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The White Revolution

When I was recently transcribing the interview that Vinod Khosla did for the Milken Institute, something he said caught my attention:

Hybrids are an uneconomic way to reduce carbon dioxide. If you go to hybrids or electric cars, your cost of carbon reduction is about $100/ton. If you have 10 ways of reducing carbon at $50/ton, why would you spend $100? My beef is not with hybrids; we are investing in hybrid batteries; there is a good market and we can make money at it. But do I believe it’s going to solve the climate change problem? No. Save yourself the five grand, and instead paint your roof white. You will save more carbon that way.

He then cited this paper by Art Rosenfeld at Lawrence Berkeley Lab: “White Roofs Cool the World, Directly Offset CO2 and Delay Global Warming“.

Yesterday, speaking in London, Energy Secretary Steven Chu picked up on that theme:

Obama’s climate guru: Paint your roof white!

Speaking in London prior to a meeting of some of the world’s best minds on how to combat climate change, Dr Chu said the simple act of painting roofs white could have a dramatic impact on the amount of energy used to keep buildings comfortable, as well as directly offsetting global warming by increasing the reflectivity of the Earth.

“If that building is air-conditioned, it’s going to be a lot cooler, it can use 10 or 15 per cent less electricity,” he said. “You also do something in that you change the albedo of the Earth – you make it more reflective. So the sunlight comes down and it actually goes back up – there is no greenhouse effect,” Dr Chu said.

When sunlight is reflected off a white or light-coloured surface much of that light will pass through the atmosphere and back into space, unlike the infrared radiation emitted from the Earth’s warmed-up surface, which is blocked by greenhouse gases and causes global warming. “What we’re doing is that, as we put in more greenhouse gases, we’re putting in more insulation for infrared light. So if you make white roofs and the sunlight comes in, it goes right through that [insulation],” said Dr Chu.

The principle could also be extended to cars where white or “cool colours” designed to reflect light and radiation could make vehicles more energy efficient in summer. “If all vehicles were light-coloured, there could be considerable savings because then you can downsize the air conditioning… and downsizing the air conditioner means more efficient air conditioning and a considerable reduction in energy,” he said.

Asked about whether the US administration has any plans to manipulate the climate artificially using large-scale geoengineering programmes, Dr Chu said there were no such plans “at this time”. But painting surfaces white is one geoengineering proposal that he is taking seriously.

I have to admit that I haven’t read the paper, so I can’t comment whether there may be major flaws in the idea. It is certainly interesting, though I do wonder about the scale of painting everything white. But it would be a lot easier to paint roofs white than to go down some of the other pathways that have been floated for slowing carbon emissions. The only down side I can see is that I will have to spend more money on sunglasses. Just thinking about white roads makes my eyes hurt.


May 27, 2009 - Posted by | climate change, global warming, Steven Chu


  1. Are they incorporating the costs of painting the roofs white into their calculation? Paint has to be made and delivered to the site (also adding some non-greenhouse pollutants to the equation), workers have to commute, etc. For new construction though the impact would be less.

    Comment by armchair261 | May 27, 2009

  2. ” … there is no greenhouse effect,” Dr Chu said.”Well, yes, that quote is out of context. But it is nice all the same.And Chu’s misquote happens to be correct! A greenhouse works by interrupting convective heat transfer. Radiatively active gases like water vapor work by interrupting radiative heat transfer — an entirely different physical mechanism, with no relation to greenhouses at all.Carbon dioxide, whose presence in the atmosphere is essential for life, is a very minor radiatively active gas. But everybody knew that already, including Dr. Chu, one hopes.

    Comment by Kinuachdrach | May 27, 2009

  3. In the winter, my roof and yard are all white. maybe I could sell that as some type of carbon credit.

    Comment by Dennis Moore | May 27, 2009

  4. I happen to work in public relations for some of the most progressive “green” architecture shops in the world.There are many types of green roofs that will cool the building underneath, including earth roofs with plantings, or even traditional Spanish tile roofs, with the air gaps underneath. The cool roofs, combined with windows that let in light but not heat (called low e glass), shading, proper thermal massing, and efficient light bulbs mean that buildings can use half or less the electricity they used to. It is a remarkable testament to man’s ingenuity. Many states have adopted building energy standards (including CA), and other builders voluntarily seek LEED certification (a type of greenie stamp of approval).I expect the US could use less electricity every year, and not more, and do fine. The price signal will accomplish most of this. If electricity rates get high enough, people will use less.

    Comment by benny "reargas" cole | May 27, 2009

  5. Funny, but I picked up on the same quote. VK trashes hybrids, then admits he drives a Lexus Hybrid.Anyway, I did bother to read the paper. Not really much too it, a couple of pages with few details. Suppose that the claim is true, painting roofs white increases the reflectivity and reduces the warming effect. If painting commercial building roofs white has a significant impact, wouldn’t dark roofs on residential and commercial buildings have the opposite effect? And for that matter how about ploughing under large areas of land for agricultural purposes? Turning over the soil to plant annual crops must have some impact, as well as millions of acres of asphalt roads and parking lots. But I seem to remember global warming alarmists pooh poohing land use as a cause for warming. How can you have it both ways. If white roofs are good, manmade dark surfaces must be bad.

    Comment by KingofKaty | May 27, 2009

  6. VK trashes hybrids, then admits he drives a Lexus Hybrid.Not a flex-fuel vehicle, eh? Anyone know if the roof of his house or any of the businesses he owns is white?

    Comment by Clee | May 27, 2009

  7. I have no doubt in my mind that painting roofs white will accomplish far more than groups/sites like consumerwatchdog.com ever will!

    Comment by Russ | May 27, 2009

  8. White cars always look dirty and will need lots of water and detergent to wash. In the winter they look too much like snowbanks.Ugh say no to white cars. Plus theyre ugly.

    Comment by mike | May 27, 2009

  9. green roofs are even more ecologically sound, at least in non-drought locations, though more expensive than roof paint.(disclaimer, im an unemployed house painter, i encourage everyone to get theyre roofs white NOW!Save the enviroment!)

    Comment by mike | May 27, 2009

  10. “But I seem to remember global warming alarmists pooh poohing land use as a cause for warming.”The alarmists have long since lost any credibility — trying to hedge their bets with "climate change" when the only mechanism they have ever presented is for global warming!Back when I was doing due diligence on (alleged) Anthropogenic Global Warming, I read a number of fairly heavy tomes by scientists & engineers. Best estimate is apparently that 40% of anthropogenic CO2 has come from land use changes. Scientists also note the "missing carbon" problem — Gigatones of anthropogenic CO2 are no longer in the atmosphere; there are clearly significant mechanisms active in the biosphere that science does not properly understand.

    Comment by Kinuachdrach | May 27, 2009

  11. black solar panels on white roofs. Zebra houses everywhere.

    Comment by mike | May 27, 2009

  12. I have noticed that most of the school buses in my area have white roofs. An excellent idea if it keeps the bus cooler.I wonder what is more effective, a Prius with a white roof or a PV panel on top. My guess would be the white by a longshot. But the PV roof would give you far more green street cred.

    Comment by Dennis Moore | May 27, 2009

  13. and what about in the winter? But heating costs should increase, yes?I’m not familiar with the relative efficiencies between heating and air-conditioning, but I imagine it’d still be a net gain.

    Comment by David | May 27, 2009

  14. The architectural guidelines in our community require that roofs be of dark materials. Roof color is not a fight that I will pick with my wife.

    Comment by Fat Man | May 27, 2009

  15. Vinod may finally get something right but your best bet is to do the opposite of what he does. His cost estimates for hybrids have already been blown out of the water by the new Honda Insight, which costs roughly $5K less than the new Jetta TDI and gets a lot better mileage:www.Biodiversivist.com

    Comment by Russ Finley | May 27, 2009

  16. I’m willing to bet good money that the Jetta is faster in day to day traffic due to its immense torque curve and more pleasant to drive.Plus (in Europe) I’m also willing to bet that I could find a discounted Jetta easily enough, whereas I’d have to pay list (or damn close) for an Insight.Its curious that hybrids really aren’t all that popular in Europe, despite the expensive gas/diesel.Probably doesn’t help, that in Europe if you want a cheap car to run then there are plenty of incredibly economical (and cheap) hatchbacks to buy. There really isn’t that much of an incentive to buy a hybrid in Europe.Plus the hybrids will always feel slow compared with a strong turbo diesel. Its the mid range acceleration that has to be felt to be believed. The hybrids just can’t compete with that.Andy

    Comment by Andytk | May 27, 2009

  17. On Global Warming:It is known that a single volcanic eruption, like that of Krakatoa, can lower earth temps for a year or more.Okay, if we do indeed have a warming planet, and if indeed that is considered to be a ngative, then why not just kick up a lot of dust.Seems a lot cheaper than incredibly complicated yet ineffective (think China) regulatory and tax and cap-and-trade schemes.I just read on TOD that some nut wants to engage in massive relocations of whole populations. Really? When just setting off a Vesuvius would cool things down for a few years? Or how about sending out a few satellites with large flaps on them, to screen out the sun?Seems like there lots of cheap ways to solve global warming, if there even is global warming.

    Comment by benny "reargas" cole | May 27, 2009

  18. “dramatic impact on the amount of energy used to keep buildings comfortable”The only dramatic increase I have observed is stupid statements on energy issues from the O administration. Dr Chu that is a nice picture of Greece with the article. Notice how all the buildings are crammed together and there are no trees. It is about time that O figured out he is president of places like Ohio. I posted before about practical solutions like installing radiant barriers in attics. I did it to make my house more comfortable, not to reduce ghg. The problems with O pandering to lefty loons is that it will not provide practical energy solutions but gives the impression that there are easy solutions. If is easy we have already done it.

    Comment by Kit P | May 27, 2009

  19. “PINATUBO (1991) — Mt. Pinatubo erupted in the Philippines on June 15, 1991, and one month later Mt. Hudson in southern Chile also erupted. The Pinatubo eruption produced the largest sulfur oxide cloud this century. The combined aerosol plume of Mt. Pinatubo and Mt. Hudson diffused around the globe in a matter of months. The data collected after these eruptions show that mean world temperatures decreased by about 1 degree Centigrade over the subsequent two years. This cooling effect was welcomed by many scientists who saw it as a counter-balance to global warming.”Problem solved. Next problem.

    Comment by benny "reargas" cole | May 27, 2009

  20. From a common sense point of view, painting roofs white to save energy does make sense depending on what climate you live in. I’d imagine that in the southwest, a white (or any sort of “green” roof) could save considerable energy over the long run. In my own personal experience, the black tar roof on my apartment gets so hot you can’t walk across it in the summer.On a related note, there has been talk here in Chicago of coating the Sears Tower in a reflective aluminum coating to cut down on the a/c costs in the summer. Of course, to echo RR, anyone walking within a mile of the building will need sunglasses to see anything. And I loved my white car 🙂

    Comment by Robin | May 27, 2009

  21. Speaking of white roads, apparently Chicago is replacing some asphalt-paved alleys with water permeable high-albedo (light-colored, though not exactly white) pavement to deal with both water drainage problems and the “heat island” effect.http://www.metaefficient.com/architecture-and-building/chicago-green-alley.html

    Comment by Clee | May 27, 2009

  22. North (or south) of a certain latitude*, wouldn’t people want to paint their roofs black to absorb solar energy and help heat their homes?————-* Probably ~ 50 degrees

    Comment by Hawkshaw | May 28, 2009

  23. Hawkshaw,I am at 45 lat. and I have a black roof. A black roof doesn’t do much in the winter, because it is covered in snow most of the time. Also, the sun is at such a low angle, that the roof doesn’t get so much, but the walls and windows do.A tree does much more for you, shading the house in the summer and allowing the sun through in the winter.I would insulate first, plant trees next, and not worry about the color of my roof for anything other than esthetics. But then again I don’t have a nobel prize. I work for a company that makes roofing granules. I believe we market the green benefits of a lighter color roof. The downside of the light roof is staining and algae. But we have solved that problem with technology.

    Comment by Dennis Moore | May 29, 2009

  24. As to ‘dirty white cars’: first, only the roof and hood really need to be white, and you’d not get much muck on them — you’d just have to encourage two-tone cars. Second, people are working on engineering materials that will have darker colors still have high thermal emittance:*****Of course to sell homeowners on the concept, there’d better be more color choices than white. So that’s just what [Hasham Akbari] and his team of scientists [ at Lawrence Berkeley National Lab] are developing. … He holds up some regular composite shingles in earthy shades of green and brown, right next to their new, cool counterparts. They look identical … “because they are being engineered to have exactly the same properties in the visible part of the solar spectrum.” [Akbari says]. The key word there is “visible.” Akbari’s team has seized on the fact that only about half of the sun’s heat energy hitting your roof is in the part of the color spectrum we can see. “But if you look at the near-infrared part of the solar spectrum, you would find that the cool material is a lot more reflective than the standard one and that’s the reason that these products are significantly different. “[he says].How different? On a hot day, the engineered shingle would be 20 degrees cooler, even though they’re both the same shade of brown. These “cool” shingles are on the market, though not available everywhere.http://www.kqed.org/quest/files/download/5/radio3_urbanheatislands.pdf********

    Comment by Anonymous | May 29, 2009

  25. Dennis Moore,At high latitudes, the roof would not get much sun only if it were flat. A roof pitched at the right angle could get considerable sun ~ as long as it wasn’t overcast, and as long as it wasn’t so far north (or south) that the Sun was below the horizon for months at a time.Black roofs with water filled pipes under the roofing material could transfer considerable thermal energy into a house ~ even in the winter.My point is, that it would be possible to take advantage of black roofs as well as white roofs.

    Comment by Hawkshaw | May 29, 2009

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