If white roofs didn't deliver year-round energy savings, why would anyone do it? Yet that's exactly what Garry Trudeau's character Mike Doonesbury mistakenly claims.
As Mother Jones' Kiera Butler detailed last year, white roofs are a net energy win no matter where you live:
The latest white-roofs study used computer simulations to figure out what might happen if every roof in every city of the world were white. The finding: An average temperature reduction of .7 degrees Fahrenheit. Good news in general, but here’s the problem for homeowners: Since white roofs cool buildings all year round, some people have pointed out that folks with white roofs in northern climates might end up cranking the thermostat higher than their neighbors with dark-colored roofs during winter months.White roofs can save up to 20% of a building's energy costs on a hot day, as Bill Clinton recently wrote in Newsweek. The further south you go, the more in energy savings you'll see from having one - but even in Maine, you'll see a net benefit. Makes sense - not only does AC cost more than heat, but deflecting strong summer sun is a bigger benefit than absorbing much weaker winter sun.
Roofs of the future might solve this problem: Last year, a team of MIT researchers came up with a prototype of high-tech tiles that change color based on the air temperature. A cool idea for sure, but unfortunately the smart tiles aren't on the market yet. So till they are, should you spring for a white roof even if you live in the chilly north? Hashem Akbari, a senior scientist and leader of the Heat Island Group at the Lawrence Berkeley National Laboratory, says yes, since AC typically uses a lot more energy than heat. "The wintertime penalties are only a fraction of summer time savings."
And above & beyond the net energy benefit, white roofs would cut the urban heat island effect and take some of the edge off global warming. So why aren't we putting people to work painting every roof white?
To me it seems the cartoon is making a broader point - which is a sardonic assessment of how little proposed solutions can do compared to the enormity of the problem of climate change - and how complicated the tradeoffs are.
ReplyDeleteHas anyone assessed what the impact of the chemical pollution of all that paint would be?
I also want to know - does the reflected heat go all the way back to outer space or does it just bounce up to the stratosphere and get trapped there by the CO2?
I'm not a scientist and so, I'm just curious.
I also think in general, the idea of reducing heat although it might make things a bit more comfortable for some people for a while, is a serious deflection of the real problem.
For instance, it will enable people to have the impression there are solutions OTHER THAN REDUCING OUR EMISSIONS which is dangerous to say the least. Ocean acidification alone is enough to eventually destroy much of life on the planet, and when coupled with overpopulation and toxic air pollution, painting roofs seems like little more than a bandaid on a gushing wound at best, and a distraction at worst.
Thanks for posting this, it bugged me too! I have a cool roof ... in Minnesota. And I'm glad I do! In wintertime, a dark roof wouldn't do me much good, because it'd be under a few inches of snow, in any case! :)
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