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Painting The World's Roofs White Could Slow Climate Change
Hugh Pickens writes "Dr. Steven Chu, the Nobel prize-winning physicist appointed by President Obama as Energy Secretary, wants to paint the world white. Chu said at the opening of the St James's Palace Nobel Laureate Symposium that by lightening paved surfaces and roofs to the color of cement, it would be possible to cut carbon emissions by as much as taking all the world's cars off the roads for 11 years. Pale surfaces reflect up to 80 percent of the sunlight that falls on them, compared with about 20 percent for dark ones, which is why roofs and walls in hot countries are often whitewashed." (Continues, below.)
"An increase in pale surfaces would help to contain climate change both by reflecting more solar radiation into space and by reducing the amount of energy needed to keep buildings cool by air-conditioning. Since 2005 California has required all flat roofs on commercial buildings to be white and Georgia and Florida give incentives to owners who install white or light-colored roofs. Put another way, boosting how much urban rooftops reflect would be a one-time carbon-offset equivalent to preventing 44 billion tons of CO2 from entering the atmosphere. 'For the first time, we're equating the value of reflective roof surfaces and CO2 reduction,' says Dr. Hashem Akbari. 'This does not make the problem of global warming go away. But we can buy ourselves some time.'"
From TFS:
that by lightening paved surfaces and roofs to the color of cement
Personally, I wouldn't want to drive on a surface that bright; I'd be squinting even with my sunglasses on!
Also, as a current resident of California, I can see the value in having a light-colored car or house, but as a former resident of New Hampshire, I can tell you that having a black car and black roof on a cold but sunny winter's day is very helpful! Snow slides off my car roof with ease, and it means I didn't have to turn the heat up quite so much!
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Believe it or not, there is a lot of research going into creating lighter colored surfaces for roads. One of the advantages is that it takes less light (and thus energy) to light up the surface at night. This also decreases the amount of "light pollution" you would have around town. There are other advantages to improving water quality and decreasing noise.
http://www.eoearth.org/article/Cool_paving
However, one of the current hangups is how to keep them light? Unless we can also change the rubber in the tires to be lighter color as well, the road surfaces just end up black again in high traffic areas like California.
That's nice for the hot countries. What about cold countries? Maybe we like having black roofs and roads to melt the snow faster if there's a little opening?
Yes. Or nearly so. I just happened to be doing some research on roof treatments. There are basically two types -- for flat roofs. Angled roofs are a different story since they're angled for snow and rain shedding. The two types of flat-roof coatings are white paint and aluminum paint.
Here's the link: http://eetd.lbl.gov/coolroof/coating.htm
White paint coatings use titanium dioxide as a pigment (very, very white) and reflect 70-80 percent of incident light. That means they keep the roof cool in the summer. They are, however, reasonably transparent to IR from below, so unfortunately do nothing to hold heat in during the winter.
Aluminum paint coatings use little flakes of alumnimum and reflect about 50-60 percent of incident light. That means they also keep the roof cool in the summer. They are, however, much less transparent to IR from below, so help keep in heat during the winter by reflecting it back down.
Then again, nothing stops you from painting your flat roof white or aluminum and unrolling black sheeting during the winter to help absorb heat from the sun.
Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
In Florida, we have only one season:
#RandomWeatherPattern
That's also why roofs are painted that way in tropical regions. No birds on the roof means you can gather a clean water supply from rainfall. Bermuda does this with excellent success.
It's a little of this, or a little of that.
I've noticed, new asphalt in the Florida summer (say 90F to 110F) roads turn into mirages, Entire cars can disappear in the at less than 1/10 mile. You can see the heat rising from them.
In older asphalt roads, where they're sun bleached and worn, the heat isn't as much of a problem.
And I've never seen it on concrete roads.
I've wondered about roads and roofs being a contributing factor to global warming. There's a lot of square miles of roofs and roads that have increased relation to the population. It's always been notable that cities are hotter than the countryside surrounding them.
I've wondered about the heat put off by internal combustion engines. We're taking massive amounts of stored energy (oils, etc) and turning them into heat and motion. How many BTU per hour does an average car put off? In passenger vehicles, even in the winter, a small fraction of that heat is redirected into the passenger compartment, and can turn it into a freakin' oven. Look at the size of the heater core versus the radiator.
In the summer, that's increased, as the load on the cooling system is added onto by running the A/C in the car (more load on the engine). The amount of heat moved from the passenger compartment to the outside should be a wash, as should the heat transfer from a building.
Serious? Seriousness is well above my pay grade.
A house built to with heat conservation in mind should almost heat itself. I've moved into a new flat building in the UK, between all the insulation and double glazing its actually hard for me to get the flat cooler than 21 degrees.
During the winter when it reached -8 degrees outside, my flat without any heating was at 16 degrees. My neighbours have the same issue, we only have the one small flat below us so the heat isn't coming from downstairs.
I can think of several other new buildings which suffer from this problem. If your going to argue about the color of a building mandating improved heat conservation should remove most of the heating costs.
Not just quick dry... All cement is an exothermic reaction. And would people SERIOUSLY stop calling concrete cement. Roads are made of concrete, which is a mixture of cement, aggregate, and water. Cement is only the binder of the mix.
Yes it's an anecdote! Were you expecting original research in a Slashdot comment?
I drive on the Autobahn every other day, and practically all of it is paved with asphalt.
Also, mean temperatures in Germany (13C) are much higher than in Canada (-8C).
If you want proof, take a look:
1) It's asphalt.
2) The beer is not frozen.