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Benefits of Green Roofs

As land continues to be replaced with impervious surfaces due to population growth and urbanization, the necessity to recover green space is becoming increasingly critical to maintain environmental quality.  Installing green roofs is one option that can reduce the negative impact of development while providing numerous environmental, economic, and social benefits.  They can improve stormwater management by reducing runoff and improving water quality, conserve energy, mitigate the urban heat island, increase longevity of roofing membranes, reduce noise and air pollution, sequester carbon, increase urban biodiversity by providing habitat for wildlife, provide space for urban agriculture, provide a more aesthetically pleasing and healthy environment to work and live, and improve return on investment compared to traditional roofs.

The mitigation of stormwater runoff is considered by many to be the primary benefit because of the prevalence of impervious surfaces in urban areas. Rapid runoff from roof surfaces can exacerbate flooding, increase erosion, and may result in raw sewage that is discharged directly into our rivers. The larger amount of runoff also results in a greater quantity of water that must be treated before it is potable. A major benefit of green roofs is their ability to absorb stormwater and release it slowly over a period of several hours. Green roof systems have been shown to retain 60-100% of the stormwater they receive. In addition, green roofs have a longer life-span than standard roofs because they are protected from ultraviolet radiation and the extreme fluctuations in temperature that cause roof membranes to deteriorate. Vegetation helps cool the membrane and the building during the summer as the plants and growing substrate act as an insulation layer, they shade the roof, and through evapotranspiration. Furthermore, the construction and maintenance of green roofs provide business opportunities for roofing contractors, plant producers, landscape designers and contractors, and other green industry members while addressing the issues of environmental stewardship.

Whittinghill, L.J. and D.B. Rowe.  2012.  The role of green roof technology in urban agriculture.  Renewable Agriculture and Food Systems 27(4):314-322.

Rowe, D.B.  2011.  Green roofs as a means of pollution abatement.  Environmental Pollution 159(8-9):2100-2110.

Rowe, D. B. and K.L. Getter.  2010.  Green roofs and roof gardens.  p. 391-412.   In: J. Aitkenhead-Peterson and A. Volder (ed.).  Urban Ecosystems Ecology.  Agron. Monogr. 55.  American Society of Agronomy.  Crop Science Society of America.  Soil Science Society of America, Madison, WI.

Oberndorfer, E., J. Lundholm, B. Bass, M. Connelly, R. Coffman, H. Doshi, N. Dunnett, S. Gaffin, M. Köhler, K. Lui, and B. Rowe.  2007.  Green roofs as urban ecosystems:  ecological structures, functions, and services.  BioScience 57(10):823-833.

Getter, K.L. and D.B. Rowe.  2006.  The role of green roofs in sustainable development.  HortScience  41(5):1276-1285.

A typical ugly commercial roof, grey in color.
A typical ugly commercial roof that provides no ecological, economic, aesthetic, or psychological benefits.

Flowering sedum and Allium, pink and yellow in color  Flowering sedum and Allium schoenoprasum on a roof in Amsterdam.Flowering sedum and Allium schoenoprasum on a roof in Amsterdam