Painting the City White: Over a Million Square Feet of White Roofs

Wednesday, October 13, 2010

With a soft, squishy thrust of a roller, the CoolRoofs program painted its millionth square foot of white roof on top of a housing project in the Bronx Wednesday. To celebrate the coverage, sporting an orange T-shirt just like the other volunteers, Mayor Michael Bloomberg helped roll that patch into place.

CoolRoofs is one of several programs that is painting black roofs white, and they hope it will spark a city-wide trend among building owners.

“If we can serve as a model and landlords throughout this city say 'Wait a second, if I paint my roof I'm gonna reduce my energy cost by 25 percent' next time you get your ConEd bill say 'Hey wait, maybe I should do it,'” Bloomberg said.

Building owners with white roofs need less energy for air conditioning and can save up to 50 percent on their electricity bills, according to CoolRoofs. The cost is $2 to $4 per square foot, including labor and the savings can pay for the job in as little as two years.

White roofs aren’t new. People have been white washing buildings for centuries in hot climates. Many New York roofs are already white. But now with a greater emphasis on cutting green house gas emissions white roofs have become a national cause, lead by Secretary of Energy Steven Chu.

Research has predicted that white roofs can lead to lower green house gas emissions and other environmental benefits. By painting the remaining 500 million dark roofs in New York City white, the urban heat island effect could be reduced by 33 percent; lowering temperatures by 2 degrees Fahrenheit.

CoolRoofs is a project of NYC Service, the city’s volunteer agency. Over 1,500 volunteers painted 105 roofs this summer as part of the wider effort to reduce the city’s green house gas emissions by 30 percent by 2030.

Diane Billings-Burford, chief service officer for NYC Service says next year they want to be more strategic. “Not only with our high goal of coating more rooftop, but really using the information from ConEd and the information from a wonderful team of people at Columbia [University] who are helping us to evaluate the impact this initiative really has,” Burford said. 

Next summer CoolRoofs will target neighborhoods to see if temperatures go down when the roofs go white. And energy use data will be collected from buildings with white roofs to see if electricity bills also go down.


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Comments [4]


Interesting article! Quick question - you mention 500 million roofs - I assume that must be 500 million square feet, correct?

Oct. 27 2010 01:27 PM
david from Brooklyn


You also have to keep in mind that there are two major difference between the sun in winter and summer. First, the sun is out a lot less in the winter. Second, in winter the sun stays relatively low in the sky, so even at noon it's rays are hitting the roof at an oblique angle. Because of this, the sun's ability to heat a building through the roof is much less in the winter than in summer. Which explains the findings that John from Manhattan cites.

Oct. 15 2010 07:41 AM
John from Manhattan

Not true. The "heat penalty" of a white roof has been extensively researched by the Dept of Energy's Lawrence-Berkeley National Labratory. For NYC where electricity cost $0.20 per KwH the energy savings in summer of a cool roof works out to $0.13 per sq ft while the "heat penalty" costs $0.02 per KwH. So, the annual net savings is $0.11 per sq ft. Besides, boilers are usually inefficient with antiquated steam heating that cannot be controlled by zones. How many apartments on upper floors leave the windows open in winter because there is too much heat! Talk about waste of energy.

Oct. 14 2010 10:03 PM
Rogers from Brooklyn

I am sorry, but it takes more energy to heat a home in the winter than to cool it in the summer. Paint it black if anything. A roof is naturally dark so skip the paint.

Oct. 14 2010 06:23 PM

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