In some cases, respondents were simply wrong about what green roofs do. For instance, when asked what impact the vegetation on a green roof has on air quality, nearly 70 percent indicated that "it helps filter dust and dust particulates from the air," which studies show is incorrect. and about 7 percent responded that green roofs actually harm indoor air quality. On the contrary, like most vegetation, the plants on a Green roof absorb pollutants from the air and release oxygen.
Asked how green roofs affect outdoor air temperatures, 17 percent of repondents said they have "little or no effect." But one of the most significant, proven benefits of green roof systems is that they help reduce the “urban heat island” effect -- the reason inner cities and large downtown areas are considerably warmer than outlying, forested areas.
Among the other responses to the survey: Forty-one percent thought the most significant benefit of a Green roof is energy savings. Although they do help “insulate” a facility, which does reduce energy costs, the key benefit of a Green roof is their ability to reduce stormwater runoff. As to costs, more than 70 percent of the respondents were aware that a modular Green roof, where plants are preplanted in modules that are placed atop the existing roof, tends to be less expensive than a built-in-place system constructed directly on the roof. Nearly 60 percent of the respondents believed a Green roof increases the value of a property, whereas about 40 percent believed the technology is too new to affect property values. Green roofs are recognized as a property improvement and can increase property values.
Similarly, only 30 percent believed a Green roof increases the life cycle of the existing roof, while the other respondents believed it has little impact. In actuality, studies find that Green roofs can double the life expectancy of the existing roof. Less than a third of the respondents knew that a Green roof can contribute seven points or more toward LEED certification. Most of the other respondents believed it was five points or less or that it was not part of the LEED accreditation evaluation.
Finally, the facility managers were asked what U.S. city has the most Green roofs installed. Most respondents were sure it was either Portland, Oregon, or Seattle, Washington. However, the city with the most Green roofs installed, by a fairly wide margin, is Chicago. With two million square feet of Green roofs installed, including one on their City Hall, it appears Chicago may have to do a bit more boasting about how Green the city is becoming.
Posted on 9th May 2007
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