For GSS Energy Use chapter 8. Excerpt: Looking strictly at the economic costs and benefits of three different roof types—black, white and “green” (or vegetated)—Lawrence Berkeley National Laboratory (Berkeley Lab) researchers have found in a new study that white roofs are the most cost-effective over a 50-year time span. While the high installation cost of green roofs sets them back in economic terms, their environmental and amenity benefits may at least partially mitigate their financial burden. ...“We leave open the possibility that other factors may make green roofs more attractive or more beneficial options in certain scenarios,” said Mandel, a graduate student researcher at Berkeley Lab. “The relative costs and benefits do vary by circumstance.” However, unlike white roofs, green roofs do not offset climate change. White roofs are more reflective than green roofs, reflecting roughly three times more sunlight back into the atmosphere and therefore absorbing less sunlight at earth’s surface. By absorbing less sunlight than either green or black roofs, white roofs offset a portion of the warming effect from greenhouse gas emissions. ...black roofs pose a major health risk in cities that see high temperatures in the summer. “In Chicago’s July 1995 heat wave a major risk factor in mortality was living on the top floor of a building with a black roof,” Rosenfeld said.... http://newscenter.lbl.gov/news-releases/2014/01/21/white-green-or-black-roofs-berkeley-lab-report-compares-economic-payoffs/. Julie Chao, UC Berkeley News Center.
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