2013-02-21

Co.Exist

Cool Blue Roofs May Be The Secret To Energy Savings

The color of your roof might mean a lot less money spent on cooling bills. But that color isn’t white.

As the sun beats down on buildings in the U.S., millions of dollars go up in smoke trying to cool homes and offices covered by roofs where the external temperature can reach 200 degrees. Researchers investigating the unglamorous but expensive problem are formulating answers, and new compounds, to beat the heat.

The Lawrence Berkeley National Laboratory’s Heat Island Group says a national campaign could save the nation more than $15 billion with energy savings over the 20 year lifespan of an average roof. And that’s only installing new cool roofs for new and end-of-life installations (the figure doubles for retrofitting the country’s 14,000 square miles of roofing). The best part? It’s essentially free. New "cool" coatings cost about the same (or less) than conventional materials, typically black asphalt or rubber.

Many of these new reflective colors, it turns out, are not even white. Much of the sun’s energy is emitted in the near-infrared spectrum, which is invisible to the human eye, heating up only after it is absorbed on the ground. Given the right chemical properties, even dark pigments, such as a brilliant blue invented by Oregon State University researcher Mas Subramanian, turn away much of the sun’s heat, and even provide an attractive hue for your home. Subramanian discovered his brilliant blue accidentally several years ago by cooking manganese at 2350F with a combination of yttrium and induim oxides yielding a stable, cheap and highly reflective compound. Now, car and building companies are coating their products with it to cash in on energy savings and durability, reports National Geographic.

Other new pigments and materials are likely on the way. The Department of Energy has committed (PDF) to installing roofs wherever it is practical, and U.S. Recovery and Reinvestment Act funds are flowing into basic research for new reflective pigments. The building sector is also adopting the U.S. Green Building Council’s LEED program requiring roofs reflect 29 to 78 percent of the sun’s energy (compared to 10 or 20 percent for conventional roofs).

The cost of cool should only go down as the price of new roofing materials falls and performance improves. In case you want to know how much, the Oak Ridge National Laboratory has designed a cool roof calculator to tell you exactly that.

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3 Comments

  • Poplar Network

     Actually, some more recent studies have shown that high reflectance roofs (or "cool roofs") might actually cause energy use to go up in Northern climates.  They also might actually add to climate change because they reflect solar heat back into the atmosphere, where it's trapped by pollutants.

    The jury is still out, and organizations like USGBC and the Department of Energy still recommend them, but it's an interesting discussion.  I wrote more about it here: http://www.poplarnetwork.com/n...

  • Mangal Anandan

    May be the greeks knew this all along. Google 'greece blue and white houses' and voila!

  • Emily

    Is having a cool roof installed a better investment than one would get by going solar? Obviously the cool roof is cheaper, but does the energy gained from solar offset the price difference?