On the radio show, Living On Earth, this morning, I heard host Bruce Gellerman interviewing Arthur Rosenberg, California's Energy Commissioner, discussing the single simplest thing any home owner can do to combat climate change. Rosenberg presented a very simple answer to the question "What Can I DO?"
Here's the Audio. From the transcript:
Painting the roof of a house white reflects solar radiation back to the atmosphere and helps cool the planet. California Energy Commissioner Arthur Rosenfeld tells host Bruce Gellerman that a white roof not only saves on air conditioning costs but, also, offsets the heating effects of ten tons of carbon dioxide emissions.There's considerably more, which I recommend heartily.
GELLERMAN: So, white roofs and roads can help cool the planet, how?
ROSENFELD: Well, everybody who's ever walked on a roof knows if it's white it will only heat up maybe ten degrees above ambient temperature. If it's some nice architectural green or terracotta tiles or whatever, it can heat up to eighty degrees above room temperature. So a white roof reflects solar radiation back into space where it's transparent, where it belongs, and a dark roof traps heat and contributes to the greenhouse effect.
GELLERMAN: We should say this is not a new idea. The ancient Greeks knew about building in light colors long, long ago.
ROSENFELD: The Greeks have known to white wash their roofs and their whole buildings for 2,000 years, and the Pharaohs had white roofs 5,000 years ago.
In Santorini, Greece houses are painted white to keep them cooler.
...
ROSENFELD: Instead of giving it to you in dollars, because I don't know your air conditioning load and your habits, I can say that it will reduce your air conditioning by 10 to 20 percent, or your air conditioning load on the summer by 10 to 20 percent if the roof is white instead of whatever you put up. White roofs are good because they save air conditioning and they're common sense. But in addition the white roof, because it doesn't trap energy, reflects it back into space, cools the world directly. And for 1,000 square feet which is like half the area of your house, a white roof as opposed to a dark roof cools the world enough to offset the heating effects of ten tons of carbon dioxide. That's like two and a half years of emissions from your family car or like one year's emissions from your house near Boston. And that's why we're so excited right now.
I"m gonna paint my roof this Spring. Key word: Elastomeric.
3 comments:
I was aware of this too...but then I am a resident of Cali.
But thanks for posting on it as I don't think its a widely known fact.
a quick explanation of why white paint works to cool the planet
1 around 50 percent of sunlight is visible light
2 around 50 percent of sunlight is heat
3 visible light is a frequency of light not absorbed by the atmosphere
4 some heat from the sun is absorbed by the atmosphere directly (greenhouse gasses which makes the atmosphere warmer).
5 heat from the sun also warms the surface of the planet and this heat is then radiated back into the atmosphere again being absorbed by greenhouse gasses.
6 visible light is poorly absorbed by the atmosphere, some of it gets reflected back by the atmosphere.
7 the visible light that doesn't get reflected back by the atmosphere is either reflected by the surface (eg a snow field) or absorbed by the surface (an asphalt carpark/ road). this absorbed light heats the dark surface. this heat is then radiated into the atmosphere and is absorbed by greenhouses gasses makiig the atmosphere warmer.
8 by painting your roof white and other surface you reflect around 50 percent of the visible energy from the sun, a significant amount of this is reflected back into space without heating the atmosphere.
9 by painting enough roofs you make buildings cooler and cool the atmosphere. air conditionig works easier to cool houses because they are cooler, perhaps you wouldn't even need air conditioning?
the main to understand is that by reflecting visible frequencies away from the planet we can cool the atmosphere.
I've heard about white roofing before, and I think it's quite effective. My aunt got her house renovated in Vancouver last summer, and her roofers suggested that they paint it white. Even bright colored umbrellas are ideal for hot weather, too. White roofs are one of the best solutions in reducing greenhouse effect.
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