Paint ’em white

In last months’ Newsweek former US president Clinton writes down a dozen ideas on how to attack the job crisis. On of his suggestions doubles as one of the most affordable weapons against climate change: painting your roof white.

There are millions of houses and buildings with tar roofs in the US, which absorb huge amounts of heat when it’s hot. Relying on the centuries-old principle that white objects absorb less heat than dark ones, white reflects the energy away from a building, helping to keep it cool. Painting black tar roofs with a white, solar-reflective coating is a low cost, quick and tangible way to save millions of dollars in energy costs and curb climate change. If you’ve got a bit more money to spend, it turns out that placing solar panels on your roof, can do the trick too; research, published recently in Solar Energy, suggests that daytime ceiling temperatures under rooftop solar photovoltaic systems are lower than under exposed rooftops. So installing solar panels on rooftops helps lessening carbon emissions, and it appears that we actually reduce energy needs at the same time.

But back to the white: studies show that white roofs reduce air-conditioning costs by 20 percent or more in hot, sunny weather. A roof covered with solar-reflective white paint reflects up to 90% of sunlight as opposed to the 20% reflected by a traditional black roof. On a 90°F day, a black roof can be up to 180°F. That heat has a major impact on interior building temperature, potentially heating your room to between 115 – 125°F. A white roof stays a cool 100°F. Plus the inside of the building stays cooler than the air outdoors, around 80°F in this example, reducing cooling costs. What is more, a white roof can cost as little as 15 percent more than its dark counterpart, depending on the materials used, while slashing electricity bills.

Clinton writes that in most of these places you could recover the cost of the paint and the labor in a week.



3 thoughts on “Paint ’em white

  1. This is just a socialist way of creating work. Actually, the increase in employment due to painting roofs white would double if the white paint is scraped off the roofs during the fall, so that the roof would absorb whatever energy is available during the cold months.
    One can in fact employ the whole population by setting half the population littering the country and the other half cleaning up. Of course, the economy will disintegrate in a week. But since it is Bill Clinton who said it, then it must be ok.

  2. In hot countries like Australia, painting roofs white, is well known as an energy reducing technique. Usually, titanium dioxide rich paint is used and the temeprature under the roof reduces dramatically. It’s just good economic sense, unless of course you like paying lots of money to the power companies or dont mind broiling during the summer heat. The technique is widely used on older, corrugated iron roofed industrial buildings, where reducing the working temperature, translates into improved productivity.

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