White and green roofs can save energy, combat global warming

 

Feb 11, 2014 - Brooks Hays - Upi.com

(L to R) District of Columbia Mayor Adrian Fenty, Mikayla Kelly, age 3 of Maryland, U.S. Department of Housing and Urban Development Secretary Shaun Donovan and D.C. Housing Authority Director Michael Kelly participate in a planting ceremony on a D.C. 'green roof' in Washington on April 22, 2009. (UPI Photo/Kevin Dietsch) | License Photo
(L to R) District of Columbia Mayor Adrian Fenty, Mikayla Kelly, age 3 of Maryland, U.S. Department of Housing and Urban Development Secretary Shaun Donovan and D.C. Housing Authority Director Michael Kelly participate in a planting ceremony on a D.C. 'green roof' in Washington on April 22, 2009. (UPI Photo/Kevin Dietsch)
| License Photo

WASHINGTON, Feb. 11 (UPI) -- The transition of world populations to urban centers means more black, heat-absorbing roads, trees being replaced by buildings, and the use of large amounts of concrete in concentrated areas. This reality, known as megapolitan expansion, is a significant driver of global warming.

But a new study by a team of three scientists with the U.S. Environmental Protection Agency suggests adaptive measures like painting roofs white or installing rooftop gardens can offset atmospheric warming from urban expansion.

Statistical models developed by the research team project that megapolitan expansion could raise surface temperatures by as much as six degrees Fahrenheit in some cities. But the models also contend that white and green roofs, if effectively employed, can not only offset such increases, but could potentially counteract the consequences of greenhouse gas emissions.

"Urban adaptation can roll back warming of emerging megapolitan regions," the study, which was published in the Early Edition of the Proceedings of the National Academy of Sciences, claims.

White and green roofs aren't created equal in terms of their climate change mitigation abilities, however. The study found that white roofs would have a much more profound cooling and energy-savings effect in the South, compared with northern megapolitan regions.

In northern climes, white roofs prove less effective as a year-round energy-saving solution because they also encourage cooler temperatures in the winter, requiring additional heating to maintain comfortable conditions. Green roofs, although they don't provide the same level of cooling in the summer, help keep buildings slightly warmer in the winter.

"The energy savings gained during the summer season, for some regions, is nearly entirely lost during the winter season," said Matei Georgesce, an assistant professor at Arizona State University and a senior researcher at the Global Institute of Sustainability.

"This is the first time all of these approaches have been examined across various climates and geographies," Georgesce said. "We found geography matters."

Researchers found that wide deployment of cool roofs in a place like Florida could cause a metropolitan region to enjoy less rain, a potential problem when considering future water availability.

The researchers said their efforts were not intended to locate a perfect salve for the problems of climate change, but meant to show how the effectiveness of different adaptive strategies is dependent on a range of factors.





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