White Roofs
CC photo by Sarey
David Farenthold writes in the Washington Post about the idea of painting the roofs of houses white to increase surface albedo and help counterattack the impact of climate change. My understanding of the issue is that the science behind this is perfectly sound and that we should do it. The article is prompted by remarks made by Energy Secretary Stephen Chu who’s reached the same conclusion.
This is, of course, a genre of “geoengineering” sometimes suggested by the more clever brand of right-winger as an alternative to reducing carbon emissions. It seems to me that when thinking about the entire topic, it’s useful to distinguish between “strong” and “weak” geoengineering methods. The weak ones, the kinds we should definitely do, are things like changing the color of our roofs. There’s a related issue having to do with black surface parking lots and the desirability of making them a different color and offering more tree cover. This kind of thing is, to my mind, all good and worth doing as much of as possible.
At the same time, we should be leery of “strong” geoengineering concepts that have to do with blotting out the sun or changing the structure of clouds. Those kinds of things could have extremely dangerous unintended consequences and pose all sorts of problems.
38 Responses to “White Roofs”
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June 13th, 2009 at 5:13 pm
Only works if energy saved in summer is less than extra energy consumed in winter. In other words, depends on the climate. Unless of course you re-paint the roof every winter.
June 13th, 2009 at 5:18 pm
I completely agree with Matt’s assessment, but it’s a bit incomplete. White roofs do reflect the sun radiation, reducing global warming, which is good for everyone, but very expensive to do on a high scale. But as this energy is reflected and not absorbed by the roof, it also highly reduces the roof temperature (by 50°F easily on a sunny day, IIRC), and so the cooling needs, and so the energy consumption, which is very good for the building owner, giving him an incentive to do what’s best for everyone. And as a major bonus, it also helps reduce the “heat island effect” by cutting the cooling, (which has the unintended effect to heat the outside of the building you’re cooling, leading to hot cities getting hotter).
And if you think “I live in a sunny city and I would like that, but I don’t want a white roof on my house”, scientists (disclosure: some of them in the company I work for) have developed roofs with colored paints that act almost as well as the white roofs (playing with the emissivity in the IR range). These are called “cool roofs”, look them up.
June 13th, 2009 at 5:25 pm
There is a difference between having a white roof and painting a roof white. I am not at all sure that painting existing asphalt roofs white is a good idea–if nothing else it appears to void the warranty on the roof, at least from Certainteed. Also, those little granules in the shingling come off, so you are likely to have to repaint frequently to keep it from looking nasty.
For new roofs, light-colored shingles seem like a good idea.
June 13th, 2009 at 5:47 pm
This year a journeyman golfer named Alex Cejka held a five stroke lead starting the final round of the prestigious TPC Player’s Championship.
Despite typical blazing hot and humid mid-afternoon Florida conditions, Cejka decided to tee it up dressed completely in black. Head to toe. Black hat, black shirt, black pants and belt, and black shoes. I think he even had black socks on.
Everybody knew he was smoked meat. Literally and figuratively. The poor guy was about to enter the biggest pressure cooker of his life and he decides to bake himself at same time.
Talk about a rookie mistake.
June 13th, 2009 at 6:13 pm
I’m sure this will be somewhat helpful in replacing reflective ice surfaces.
Still, it’s worth pointing out the qualitative difference between generic white surfaces and white snow and ice. One big reason we’re afraid of global warming–which is not having a tremendous impact on average temperatures yet–is its potential to melt the ice caps, raise sea levels, etc. The interaction between the greenhouse effect and the icecaps’ own reduced albedo (reduced because pollutants in the atmosphere tend to darken the surface of the ice) would cause the icecaps to absorb more heat–raising their internal temperature and causing melting. Painting rooftops would probably do little to slow that down.
It might help the microclimate in cities though; they’re pretty bad heat traps.
June 13th, 2009 at 6:48 pm
“Only works if energy saved in summer is less than extra energy consumed in winter.”
I cold climates, it doesn’t matter too much what color your roof is in the winter. It’s snow white anyway. The snow defines the color of your roof. Your point is valid for places where the snow melts. But where the snow stays around for months, it isn’t. Let’s put it this way, there are towns near me where the entrance to your house is on the second floor because the first floor is under the snow level in the winter. At that point, your roof is white regardless of what color it is.
June 13th, 2009 at 7:13 pm
To add a point about summer gains and winter losses (which is valid, climate is very important), don’t forget that during the winter, the sun is lower in the sky, and for a shorter time, than in summer. Simply put, the roof is relatively more important in summer than in winter, hence the interest to have it cooler, even if it hurts a bit during winter.
June 13th, 2009 at 7:14 pm
All in all, a sensible post. Is the strong/weak idea MY’s? If it is, that’s some good framing.
June 13th, 2009 at 7:19 pm
I agree the “weak” geoengineering Matt describes is much more appealing than “strong” geoengineering. But we should still do research on strong geoengineering as a last-ditch fallback option in case it turns out that the climate is responding catastrophically (a significant possibility) to the greenhouse gases already in the air and even a crash program to reduce emissions would not be enough.
June 13th, 2009 at 7:20 pm
…and Jeremy’s right; the “strong/weak” terminology is excellent!
June 13th, 2009 at 7:20 pm
Agreed. And the obvious follow-on question is, is carbon capture and sequestration considered geoengineering, and if so, which flavor? And how does that play into the left/right political split on the available techniques?
Not a troll question, I genuinely don’t know…
June 13th, 2009 at 7:25 pm
I’m less impressed by this post than the rest of y’all. I take global warming very seriously, and would love to see it solved by CO2 limitation. But I’m also pretty skeptical about H. sapiens’ ability to muster the political will to solve this sort of problem in advance. If it involves anyone in power making any sort of (even marginal) economic sacrifice, we’ll put it off until it starts to hurt.
So I’m not ready to stop thinking about “strong” geoengineering. We should say it’s a last resort. But we should also put a lot of effort into thinking about it. Because I’m afraid it’s a pretty likely resort.
June 13th, 2009 at 7:56 pm
This is really exciting: reducing thermal absorption by painting roofs (and perhaps other surfaces) white. What continually frustrates me is that the United States seems incapable of actually DOING some of these simple, exciting, and relatively painless things, like (my pet peeve) raising the gax tax by 10 cents.
June 13th, 2009 at 8:10 pm
“Those kinds of things could have extremely dangerous unintended consequences and pose all sorts of problems.”
I think this is true of almost all proposed solutions, isn’t it? I mean, one of the goals of the people really concerned about global warming is to basically reengineer American society from a car-centric on to something else.
I think it’s safe to say that this would be a gargantuan shift, and that we could expect to see a lot of unintended consequences.
June 13th, 2009 at 9:20 pm
@14 Sam M “one of the goals of the people really concerned about global warming is to basically reengineer American society from a car-centric on to something else.”
Certainly a laudable goal but not one that is achievable in this lifetime -baring a calamity or a catastrophic oil shock that forces Americans to return to the saddle. We are not China. We do not at present -or in any foreseeable future- have the ability, politically, to re-engineer our society in any meaningful way.
As a concerned citizen who believes climate change will reach a tipping point within two decades, I would insist the focus should be placed solely on pragmatic solutions. Time is of the essence.
First and foremost the American truck and auto fleet must be changed out, from a combustion fleet to an electric fleet. The combustion fleet is at the root of our climate change problems. Reliance on the combustion engine forces the US to import 50% of its oil, or the exact amount needed to fuel its fleet.
Imported oil is the single biggest contributor to the US deficit. If you include the minimum $2 trillion tab for our recent oil related overseas excursions, it is difficult not to conclude that oil needs are breaking us financially, making it nearly impossible to find the political will necessary to fund any meaningful climate change legislation.
Throw in the not to inconsiderable fact that 20% of total CO2 emissions in the US are released by trucks and cars, and the conclusion that the electric automobile should be of paramount importance to climate change activists is inescapable.
June 13th, 2009 at 9:20 pm
Traditional settlements in the Mediterranean already do this. Structures are whitewashed white in those beautiful posters you see of Aegean islands.
As long as we’re being natural, we could evacuate everyone for 50 miles around and use high explosives to blow up a volcano and cause it to erupt. We could use nukes, but there’s the fallout.
This sounds like a better idea than adding massive amounts of sulfur to the atmosphere, since we already know what the effect of volcanic eruptions is.
June 13th, 2009 at 9:27 pm
Matt has an excellent point here. All these strong geoengineering measures we hear about these days should be called what they are: SCIENCE GONE MAD.
June 13th, 2009 at 9:33 pm
I wonder how much it matters that you clean the roof, and repaint it often. Is paint production relatively harmless?
June 13th, 2009 at 10:08 pm
“Is paint production relatively harmless?”
No. It’s a little better than electroplating. A little less heavy metals. But when the baseline is “lot’s of Chromium” it’s not saying much. Painting roofs is silly. Next time you get a new roof, make it white. Until then, stick with the roof you have. Too bad we didn’t think of this thirty years ago. Oh yeah, we did and nobody listened. Thirty years from now, we’ll still be wondering why nobody listened. The answer is simple: we humans are monkeys whose brains got a little too big for our own good. We’re smart enough to kill ourselves, but not smart enough to save ourselves.
June 13th, 2009 at 10:18 pm
The only way this would remotely make sense is for lowering cooling costs of an individual building. It would do nothing to change the albido number of the planet in any noticeable way. Roofing material is generally made out of asphalt, or other tar material. That is naturally black. To paint over it with a white paint would require more chemicals and more energy which release carbon into the atmosphere, and would dwarf any radiative advantage in the global energy balance.
June 13th, 2009 at 10:19 pm
So I’m not ready to stop thinking about “strong” geoengineering. We should say it’s a last resort. But we should also put a lot of effort into thinking about it. Because I’m afraid it’s a pretty likely resort.
The disasters that we’ll provoke with strong-type geo-engineering, should we do something irrevocably stupid like try to create massive algae blooms or other such things will make us wish we could only get back to that global warming problem that seemed so simple.
Human beings history of actively managing any part of our environment is abysmal. The idea that we ought to do it on a global scale with enough intensity to counteract a century or more’s worth of CO2 emissions is absolutely the height of folly.
June 13th, 2009 at 10:34 pm
Geo-engineering is a bad idea, full stop.
CO2 is a well-mixed gas, so its effects are fairly uniform. The increase in water vapor and clouds that drives most of the actual global warming is far less uniform but unfortunately in currently unpredictable ways.
Climate models cannot get regional climate change. Period. They get, literally, the global warming signal right, and maybe some *very* large scale changes as well, and that’s about it. Important regional details (such as, the *sign* of the east-west temperature difference in the equatorial Pacific) are still highly controversial. To then come up with new man-made changes on the climate system that are almost all globally variable themselves is to ask the impossible of the current (and likely several future) generation of climate models, and if we cannot hope to predict what will happen it is the height of stupidity to carry out a second experiment on the global climate.
The only realistic solution is slowly down the rate of CO2 output increase to the point that carbon sequestration might begin to balance it. Spending a penny on any other geo-engineering is sheer folly.
June 14th, 2009 at 12:15 am
Speaking as someone who has actual experience with parking lots painted white, they are terrible idea. Yes, they are much cooler. However, they stay covered with ice all winter and are extremely dangerous.
June 14th, 2009 at 12:37 am
It’s probably not helpful to describe the methods you advocate as “weak” and the ones you oppose as “strong.” With various albedo-generating measures you’re talking about “low-hanging fruit,” a tired but useful metaphor because we all understand, I think, that an orchardist doesn’t meet his goals by harvesting only those.
June 14th, 2009 at 12:58 am
Also, the wingnuts were here two years ago.
June 14th, 2009 at 3:41 am
Is this a serious post? Am I missing something? I thought we moved beyond white buildings with white roofs several thousand years ago.
What is it with this micro crap. What is it with you young progressives? Your eye is completely off the ball on an issue which affects so many others. Have you learned nothing from the failed old guard? We know. Micro is tactics. Tactics are close to pointless in a national struggle. Without a macro plan, a grand strategy for this country, WE ARE COOKED.
None of these micro ideas -as fine as they are- holds the potential to jumpstart anything of true importance. The electric engine, on the other hand, dwarfs all other green ideas combined and multiplied by “pick a factor.” Only the electric automobile has the potential to drastically impact the fortunes of this Nation in the climate change arena, in the shaping a coherent Foreign Policy, and most importantly, in building a sustainable economy.
An electric car in a garage means a garage with a solar roof. A garage with a solar roof means a house covered with solar tiles. A house covered with solar tiles means 100% energy efficient skyscraping solar buildings. It is the Law of the Chain Green Reaction.
An electric auto fleet necessitates the need for a modern electric grid. The electric engine means that instead of making tiny incremental advances in the efficiency of an almost dead technology -the combustion engine, R&D people everywhere, from wind farm designers to NASCAR engine-heads, will be working to advance an untapped technology that is infinitely simpler in its operation (one moving part) and at least four times more efficient in its energy use.
Right now, as I write this, the United States has the two most advanced electric automobile companies in the world. Tesla Motors and Fisker Automotive, two California start-ups that are both ready for the big time. Both have designed and produced stylish, high powered electric sedans.
sedans.http://karma.fiskerautomotive.com/
The problem is, they are about to go to war. There will be many reasons for this pointless exercise, but mainly it will be due to a mutual pursuit of a small share of some loose stimulus funds that are lying about. It is quite possible they will kill each other in the crib -dead at birth, potential never tapped, future never realized.
What would the Chinese do in this situation? We all know what they would do. They would pull a reverse Solomon the Wise. They would demand that each company take $50 billion each. Then the Chinese government would start laying the groundwork for these companies, provide the infrastructure for their roll-out and help fund the training of the several hundred thousand workers that will needed at all the various levels.
Do you know why the Chinese bought Hummer? They are going to put an electric engine in it. What is a Hummer with a powerful electric engine? It is giant green car; a vehicle no longer facing a huge impediment on its way to a large share of the auto market…say bye, bye, gas o line.
Can you see those monstrous motherfuckers selling like hotcakes? Yes you can. We are Americans, after all.
THE FUTURE IS HUMMER! The future is being lost.
Tens of millions of jobs are stake in the race to build and perfect the electric automobile. Tens of millions. Trillions of dollars are going to be made every year. By someone. And the peoples that forge ahead in the development of the electric engine are going to simultaneously slay 40 birds with one stone. In other words, their societies are going to thrive -or dominate, if they so choose.
June 14th, 2009 at 3:57 am
I think the White roofs approach is not an alternative to reducing emissions but rather a way of reducing emissions by reducing air conditioning and electricity demand. I might be wrong, but I’d guess the direct effect of the albedo is minor — that it wouldn’t help much to paint roofs of people who don’t have air conditioners white.
I also wonder if it would be good to paint roofs in, say, Alaska black so they would need to heat less. Like the first commenter, I see a big difference between painting things white in areas where they air condition but don’t heat (or don’t heat much) like LA and in, say Chicago.
As to big geoengineering, I would favour painting Allah Akhbar in the Saudi Desert in letters big enough to be read from the moon. They have money. They have a public relations problem related to global warming. It’s already hotter than hell there. Importantly, in addition to the famous sand dune desert, they also have rocky desert where the white paint wouldn’t get covered up quickly. It would make for cool photos from satelites.
Actually maybe I’d have a better chance of convincing Khadafi as the proposal has definite appeal to a megalomaniacal exibizionist.
I think it would be just like totally Akhbar.
June 14th, 2009 at 3:58 am
I screwed up my link. Here is the Fisker site. Electric cars have come a long way.
http://karma.fiskerautomotive.com/
The Chinese are offering an $8,500 rebate to consumers for purchasing an electric automobile. We are offering something similar -9 grand?- which, if my math is correct concerning relative wealth, is peanuts compared to the Chinese.
The Tesla Model S Sedan. It is a thoroughbred. Oh, and by the way, Toshiba? I think it is, has a lithium car battery that recharges in less five minutes, and BYD, the Chinese lithium battery company turned auto maker, makes a battery acid that can be guzzled by humans. The technology has arrived.
http://www.teslamotors.com/models/index.php
June 14th, 2009 at 7:06 am
Re: However, they stay covered with ice all winter and are extremely dangerous.
Ever hear of a snow plow? If you remove the snow before it can turn to ice you don’t have a problem.
June 14th, 2009 at 7:43 am
Chu has a Nobel Prize, so I guess he has done the numbers, but I just don’t believe there is enough surface area on roofs to make much of a difference.
Any geoengineering that attempts to manipulate the earth’s albedo by affecting the amount of aerosol or particulate matter in the air is playing with fire, indeed, because the atmosphere is so complex and potentially unstable.
June 14th, 2009 at 8:09 am
further to what #23 John DE said, I thought roofs were black in order to attract heat to dissipate ice and snow; having a black roof in summer sucks for cooling, but it doesn’t cause structural problems to your roof like having a heavy wet mass resting on it. This is a good idea for places like Tucson, Vegas, Phoenix, LA, etc… but I think most roofs are light-colored there already anyway.
June 14th, 2009 at 9:27 am
Changing the color of roofing is a means to reduce energy usage, not to change the reflectivity of the planet.
June 14th, 2009 at 12:11 pm
This may be small ball, and it may be as old as Puglia, and it may have been revived in terms of this discussion by Bjorn Lomborg, but…
Small ball can help–a lot. Los Angeles and Tokyo can get up to 10-15 degrees warmer than the surrounding countryside. One of the fastest rising components of energy usage is for air conditioning. If small ball can reduce UHI in urban environments and lower air conditioning (at the right latitudes, obviously), the secondary effect is worth pursuing.
Another application of the same idea is taking the black out of blacktop. Different mixes of road coverings produce different albedos, and if you’ve ever driven in LA you’ll have seen sections of the freeway that are much lighter than others.
Of course if you really want to help the albedo of the planet, donate some really good filtering/scrubbing technology to Chinese coal plants.
June 14th, 2009 at 12:43 pm
California has just started requiring light colored roofs on commercial buildings. We put foam and a reflective white coating on the flat roof of our house two years ago and the improved comfort is spectacular. We only run the AC a few days per year now. The old tar and gravel roof allowed the house to heat up to the ambient temperature. Old houses are money pits, but old mid-century modern houses seem like they are heated and cooled with piles of burning dollar bills.
June 14th, 2009 at 1:59 pm
However, they stay covered with ice all winter and are extremely dangerous.
You do realize there are wide swaths of the country where this is not an issue.
June 14th, 2009 at 2:14 pm
Did you people read the damn article? Seriously, read it. A lot of your damn speculation is answered, or at least addressed in the article for christsakes. One, among many, example: There is also the winter problem: In a cold climate, a dark roof can lower heating costs by soaking up the winter sun. W
White-roof advocates counter that, in the continental United States, the “winter penalty” is just 10 percent of the overall savings.
“As far north as Toronto, it pays,” said Arthur H. Rosenfeld, a member of the California Energy Commission.
June 15th, 2009 at 10:04 am
It probably isn’t that difficult to incorporate a heat sensitive polymer that alters reflectivity as the roof heats. It’s possible that it might be too expensive for roofing now, but it isn’t too expensive for Coors Light cans.
June 15th, 2009 at 11:20 am
All of this balderdash will achieve nothing — not while my greatest nemesis still provides Americans with free light, heat and energy. I call this enemy…the sun. Since the beginning of time man has yearned to destroy the sun. I will do the next best thing…block it out!