Date of Award
Dr. Travis J. Ryan
Not your basic rooftop garden, green roofs contain growing media and are planted with various types of vegetation. Green roofs can be either intensive, with soil depths above 6 inches and increased size and attractiveness of vegetation, such as trees and shrubs, or extensive, with soil depths between 2-6 inches and low, moss or grass-like plants that require little care (Getter et al. 2009, Indianapolis DPW 2008, Obemdorfer et al. 2007, US DOE 2004).
Although green roofs are initially more expensive than traditional roofing techniques due to the cost of additional materials, the long-term cost savings are high and can provide a retum on investment (Carter and Keeler 2008, Indianapolis DPW 2008, US DOE 2004). With the growing popularity of green roofs in the United States, these costs are going down. In Germany, where green roof technology has been established for 30 years, prices for green roof construction are as low as 50% that of conventional roofs (www.greenroofs.com). Several cities, especially in Europe, are adopting regulations for the incorporation of green roofs onto portions of their buildings. In Basel, Switzerland, research on the biological conservation potential of green roofs has contributed to the 3 city's new strategy of mandating the installation of green roofs on all new buildings with flat roofs (Brenneisen 2006).
Retrofitting an existing structure with a green roof is also an increasingly common approach. Flat roofs are generally the best candidates for this construction because they often do not necessitate additional support for the low extra weight of an extensive green roof, and they require little expertise in their installation (Carter and Keeler 2008). A good candidate roof for retrofit installation should be expected to hold an extra 15-25 pounds per square foot (psf) (Indianapolis DPW 2008). Rock ballast roofs generally weigh 10-15 psf, and would be replaced with an extensive green roof that could weigh 10-35 psf saturated (Indianapolis DPW 2008). If changes to the roof structure are necessary, these can include additional decking, roof trusses, or joists (Indianapolis DPW 2008). Incorporating a green roof onto any building provides a multitude of environmental and economic benefits, such as lowered heating and cooling costs, carbon sequestration, decreased air and noise pollution, reduced urban heat island effects, stormwater management, increased lifetime of roof membrane, presence of a more aesthetically pleasing area, and increased urban biodiversity (Getter et al. 2009, Obemdorfer et al. 2007, Altor 2010).
Strobl, Sarah Elizabeth, "Teaching old buildings new tricks: benefits of retrofitting Indianapolis buildings with green roofs" (2012). Undergraduate Honors Thesis Collection. 176.