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EarthTalk: The lowdown on plug-in hybrids; ecofriendly roofs

How soon can I buy a plug-in hybrid? And what are some ‘green’ choices for roofing?

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Q: I was intrigued to hear that there were a number of ways one could modify or construct a roof on a house or office that would provide great environmental benefit. Can you enlighten?
Bill Teague, Menlo Park, Calif.

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A: Most roofs are designed to shed rain and so are hard and impermeable. As a result, rainwater runs off, collecting impurities on its way to municipal storm sewers, which eventually empty into local bodies of water.

Minimizing this runoff means that more impurities will remain in local soils where they can be broken down more easily into their constituent elements than if they are concentrated downstream. In order to achieve this goal, landscape architects have developed “green roofs,” which use living plants and soil on top of a building in order to absorb, collect, and reuse rainwater while also preventing runoff.

Buildings employing green roofs find many uses for the water collected, from watering exterior plantings at ground level to flushing toilets inside.

Steven Peck, of the Toronto-based nonprofit Green Roofs for Healthy Cities, says such roofs can play a big role in maintaining ecological integrity within paved-over areas. “The roofscapes of our cities are the last urban frontier – from 15 percent to 35 percent of the total land area – and the green roof industry can turn these wasted spaces into a force for cleaner air, cleaner water, energy savings, cooling, beauty, and recreation,” he says.

The US Environmental Protection Agency (EPA) encourages the creation of green roofs to mitigate the urban “heat island effect,” whereby temperatures in crowded cities can soar some 10 degrees F. higher than in less-developed areas nearby. Such roofs also provide amenity space for tenants, reduce heating and cooling costs, scrub carbon dioxide out of the air and heavy metals out of rainwater, and increase bird habitat.

Certain inorganic materials can also make an existing roof greener. The nonprofit Cool Roof Rating Council (CRRC), for instance, suggests roofing surfaces that reflect the sun’s heat so as to reduce the urban heat-island effect while improving residential energy efficiency. According to the group, “a cool roof reflects and emits the sun’s heat back to the sky.” Builders can check out CRRC’s website for a database of information on the radiative properties of various roofing surfaces.

Long-lasting roofs, like slate or metal ones, are also more ecologically appealing, though costly.

Got an environmental question? Write: EarthTalk, c/o E – The Environmental Magazine, Box 5098, Westport, CT 06881. Or: earthtalk@emagazine.com

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