We continue our DIY series with this post re-blogged with permission from That There Paul. 

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The flat black rubber roof over my apartment would get very hot, so one sunny spring day, I painted it white

I started with a 1500-square-foot black asphalt roof.
Even at temperatures as low as 70º, the household climate would approximate Venusian conditions.

Joe Hennelly Roofing (South Boston) put a new EPDM rubber roof in, GenFlex GenSplice 10148 adhesive, $7500, great job. But still black, still hot.

I used Gaco Roof White, a silicon-based paint—do not use regular elastomeric white roof paint on a rubber roof. 20, and not 30, 1-gallon cans were plenty for 1500 square feet, two coats.  $1000.  Why not four 5-gallon buckets? Because the silicon and pigment layers separate.  Instead of trying to mix a 5-gallon bucket by hand, much easier to just pour the whole gallon into the tray.
Besides the roof paint itself, you’ll also need a pair of gloves (your hands will blister and be totally coated white otherwise), a 5-foot extension pole, a sturdy roller frame that can fit 18-inch rollers, at least 2 1½-inch roller endcaps, at least 3 18-inch ½”-nap rollers, and a 24-inch-wide rolling tray.  $114.

You can see how much sun (and heat) the whitepaint reflects away from the roof.  As any third grader could tell you, black absorbs sunlight and gets hot, while white reflects it.

By pouring a gallon a time of Gaco Roof White into the tray and rolling it on, I got the whole roof coated in 3 hours.  The next clear Sunday, I did the second coat in 2½ hours.

Four months later, the roof is holding up well.  Where water ponds, dark gray builds up, unavoidable unless you can find a way of washing the air before it rains.
With my finger, I easily wiped away a small square underneath a puddle, and saw that the Gaco Roof White underneath was intact.White roofs cool houses and may even help mitigate global warming, as explained on Wikipedia here, ThinkProgress here, DiscoveryNews here, and the New York Times here.  Incredibly, there still seems to be controversy over white roofs.  An often-viewed FastCompany article here, which, in a convoluted piece of reasoning, cites a Mark Z. Jacobsen study that “concluded that white roofs did indeed cool urban surfaces” and a Keith Oleson study that stated “white roofs would cool temperatures within buildings” to argue that “painting your roof white would be simply a massive waste,” because any reduction in global warming would be outweighed, supposedly, by more energy used to heat a building during the winter because the roof would be white.  Hello?  Isn’t that what happens anyway whenever there’s snow on the roof?  Apparently, the FastCompany article is wrong: according to a more recent 2010 Ronnen Levinson study, even up to Canadian latitudes white roofs conserve energy, helping the earth.  

The house has been awesomely cooler all summer.  Even during last month’s 100º-plus heat wave, a single air conditioner in the back bedroom cooled the entire 1250-square-foot apartment.  Oh, and you can see my house now from space. Meanwhile, the White Roof Project seeks to paint roofs white nationwide.  Rock on!

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One Response to Painted my roof white: DIY from That There Paul

  1. EPDM Rubber says:

    white roofs could prevent the emission of 24 billion metric tons of CO2, the same amount of CO2 emitted globally in 2010.
    The project says that if we covered just 5 percent of roofs with white paint per year, we’d be done by 2030. White roofs can reflect 85 percent of sunlight compare to 20 percent for black roofs and buildings with white roofs stay up to 35 degrees cooler, which means less electricity required for cooling the buildings. In large cities, white roofs also curb the heat island effect, cooling the city as a whole.

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