooflite was either crane-hoisted to the roofs or blown onto the roof with large pneumatic hoses. "Hardy Sedum mats are planted around the perimeter of most of the roofs," says Todd Skopic. "The effect of the Sedum mats at the roof perimeter provides a neat and tidy edge to the wilder grasses and shrubs in the mounded areas in the middle."
Onsite decisions and specification changes are realities on many building projects, but sometimes problems arise. One immediately thinks of Frank Gehry and Disney Hall, when contractors used too-shiny, heat-reflecting stainless steel panels that were not Gehry's specifications—a costly error in judgement. When a Green Roof doesn't work out, the problem is not always with the system but the installation.
The architectural design of the Washington. D.C. Coast Guard Headquarters is specific for this site. The buildings and landscaping are both integrated into the hillside, as an extension of the land. The upper levels look over the Anacostia River, just before it joins and continues its journey into the Potomac River. This approach of integrating man-made architecture with the natural environment is similar to architect Frank Lloyd Wright's notion of organic architecture.
Kim A. O'Connell, writing for AIA Architect, makes note of the architecture "cascading down the hill almost as if Frank Lloyd Wright had transposed Fallingwater into a million-square-foot government facility." O'Connell notes this design trend as a welcome departure from other publicly-funded buildings:
"The building's contextual and sustainable approach to both land and water represents a marked departure from the way federal buildings were planned and sited in the past, a trend that resulted in the many monolithic, inwardly focused mid-century Modern structures that line the core of the capital city."