“Businesses should literally compete to be more ecological, not only on moral or ethical grounds or because it is "the right thing to do," but because such behavior squarely aligns with their bottom line.” - Paul Hawken, The Ecology of Commerce

Aquinas College

Green (or Vegetated) Roofs

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photo

The green roof of the 12-story Chicago City Hall building
Photo courtesy of Katrin Scholz-Barth (NREL PIX number 13397)

Green roofs are essentially a rooftop that is covered by a water-proofing layer, followed by a layer of soil and finally native plant(s), typically a variety of sedum. There are two types of green roofs, Intensive and Extensive.

Intensive green roofs are an older, traditional-style rooftop garden, with large trees and shrubs. They often are accessible to the public and can include garden paths, seating, and other features that make the roof more like a park. As suggested by the name, they are labor-intensive, requiring irrigation and continuous maintenance. Intensive roofs are multi-layer constructions, typically installed over concrete roof decks. They require substantial structural capacity: approximately 8 inches to 4 feet of soil depth, and support of roof weight loads from 80-150 pounds per square foot (University of Florida, IFAS Extension).

Extensive roofs, on the other hand, are not designed for public use but for environmental benefits. They help to mitigate the effects of storm water runoff by filtering, absorbing and/or detaining rainfall. Extensive green roofs can have a soil depth of approximately 1 to 7 inches and can carry weight loads of 15 pounds per square foot. They are constructed of a lightweight soil medium and are underlain by a drainage layer and a high quality impermeable membrane that protects the building structure. Extensive green roofs can be installed during the construction of a new building or retrofitted on existing roof decks. However, a structural engineer should always first inspect the structure to determine its weight load limitations. (University of Florida, IFAS Extension)

Green roof technology is somewhat new in the United States, but has been used for decades in other parts of the world. Germany has been developing the technology since the 1980ís and green roofs cover 150 million square feet in Europe (Environmental Design & Construction). Tokyo requires the use of green roofs on all new construction (Environmental Design & Construction). However, the use of the technology in the United States is drastically increasing everyday.

Green roofs are becoming one of the most effective green building measures as they do much more than mitigate the effects of urbanization on water resources. They also extend the life of the roof, keep the building cool in summer and warm in winter, provide wildlife habitat, reduce the urban heat island effect, provide a sound buffer, absorb carbon dioxide and create aesthetically pleasing green space amidst the surrounding concrete.

Michigan has seen quite an increase in the use of green roofs in new construction projects, as well as renovations. A few notable projects in the Grand Rapids area are as follows:

Here is a listing of green roofs in Michigan:

Check out the resources listed below for additional information on green roofs!

Links

Emory Knoll Farms

Emory Knoll Farms is a leading supplier of plants and plant expertise for extensive green roof systems. Their R&D pages offer access to University studies on green roof applications along with photo galleries from each project.

Green Building Pages

This site is a good source for information regarding cities and government entities that encourage sustainable building design & greenroof projects.

Green Roofs for Healthy Cities

Green Roofs for Healthy Citiesí mission is to increase the awareness of the economic, social, and environmental benefits of green roof infrastructure across North America and to rapidly advance the development of the market for green roof products and services.

Check out their site to learn more about green roofs, conferences and training courses in the arena of green design!

Green Roofs of Chicago

This site offers a wide range of interesting and informative links pertaining to Chicago's green roofs. It includes a description of Chicago's Rooftop Garden, first planted in 2000 on top of the 11-story City Hall building. The web site gives a description of the construction, design, and maintenance of the garden, and also includes many fascinating pictures.

Low Impact Development Center, Inc.

The Low Impact Development site provides visitors with lots of useful information on green roof technology, including an introduction, maintenance and cost information, benefits, pictures, and specifications.

MSU Green Roof Research Program

The Michigan State University site provides a variety of resources related to green roofs, including a basic introduction, research, funding, publications, photographs, and much more.

Penn State Center for Green Roof Research

This is a great site to learn the basics of green roofs or gather more detailed information on the technology. The Center's site lists benefits, provides information on recent research, news, publications, links, and brief case studies.

Funded by the Steelcase Foundation of Grand Rapids, Michigan
Header photo courtesy of The Environmental Protection Agency
Site by CMC/GrandNet