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Chicago, IL

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Under Mayor Richard M. Daley’s direction, the City of Chicago’s Department of Environment initiated 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 that would serve as the program’s demonstration project. Worn Jerabek Wiltse Architects served as the local architect on a team headed by Weston Associates.

The project was awarded the 2002 American Society of Landscape Architects Merit Award for outstanding site specific landscape solutions.


  • As part of the City’s Urban Heat Island Initiative, the 20,300 square foot green roof will help reduce the “Urban Heat Island Effect” and will serve as example for private and other governmental agencies. If green roofs are installed on 10% of Chicago’s rooftops, the overall temperature of the city can be reduced by 6-10 degrees on a hot summer day. For every degree the city temperature is lowered, the City can save $150 million.
  • By delaying and holding rainwater, City Hall’s green roof reduces the storm sewer loading by 70%.
  • Because the green roof protects the roofing membrane, the lifetime of the roof is estimated to increase by 50%.
  • Temperature and stormwater retention measurements are being compared between the City’s green roof and the County’s traditional black tar roof. The City is able to save approximately $4000 per year in heating and cooling costs at City Hall.
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