Cool roofs save money, save energy, cut pollution and directly reduce warming!

What wildly underfunded climate solution can achieve all of these goals simultaneously:

  • Slow global warming by increasing the reflectivity of the Earth (geo-engineering)
  • Reduce local temperatures in the hottest cities (adaptation)
  • Reduce fossil CO2 emissions (mitigation)
  • Save U.S. consumers and businesses billions of dollars in energy costs
  • Reduce urban smog and hence cardio-pulmonary disease
  • Create more than 100,000 jobs in two years?

The answer is a major effort to make roofs (and pavements) whiter and/or more reflective, which should be coupled with a major urban tree-planting effort.

This “urban heat island mitigation” (UHIM) may well be the single most cost-effective energy and climate strategy (see background here plus “White roofs are the trillion-dollar solution“).

Now Energy Secretary Steven Chu has announced new initiatives to promote and install “cool roofs” on DOE and other federal buildings.  CAP’s Laurel Hunt has the story. 

The release of the DOE cool roofs initiatives is important step towards President Obama’s vision of greening the federal government as outlined in his Executive Order on Sustainability (E.O. 13514), which commits the federal government to reducing its greenhouse gas emissions by 28 percent by 2020.  Just yesterday, President Obama announced the expansion of the GHG emission reductions listed in E.O. 13514 by calling for an additional 13% reduction in GHG emissions from indirect sources by 2020.

Cool roofs, which improve building efficiency by reducing cooling costs and offsetting carbon emissions, will necessarily play an essential role in achieving that goal.  Cool roofs effectively reduce heat by using lighter-colored roofing surfaces or special coatings to reflect more of the sun’s heat.  A study conducted by Lawrence Berkeley National Laboratory and the Davis Energy Group found that installing a cool roof reduced the daily peak roof surface temperature of each building and could reduce energy use expended to operate cooling equipment up to 52%.

In a memo released June 1, 2010, Secretary Chu extolled the many virtues of cool roofs:

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.  By demonstrating the benefits of cool roofs on our facilities, the federal government can lead the nation toward more sustainable building practices, while reducing the federal carbon footprint and saving money for taxpayers.

Secretary Chu’s leadership on the cool roofs initiative is a critical step in reducing the nation’s greenhouse gas emissions – buildings account for 40% of U.S. energy use and about 35% of the nation’s greenhouse gas emissions.  Implementing strategies like cool roofs, roads, and pavement throughout the nation could become the equivalent of “taking every car in the world off the road for 11 years.”  Researchers also found that,

Implementing cool roofs and cool pavements in cities around the world can not only help cities stay cooler, they can also cool the world, with the potential of canceling the heating effect of up to two years of worldwide carbon dioxide emissions.

Furthermore, installing cool roofs effectively helps combat the urban heat island effect – increased warming of urban areas in comparison to rural surrounding rural areas, caused in part by the combined heat of numerous hot roofs.  Reducing the urban heat island effect will both improve air quality and lower ambient air temperature.

Specifically, Secretary Chu instructed that “all DOE offices to install cool roofs, whenever cost effective over the lifetime of the roof, when constructing new roofs or replacing old ones at DOE facilities.”  DOE also released a new resource on the roof selection process, Guidelines for Selecting Cool Roofs.  Secretary Chu also announced Monday new international cool roof opportunities to provide technical support to partnering nations, as well as a ramp up of the Roof Asset Management Program (RAMP) for roof retrofitting, which currently saves around $500,000 a year within the DOE agency that houses it; it is expected to save $10 million over the next 15 years.

Other cool roof projects are proliferating throughout the nation, too.  These range from the Donald Bren School of Environmental Science & Management, a two time LEED certified platinum building at UC Santa Barbara, to the McDonald’s Restaurant at Abercorn Common in Savannah, Georgia.  A UCSB spokesperson at UCSB states that although “greening” the building initially added to costs, “it’s safe to say the building is quickly recovering the additional costs,” saving the University money.

These projects and many others nationwide demonstrate that cool roofs are cool for the planet as well as the wallet.  Cool roofs are yet another example of a currently available, low cost technology that can make a huge economic and environmental difference now.  Even as the Senate debates a comprehensive clean energy and climate bill, which would spur further clean energy investments and energy savings, this ‘low hanging fruit’ must be aggressively harvested.

See also Get Energy Smart Now here.

26 Responses to Cool roofs save money, save energy, cut pollution and directly reduce warming!

  1. A Siegel says:

    This is tremendous … and yet ….

    Cool roofs are one of the big ‘no-brainers’ that are embraced by such rose-colored glasses wearing good-doers like Wal-Mart.

    Really have to wonder why cool roofs weren’t made policy for all USG buildings last year and basically driven into stimulus-package funding construction/renovation/repairs.

    A basic question / frustration: if the no-brainer items take 18 months (time since Secretary Chu took office), how long to get more complicated items into policy?

  2. catman306 says:

    One hundred year old farm houses and barns with metal roofs have been painted with aluminized paint for about 70 years. Our ancestors, who had lived without air conditioning until the 70s had already figured out this simple fix. That people need to be told about light colored roofs as a way to keep buildings cooler in the sun, shows how far we have slipped away from self sufficiency toward energy dependency.

    Almost all cars in Georgia were white before the age of automobile air-conditioning.

    Paint those roofs! Lighten the pavement! Easy fix!

  3. Leif says:

    Way to go Secretary Chu.
    I would only add that since we are already up on the roof it would sure be nice to put up some PV collectors as well, where appropriate.

    What do you say GOBP? Want to chip in?

    When the highways are coated perhaps a “florescence” that would absorb energy and glow softly into the night could be blended, saving street lighting. Color coded routes? Autopilots in your car? Follow a color code to your destination. Watch a movie on the way to work in a car that runs on the energy of the wind and sun.

    Just tripping there folks…

  4. Ryan T says:

    This could be especially helpful for offsetting some future emissions, unless we’ll be retrofitting a significant percentage of existing roofs in the near term. The research seems to suggest that the A/C energy savings are the main benefit, while direct planetary cooling via reflection is relatively modest (after all, cities cover a small percentage of Earth’s surface, with the oceans receiving much of the extra energy from the amplified greenhouse effect).

  5. Bob Smith says:

    Steven Chu had partially joked that if green projects weren’t very successful, then our option would be to paint EVERYTHING white!

    I’m very glad to see this cool roofs initiative coming forward, it’s a fairly simple, but important step to cut energy costs. As far as cool roads, I like the idea, however, it may be easier to use the black color to heat water, and in turn use that for something. Fortunately, so many ideas are being considered, I’m happy that we have this bag of goodies to look into.

  6. Gord says:

    We have solar panels on our roof. Actually they are on a structure that places them about 8 feet over the roof. The structure moves to compensate for the sun’s altitude in the sky.

    I guess the question is whether they would mitigate heat in a similar manner to a white roof. A large portion of the roof is in the shade for most of the day.

  7. mike roddy says:

    Yeah, this is one of the easiest and most cost effective solutions there is. If you fly over Palm Springs, you’ll see all white roofs there, since it hits 120 in summer, but plenty of places (such as Arizona) haven’t figured this out yet.

    They shouldn’t even need subsidies. This is a good niche for painting contractors if they can streamline spraying over hot mopped asphalt (the typical commercial roof coating). It’s tougher than normal painting, but of course can be done. Painters I know aren’t really marketing guys, though- commercial facilities management trade associations should be alerted.

  8. Prokaryotes says:

    Somewhat related

    Aspiring Peruvian Geoengineer Begins Project to Whitewash Andes Peaks, Hoping to Slow Glacier Melt

  9. fj2 says:

    Just wonder if white canopies are even better providing a little bit of insulation, convection, and air flow; can also be used for the sunny side of buildings.

  10. catman306 says:

    This ‘bag of goodies’ has different solutions for different locations. Geography is king. There are no magic bullet, one size fits all, solutions. There are millions of different solutions that thoughtful people can make to help fight global warming a little bit.. Because, after all, the many millions who drive every day or use electricity, each of us, is making things a little worse.

    Whitewashing the Andes is just such an idea, but grand in scale. Flipping off an unneeded light is too, but small in scale. Waste is never green. It would be good if we could restore some of the balance of nature that was here just fifty years ago. Thriftiness, thoughtfulness, willpower, and conservation move us in the right direction but don’t contribute much to the GDP. Quality vs. quantity. “What a beautiful unspoiled forest ecosystem!” vs. “Yes, it contains 1 million trees, 900 million board feet of lumber, and the real estate can be sold to developers”.

  11. Leif says:

    fj2 #9. White canopies would indeed be better except for the storm factor. Hard to keep them captured in a brisk wind.

  12. Dave says:

    I replaced my old leaky tar/composition roof with a white TPL membrane (similar to whitewater raft material) and immediately felt a dramatic reduction in summer overheating. I also seem to keep more snow on the roof in the winter, adding insulation during the heating season – no more icicles on my eaves.

    This really is a no-brainer. It would be great to see building codes require “cool” roofs. Utilities whose profits have been “decoupled” from energy sales could subsidize this to get it going. Or how about using the creative Berkeley property tax financing schemes to get new white roofs funded?

    Similarly, it is criminal that in many hot and dry climates, evaporative coolers are banned by homeowners associations because the cooler boxes appear “low class” – forcing residents to use much more energy-intensive air-conditioning. AND electric humidifiers to boot!

    We must get that low-hanging stuff, NOW.

  13. Andy says:

    Here in the Midwest, asphalt shingles are the norm (typically dark colored). Does anyone know of any product (paint or other) that could be applied over these shingles that would increase reflectivity? I would guess that application would void any manufacturers warranty, but that’s ok with me.

  14. Aubrey Enoch says:

    I have been experimenting with growing climbing vines on wire structures on several roofs to shade and cool the structure and reduce or eliminate the energy factor in a/c attributable to direct solar heat gain. I have also grown climbing vines on support structures to shade west facing windows and patio doors on a second story apartment. From what I have observed, the return on the effort has been very positive. See photos of this work at

  15. fj2 says:

    This is the New York City Cool Roofs Department of Design and Construction (DDC) manual.

  16. Prokaryotes says:

    catman306 #1 “One hundred year old farm houses and barns with metal roofs have been painted with aluminized paint for about 70 years.”

    I won’t advise the use of aluminized paint because of health and environment concerns.

    Reflective paint is a type of paint which contains thousands of little glass spheres, designed to reflect lots of light, even at night.

    Other variants of reflective paint are designed to reflect away thermal as well as optical energy. These insulators are meant to be applied to the outside of buildings in hot locations to save on air conditioning bills. Some types reflect away 44% or more of the sunlight’s energy.

  17. Erik says:

    Aluminized paint does not make a cool roof because of its low thermal emittance. I suggest that folks look at the clear and well written “Guidelines for Selecting Cool Roofs” DOE document that Joe links to above.

  18. Eric says:

    Andy, #13 – it doesn’t have to be white. I put solar-reflective asphalt shingles on my house this spring, and they look pretty normal.

    (note also solar panels) :)

    google for “Certainteed landmark solaris” for the product. Comes in many colors, and snags you a federal tax credit to boot!

  19. Jim Beacon says:

    This comment is not spam. Cool roofs are such an easy, low-cost yet highly effective part of the solution to warming that everyone should do it. To help with that end, I found out about a brush-on coating made from recycled rubber that goes well beyond the benefits of simply painting roofs white. It can be easily applied over all existing roofing coverings. It is called Hyperseal. I am in no way connected with the company but have used the product and found it does what they say. It can be applied by by DIY homeowners easily, as well as by professional painters and roofing contractors. I don’t know if links are allowed in these comments so I will simply say that a video and more detailed information can be found at

  20. GFW says:

    Andy, I’m going to read Jim’s link, but I’ll first mention that I used a white acrylic roofing paint/patch material from Gacco to cover part of my roof. That stuff sticks to everything, so while I used it on the part of my roof that *isn’t* shingled, I tested a bit of it on the shingles (asphalt or composite, not sure) and I’m sure it would have worked. It is not cheap, at $60/gallon. OTOH, that’s cheap compared to a lot of other mitigation options.

  21. GFW says:

    Yeah, I’d say the stuff I used looked nearly identical to the hyperseal primer at Jim’s link. But his is less expensive :-)

  22. Chris says:

    What if you are already using a galvanized roof? Would you still paint it with reflective paint?

  23. Raul M. says:

    I think most directions read to wash the roof with a
    mild bleach solution first before roll-on of paint.

  24. TB says:

    Wasn’t Bjorn Lomborg heavily criticised for suggesting this in his “Cool It” book?