Monday, July 14, 2008

Green Roofs

Under Mayor Richard M. Daley's direction, the City of Chicago's Department of Environment took the initiative to start an aggressive green roof pilot project by hiring a team of landscape architects, architects, structural engineers, and ecologists to design and implement a green roof for Chicago's City Hall. Centrally located in downtown Chicago, City Hall is one of the most visible and recognized structures in the city. The primary purpose of the City Hall Green Roof Pilot Project is to provide a green roof demonstration that serves to facilitate research and educational outreach within the context of a midwestern climate.

Completed in 2001, the rooftop garden was designed to test different types of green roof systems, heating and cooling benefits, success rates of native and non-native vegetation, and reductions in rainwater runoff.

Although the rooftop is not normally accessible to the public, it is visually accessible from 33 taller buildings in the area. The design form is intended to be read from these various vantage points. The plantings are organized in a sunburst pattern, which respects the symmetry of the historic City Hall and provides a format for arranging groups of plants over the three different roof systems.

Rooftops are underutilized spaces in the urban environment, yet it is possible for any landscape, plaza, or garden to be installed on a building or structure. In Europe, over the past thirty years, rooftops have become the focus of a quiet but steady revolution through the application of green roof technologies. It is significant that properly designed green roofs can emulate natural processes. Even the thinnest green roof can effectively absorb most rainfall events, reverse the urban heat island effect, and provide wildlife habitat. They also insulate buildings, extend the life of the roof membrane, increase property values, and vastly improve urban aesthetics. While Europeans have been enjoying these benefits for years, Americans are just beginning to embrace them. Green roof technology is so new to America, that there is far too little data published to guide landscape architects in the design process.

No comments: