How Painting Roofs White Can Help ‘Turn Off The World For A Year’

I’m drawn to “boring” ways to change energy use: things like daylighting, reducing packaging, and making company supply-chains more efficient. Without these methods to help reduce our energy demand, the “exciting” solutions like renewable energy are less valuable.

And what could be more boring than painting a roof white? Turns out, it’s also an important solution for reducing energy use and lowering carbon dioxide emissions.

A NASA survey of New York City’s rooftops last July showed that dark, heat-absorbing rooftops were up to 42 degrees F hotter than white rooftops. And that difference in heat can make a big difference in on-site energy use; painting a roof white can reduce air conditioning demand as much as 20 percent.

In February, researchers at Concordia University estimated that painting one percent of the world’s urban surfaces white (rooftops and pavement) could reduce CO2 emissions by 130 gigatons over the next 50-100 years. In 2011, global CO2 emissions from fossil fuel combustion reached 31.5 gigatons.

Clearly, white roofs are a major opportunity. But while we’ve seen a proliferation of companies selling on-site solar and efficiency services, there’s been only modest activity in this market. Why aren’t more companies jumping on this around the country?

“I’m not sure why an organization doesn’t exist like this in every city. And it should,” says Juan Carlos, founder of the White Roof Project, a non-profit based in New York City that harnesses volunteers to provide roof painting services.

Having found a good niche with decent demand, the organization is now trying to branch out of New York and take its rooftop painting model nationwide. According to Carlos, painting 5% of the world’s rooftops white per year by 2030 could save enough emissions to equal the world’s carbon output in 2010.

“That would essentially turn off the entire world for an entire year,” he says.

The film below documents what the organization is trying to accomplish. With cities around the world adopting building codes to promote white roofs, the opportunities for this solution are increasing. But we’ve still got a long way to go before we can service so many rooftops per year.

21 Responses to How Painting Roofs White Can Help ‘Turn Off The World For A Year’

  1. Alan Frederick says:

    I have often wondered if these studies take into account the opposite situation: does the higher reflectivity of white roofs increase the amount of CO2 released by heating during the winter months?

  2. Gingerbaker says:

    If I am not mistaken, a proposed photovoltaic paint is based on the major ingredient of white pigment – titanium dioxide.


    So, one day… white paint that also generates electricity?

  3. Joan Savage says:

    I heat with gas and cool with electricity from wind power, so versions of your question come to mind often.
    I have a light grey asphalt roof that looks almost white on a sunny day. I wondered how to darken the roof in winter, but often there is a white snow cover on the roof! I settled for better insulation to reduce use of gas for heating.

    The white roof project has biggest benefit in areas with high AC demand and dependency on fossil fuel for electricity generation.
    At least a light-colored roof reduces my electricity bill in summer, even though it is from a relatively guiltless source of electricity.

  4. rjs says:

    i chose black shingles when i re-roofed in the 70s…in NE Ohio, i have 2 room A/Cs i only occasionally use, but i heat during 7 months most years, & heat oil costs me over $700/mo in mid-winter…

  5. catman306 says:

    Developers just cleared 70 acres of pines and oaks to clear land for a new mall (!) near me in Oconee, GA. But they’ve already made plans to install a white roof to keep the A/C costs down and maybe their sq.ft.rental fees. That white roof may make up for the environmental loss of cutting the trees. White roofs are definitely a good move that I’d like to see spreading across the world.

    Make it the law or, at least, provide tax incentives to those who chose white roofing or white re-roofing materials.

  6. Leif says:

    That many gigatons of energy represents a powerful amount of fossil fuel that does not have to be bought by “We the People.”
    My winter heat costs me ~$60/ month in the North West for a 1300 sq.’ home @ 48 degree latitude. I have ~20″ of ceiling insulation and a ductless heat pump.

  7. MorinMoss says:

    And perhaps also clean the air at the same time:

  8. Makan says:

    Oh the folly! The folly!

    How have we come to this, that we need NASA (NASA!) to do a study to tell us that white roofs reflect heat better than black ones and keep buildings cooler in summer?

    It’s something our grandmothers knew well enough.

  9. Rangachari Anand says:

    Who would be building a new mall in this economy, especially when there is already too much retail capacity.

  10. Arun Hegde says:

    Does this work even for very hot countries like India? Somehow think that in India ambient air at 45 degrees celsius is what contributes more to the heat load than sun falling on roofs.

  11. Lauren says:

    Companies should invest in “green roofs” rather than just painting their roof white. Green roofs act as a great insulator in the winter and deter the suns rays in the summer (best of both worlds). This will reduce the CO2 emissions emitted through energy conservation, but also absorb other CO2 molecules previously emitted. Living in NYC, runoff is also a major concern for which green roofs provide a solution.

  12. Mark Ziegler says:

    I painted my roof with the Supertherm product and now my homeowners insurance will not give me a policy because “The roof is painted”.

  13. Makan says:

    It works ESPECIALLY in hot countries like India.

  14. Makan says:

    Bummer! In NSW, Australia, dark roofs are discouraged by govt regulation.

  15. David says:

    I have been professionally coating roofs white since July 8,1980. I have documented a/c cost reductions of 39.9%. I spoke with building owners in the 1980’s in NYC and could not get any interest. There are many products, processes and, solutions that are just waiting to be embraced by the wise. White roofs are one of them.

  16. Brooks Bridges says:

    To all asking “Doesn’t a dark roof help in cold climates in winter?”

    Sunlight (daily hours and angle of sun) greatly reduced in winter compared to summer so heating effect is much lower.

    When I lived in MA and NY it also seemed like DEC and JAN were typically very cloudy.

    I don’t think Stephen Chu would be such an advocate if something this simple had been overlooked.

  17. Joel Huberman says:

    Although painting roofs white is a great idea, which should be widely implemented, it’s not like “turning off the world for a year.” Other bad effects of CO2 emissions, such as acidification of the oceans, will not be reduced by white roofs.

  18. Earl McClintock says:

    There are many factors to consider when looking for a new roof. White roofs are great down south, but not so much up north where the heating degree days far exceed the cooling days. White roof do not stay white. They quickly become dirty and not so reflective. Garden roofs are extremely expensive making them much less cost effective over the life of the roof. With added insulation the color of the roof become less of a concern. We are now talking of going to R-30 values. A cooler roof is a plus when there are roof top AC units operating there in the summer. White roofs usually don’t last as long as some of the darker roofs. White coating are a maintenance factor as they need to be recoated at least every 12-15 years. The real industry experts who know what they are taling about say the further north you go the less value there is in a white roof.

  19. Joe Romm says:

    Still, it works in most major cities in America, including most of the northern ones.

  20. wombat says:

    For those looking for the scientific tradeoff between Summer and Winter here is a very comphensive study which seems to indicate the value of the summer savings more than offsets any small value gained in winter:

  21. Beth Livensperger says:

    But coating your roof white yields an important gain for homeowners: because the white coating lowers the surface temp. of the roof by at least 50 degrees, the roof does not expand as much with the heat. Expansion and contraction due to temperature cause damage to a roof, necessitating repairs. I would also add that recoating a white roof involves rolling on two coats of paint – I don’t know what it takes to resurface a traditional flat black roof but I’m willing to bet you can’t do it yourself, and that it’s a lot more expensive.

    This site offers some good practical details:–8093#