Sunday, February 20, 2011

Cool Roofs


The albedo of several types of roofs
Image via Wikipedia
White roofs promoted to save energy (Clarion Ledger, Sept. 17, 2010)

Also discussed here: Cool Roof Rating Council



Today’s key article describes the “cool roof” plan to reduce the energy (and emissions) used for air conditioning by reflecting sunlight, using light coloured roof surfaces. This simple method reduces as much emissions in one typical home as emitted by a car for over two years – and some American cities are making the use of cool roofs mandatory for state and municipal buildings.

Key Quotes:

“A cool roof reflects and emits the sun's heat back to the sky instead of transferring it to the building below.  "Coolness" is measured by two properties, solar reflectance and thermal emittance”

“Cool roofs are one of the quickest and lowest-cost ways we can reduce our global carbon emissions and begin the hard work of slowing climate change" (Energy Secretary Steven Chu, July 2010)

“While white roofs keep homes cool in summer by letting less heat in, they have little impact on winter heating bills, according to the Cool Roof Rating Council”

“In Arizona, cool roofs are mandatory for state and state-funded buildings”

“In New York..the Department of Buildings and other public and private groups have vowed to paint 1 million square feet of roof on city-sponsored community buildings”

“an average, 1,000-square-foot roof painted white can save 10 tons of carbon dioxide, the equivalent of emissions from one car for about 2 1/2 years. On a national scale, turning roofs cool could eliminate 2 billion tons of carbon dioxide, roughly the same as taking 20 million cars off the road for 20 years”
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