The benefits of green roofs are many: longer roof lifespan, greater sound insulation, reduced heating and cooling system needs, and a cutback in storm water runoff. Green roofs decrease carbon dioxide and increase oxygen in cities, making them cooler in the process and reversing the so-called "urban heat island effect." In short, green roofs are the great green hope of many environmentalists, politicians, and architects interested in more efficient and environmentally aware buildings. From a design standpoint, however, there is less consensus. While some see the roof garden as a visual statement using plants, geometric lines, and sculptural elements, others believe concerns for sustainability should outweigh visual appeal. A green roof that combines aesthetics and mechanics has become the goal of many a landscape architect.
To address this quandary, the American Society of Landscape Architects (ASLA) commissioned renowned landscape architects, Michael Van Valkenburgh Associates in collaboration with the Conservation Design Forum to design a 3,300-square-foot green roof garden for its Washington, D.C. headquarters. In Green Roof Gardens, author Christian Werthmann uses this detailed case study to explain the history, methodology, and design process of green roof garden construction, providing a rich source of inspiration and technical knowledge for anybody interested in this simple solution to many of the environmental challenges we face today.