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Related: About this forumBright Is The New Black: New York Roofs Go Cool (White Roof 42°F cooler than a Black Roof)
http://www.nasa.gov/topics/earth/features/ny-roofs.html[font face=Times, Times New Roman, Serif][font size=5]Bright Is The New Black: New York Roofs Go Cool[/font]
[font size=4]03.07.12[/font]
[font size=3]On the hottest day of the New York City summer in 2011, a white roof covering was measured at 42 degrees Fahrenheit cooler than the traditional black roof it was being compared to, according to a study including NASA scientists that details the first scientific results from the city's unprecedented effort to brighten rooftops and reduce its "urban heat island" effect.
The dark, sunlight-absorbing surfaces of some New York City roofs reached 170 degrees Fahrenheit on July 22, 2011, a day that set a city record for electricity usage during the peak of a heat wave. But in the largest discrepancy of that day, a white roofing material was measured at about 42 degrees cooler. The white roof being tested was a low-cost covering promoted as part of Mayor Michael Bloomberg's effort to reduce the city's greenhouse gas emissions 30 percent by 2030.
On average through the summer of 2011, the pilot white roof surface reduced peak rooftop temperature compared to a typical black roof by 43 degrees Fahrenheit, according to the study, which was the first long-term effort in New York to test how specific white roof materials held up and performed over several years.
Widespread installation of white roofs, like New York City is attempting through the NYC CoolRoofs program, could reduce city temperatures while cutting down on energy usage and resulting greenhouse gas emissions, said Stuart Gaffin, a research scientist at Columbia University, and lead author on a paper detailing the roof study. The paper published online Mar. 7, 2012, in Environmental Research Letters.
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http://dx.doi.org/10.1088/1748-9326/7/1/014029[font size=4]03.07.12[/font]
[font size=3]On the hottest day of the New York City summer in 2011, a white roof covering was measured at 42 degrees Fahrenheit cooler than the traditional black roof it was being compared to, according to a study including NASA scientists that details the first scientific results from the city's unprecedented effort to brighten rooftops and reduce its "urban heat island" effect.
The dark, sunlight-absorbing surfaces of some New York City roofs reached 170 degrees Fahrenheit on July 22, 2011, a day that set a city record for electricity usage during the peak of a heat wave. But in the largest discrepancy of that day, a white roofing material was measured at about 42 degrees cooler. The white roof being tested was a low-cost covering promoted as part of Mayor Michael Bloomberg's effort to reduce the city's greenhouse gas emissions 30 percent by 2030.
On average through the summer of 2011, the pilot white roof surface reduced peak rooftop temperature compared to a typical black roof by 43 degrees Fahrenheit, according to the study, which was the first long-term effort in New York to test how specific white roof materials held up and performed over several years.
Widespread installation of white roofs, like New York City is attempting through the NYC CoolRoofs program, could reduce city temperatures while cutting down on energy usage and resulting greenhouse gas emissions, said Stuart Gaffin, a research scientist at Columbia University, and lead author on a paper detailing the roof study. The paper published online Mar. 7, 2012, in Environmental Research Letters.
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Bright Is The New Black: New York Roofs Go Cool (White Roof 42°F cooler than a Black Roof) (Original Post)
OKIsItJustMe
Mar 2012
OP
XemaSab
(60,212 posts)1. I wonder if a white sheet or tarp would have the same effect
Black roofs for the winter; white roofs for the summer.
tech3149
(4,452 posts)2. What would be even better
A roof coating that could shift color based on ambient temperature. When temps are in the freezing range, it turns black to absorb maximum heat from the sunlight. Once the temp gets over 70 it lightens to reflect the heat.
OKIsItJustMe
(19,938 posts)3. Thermeleon
txlibdem
(6,183 posts)4. Now that is a great idea
They have windows that do that now by applying a very small electrical current they turn from clear to opaque. Perhaps the same concept could be applied to roofing materials.
PS, as I understand it, the current only needs to be applied during the change, not all the time so it's not an energy hog.
Update: they've already done it with textiles,