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White Roofs Offer a Simple Strategy to Help Combat Global Warming

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It’s amazing how the ambient temperature in a building can change so significantly through this simple action…

By Juan Carlos P.E. Posted Jul 24, 2012

Whiteroof ProjectMillions of rooftops in America are made of tar, and they absorb an enormous amount of heat during the summer months. Covering rooftops with a solar-reflective white coating reduces temperatures inside and out. White roofs are cost effective, cut carbon emissions, lower the risk of ‘brown-outs’ by reducing stress on the power grid during peak summer months, and save millions in energy costs.

Secretary of Energy Dr. Steven Chu, an advocate of white roofs, has stated that there is a potential savings of $735 million in energy costs if 85% of all air-conditioned buildings in the US had white roofs. In fact, he has mandated that all new roofs on Energy Department buildings be either white or reflective. Individual homeowners can also lower their electricity costs as much as 40% by painting their roofs white.

While the concept of converting roofs to white reflective surfaces has significant merit, putting it into practice requires some initiative. In New York, the White Roof Project, a non-profit organization, has been founded to educate and enable individuals, businesses and institutions to benefit from the energy savings of converting roofs to white, while also contributing to the reduction of carbon emissions. The White Roof Project identifies rooftops, organizes volunteers to paint them, funds community initiatives, and builds awareness in cities.

White Roof Comparison Chart

The following narrative was submitted by a team member of the White Roof Project:

It was early in the morning on one of the hottest days in NYC when we went up to paint La Mama, a historic theater on the Bowery. It’s one of many rooftops we’ve painted for the past year. We’ve been working with the Lower East Side community to find solutions to our City’s energy usage and climate change problems. Conservation efforts in this thriving neighborhood could reduce stress on our power grid more than any other neighborhood in New York State. The Lower East Side needs our help, after all, it is the heaviest energy user in the city, so our efforts there get more ‘bang for the buck’ every time a roof is coated white.

One thing that amazes me is how much the ambient temperature in a building can change so significantly through this simple action. I can say from experience that the top floors of the buildings we’ve coated are quite cool. We’ve measured the temperature inside the building on 94 degree day, and inside it was 80 degrees. We did not even need to turn the A/C on and I think that’s pretty miraculous. Compare that with the inside of a building with a black rooftop, a scorching 105 degrees.

White Roof

A New York simulation assumed a 50% adoption of cool roofs on available roof space and ran models to evaluate the temperature changes. The model predicted a city wide temperature reduction of 0.3°F.

At the end of the day we create simple, tangible change in our city by working in our community and getting our hands covered in white paint. You can be a part of the movement by coating your own roof with our easy-to-read Do It Yourself Guide. This simple step towards sustainability is comparatively cheap and easy to complete on your own. If you need help getting started, visit WhiteRoofProject.org. We’re happy to help you begin saving electricity costs and become part of the movement to help reduce global warming.
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Posted in Science and Transportation Tags , ,
  • http://www.facebook.com/rustyh Rusty Henne

    if you offset the added cost of a white roof during winter months…

  • http://twitter.com/campgearblogger Aaron Stigger

    But what about in the winter time? The black roof will absorb much needed sunlight to provide some warmth in the building.

  • http://twitter.com/roofproject White Roof Project

    There is an answer to that on the WRP website:

    http://whiteroofproject.org/research/what-about-the-winter/

  • David Leto

    The electric utility FPL pays the entire cost of white sealing businesses roofs. I is supposed to save 40% of energy costs.

  • Jim

    Wow great tip! Awesome way to reduce your home’s carbon footprint and go sustainable. I hope more cities will follow in NYC’s path and take the same initiative for white rooftops.

  • http://www.platformbedsonline.com/ Jerry LaForge

    That’s pretty interesting… but I am confused about how a white roof “reduces smog” and a black roof “keeps in smog”? Unless the graphic is suggesting that, since black roofs are hotter and people inside these buildings use more A/C, that the black roof indirectly contributes to smog… but when I first read it, it seemed to imply a “direct link” between black roofs and smog, which doesn’t make much sense to me.

  • Christa Herzog

    Wow great tip! Awesome way to reduce your home’s carbon footprint and go sustainable.

  • http://www.facebook.com/ravi.korlimarla.5 Ravi Korlimarla

    Amy Kwan had studied in detail roof-top gardening and naturally insulating homes against weather. Very interesting and thought-provoking.

  • http://www.nomadtravellers.com/ Nomad Travel

    There is also the possibility of using colored “cool paints”. They look the same at the human eye, but the spectrum is cut below the infrared, reducing the heat absorbed

  • Tracie Lavering Black

    That’s fine for flat top roofs in big cities but what about shingled houses. I’ve seen black, red, green, gray and tan shingles. I’m guessing the tan or maybe a light gray are more reflective that the other colors. Any study done on those?

    • http://eartheasy.com/ Greg Seaman

      Not that we’re aware of. But the lighter the color the more refective it will be, so your reasoning is logical.
      In a separate vein, we’ve learned that UPS is now having their brown delivery trucks made with white roofs. So even small applications have merit.

      • Bruce Millersdad

        UPS trucks have white roofs that are translucent; allowing light to transmit into the back section allowing the drivers to easily sort and collect packages for delivery simply using the sun, vs. having to put lights in the box.

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