Green Roofs: Using Roofs for More Than Keeping Dry

Mayor Richard Daley saw his first planted roofs several years ago while visiting Chicago’s sister city of Hamburg, Germany. At the same time, he was learning about urban heat islands (in which our urban areas maintain temperatures considerably higher than surrounding suburban and rural areas). He was particularly attuned to the urban heat island problem because a few years earlier, several dozen elderly residents had died during a Chicago heat wave. Perhaps because of that situation, Chicago had been selected by the U.S. Environmental Protection Agency (EPA) as one of five cities for urban heat island pilot projects.

Daley saw in Hamburg’s green roofs an opportunity for Chicago and proposed a demonstration project on City Hall—which was due for a new roof. This would be an excellent opportunity to see if this innovative roof system made sense. Would it help reduce the “urban heat island” problem? Would it save energy for the City? Would it reduce stormwater flows into the city’s combined sewer system that all-too-often dumps raw sewage into Lake Michigan? Roy F. Weston, Inc. was hired to research and coordinate the green roof project in 1999, and they selected a team of William McDonough + Partners, landscape architects Conservation Design Forum, and green roofing consultants Roofscapes, Inc. The project was completed early this summer. While it is still too early to assess performance, already the project has propelled green roofs into public view.

When EBN first addressed green roofs—as part of the November 1998 (Vol. 7, No. 10) feature on low-slope roofing, American Hydrotech and Soprema were the only companies with integrated green roof products available in North America. There were just a handful of vegetated roofs here that were serving to demonstrate this innovative green-building strategy. Today, barely three years later, a wide array of green roofing systems exist, along with a cadre of specialized designers, consultants, installers, and suppliers.

This article looks at the recent history of green roofing, summarizes the environmental benefits of green roofs, and describes green roofing products available today. Lightweight and stylistically flexible, these new green roofs can be integrated into commercial, institutional, and residential buildings—most commonly on low-slope roofs.