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Green and White

If I were to post about an amazing new technology that would reduce urban heat island effects, cut ozone by 12% (thereby reducing urban smog), sequester significant amounts of atmospheric carbon, and save the residents of a large city upwards of $500 million dollars annually in energy and medical costs, I'd expect you all to be both pretty excited and fairly skeptical. Those are impressive claims. What if the new methods don't work as planned? Okay, then. How about some very old methods?

Plant trees.
Use white-colored roofing.
Use lighter-colored pavement.

In the course of some web research this morning, I stumbled across a 1997 article at the Lawrence Berkeley Labs entitled Painting the Town White -- and Green, which argues that urban heat islands (the tendency for cities to be hotter than the surrounding environment) arise not due to autos and building heat leakage, but due to the prevalence of dark, horizontal surfaces like pavement and rooftops.

We are now paying dearly for this extra heat. One sixth of the electricity consumed in the United States goes to cool buildings, at an annual power cost of $40 billion. Moreover, a 5°F heat island greatly raises the rate at which pollutants-nitrogen oxides and volatile organic compounds emanating from cars and smokestacks -"cook" into ozone, a highly oxidizing and irritating gas that is the main ingredient of smog. In Los Angeles, for example, ozone rises from an acceptable concentration at 70°F to unacceptable at 90°F. The Los Angeles heat island raises ozone levels 10-15 percent and contributes to millions of dollars in medical expenses.

The steps required to counter this heat island effect are surprisingly simple, and pay for themselves in short order. Best of all, while government support and standards can play a role in bringing about these changes, individual homeowners can take direct action leading to both private and public benefit. Cooler roofs, abundant trees, and cooler pavement each can contribute to a major reduction in urban heat, and thereby to reduced energy use, reduced ozone/smog development, and (both directly and indirectly) to reduced atmospheric carbon. And while the color and type of pavement put down is controlled by local and regional authorities, the other two methods of reducing urban heat are in individual hands.

Planting more trees is a straightforward concept, and one with a significant payoff: the LBL group estimates that 10 million added trees across the entire Los Angeles basin would reduce energy use by 900 MW, and save LA residents $273 million dollars annually -- probably more now, as the paper was written well before the power cost spikes of the early 2000s. Because shade from trees reduces the need for lawns to be watered, and the trees themselves can subsist on typical rainfall levels without needing added water, planting trees actually would reduce water demand, an increasingly critical issue in cities like LA. The LA Department of Water and Power will actually give you trees to plant in your yard for shade and energy conservation.

Cooler roofs come from changing the color of the material used for roofing shingles. Most homes have to be re-roofed about every 20 years. Changing from a dark shingle (once traditional because it was more "wood like") to a light-colored (titanium-based white or terra cotta red) shingle can cut air conditioning costs by up to 40%. Georgia has been a leader in pushing cool roofs, passing a state law encouraging the shift. A few other states and regions also provide incentives, and the federal government is considering adding heat reflectivity requirements to housing regulations.

As a homeowner who needs to put a new roof on this year, I'm particularly happy to have discovered this information!


Listed below are links to weblogs that reference Green and White:

» De la verdure sur mon toit from Le blogue d'Organigramme
Ce billet qui parle de l'impact que pourrait avoir une coloration plus claire de nos routes et de nos toits m'a remit en tête mon projet d'agriculture toituresque. Maleureusement, les coûts peuvent en être élevés, et la logistique complexe. http://w... [Read More]

» http://www.sixdifferentways.com/remainder/006700.php from Remaindered links weblog
White roofs cut air-conditioning by 40% [via]... [Read More]

» Painting white to be green from more signal - less noise
Sometimes it is the most simple things that make the biggest difference. How about painting things white to save cooling costs? Duh. Living in Texas, I know better than to buy dark summer clothes or a dark vehicle. I guess... [Read More]

» Green homes with White Roofs from dodoskido
WorldChanging: Another World Is Here: Green and White. WorldChanging reports on interesting studies that show by putting white roofs or other reflective materials on our buildings, we can make our buildings 40% cooler without having to use more energy.... [Read More]

Comments (16)


there's also green roofs :D




Out here in the Sonoran Desert roofs have been white since we've had roofs. Roofs are also more gently sloped to minimize surface area (this wouldn't work where snow loading is a concern). Only the really new houses (last ten-fifteen years) use dark shingles and abandon proven desert designs in favor of the same crap you see everywhere now.



Conversely some of us live in places where it's cold a majority of the time, so we've been doing the right thing all along with our black roofs and blacktop parking lots. :)

capitol hill:

There's a strong whiff of intellectual E. Coli in the referenced article. Fr'instance, the caption on the Wash, DC heat map asserts that the biggest hot spot (in red) is the site of the convention center.

Since the convention center (as of the article's 1997 date) was several blocks south and west of the hot spot -- i.e., south of Mass Ave, unlike the hot spot -- I'm inclined to question the reasoning and/or motives of the authors.

I suspect the big red blob is an area now referred to as NoMa (north of Mass Ave), which is rapidly transitioning these days from a treeless wasteland of parking lots to a hotbed of real estate speculation.


So for those of us who'd like a cooler white roof (and whose landlord said last year he was open to this if the cost was low) anyone have any recommendations for an appropriate paint that could be put on an existing flat tar/gravel roof? Obviously the paint needn't be particularly high quality as perfect uniformity, exact color control, and high adhesion aren't required. However not interfering with possible future roof repairs would be crucial. I did a search for something like this last year and found no sources, perhaps someone more knowledgeable will come by this posting and follow up, cc me a copy.

hoosfoos, the 1997 article addresses the issue of whether having a black roof makes sense for buildings in higher latitudes. As it turns out, even as far north as New York City, the angle of sunlight coupled with the amount of cloud cover makes a dark roof almost useless for increasing building warmth during the winter, while still having a noticeable impact during the summer. The same may not apply in places where the summers are still pretty cold...

capitol hill, not being a resident of DC, I can't argue with your assertions about what the map shows or what the state of that part of the city was in 1997. I will note, however, that the heat map shown with the article was (a) not produced by the LBL authors, and (b) used to illustrate issues in the article, but not used as evidence in or a focus for their argument. In addition, even if the hot spot is a parking lot, not a building, that doesn't refute the argument they make; also, note that the area several blocks south and west of the spot is still pretty warm.

Michael, a google search on the subject reveals several sources for cooler roof/white roof information.


Re: Available paints
I don't know what is available nationally but here in the southwest there are many speciality white roof coatings; most use a latex/rubberized base for better thermal expansion/contraction. Here is one company's site: http://www.elastek.com/



Snow Seal is a brand name selling in Washington State and can be purchased in Texas as well. It is a two coat system of latex rubberized paint. The first coat is black. The next coat is the Bright white you are asking for. The two layers provide for expansion and contraction due to weather changes. hope this helps.


for some reason, the post by capitol hill, struck me as either extremely ironic, or somehow vaguely paranoid of some kind of left wing conspiracy.

"There's a strong whiff of intellectual E. Coli in the referenced article. Fr'instance, the caption on the Wash, DC heat map asserts that the biggest hot spot (in red) is the site of the convention center.

Since the convention center (as of the article's 1997 date) was several blocks south and west of the hot spot -- i.e., south of Mass Ave, unlike the hot spot -- I'm inclined to question the reasoning and/or motives of the authors."

Was the convention center under construction during that time period? Gee, what do you think caused all the heat buildup and increased engine emissions? Possibly the huge increase of deisel fuels being burned in vast quantities by the generators and earth movers used to excavate and prepare the site. What about the cranes used to lift all those girders into place? You ever seen how fuel ineffecient some of that large machinery has to be in order to create the power to move tons of materials in the process of building something like that? So you say the "hot spot" isn't even over the site of the construction Well, that's pretty simple given that D.C. is a topographical sink hole. It was a swamp before we went and built a city on it, and one of the main features of a swamp is still, settled air. So the minor prevailing drafts that flow around the buildings of D.C. tend to concentrate the circulation of air into small pools of slow moving air pressure zones that can travel in minor variences anywhere up to half a mile. Ever sit on the river bank of the Potomac on the Virginia side along the G.W. Parkway just north of Alexandria, you can see the pockets of smog swirling on relatively "cool" March days (last I did this was in 1994, but this is an easily observable phenomenon on the Fourth of July, where large amounts of colored smoke can be observed shuffling around the roof tops near Lafaunte Plaza).

"I suspect the big red blob is an area now referred to as NoMa (north of Mass Ave), which is rapidly transitioning these days from a treeless wasteland of parking lots to a hotbed of real estate speculation."

So does that mean you are a real estate broker in the D.C. area or possibly a developer with a stake in whether they allow you to get the zoning laws changed? Besides, the government os not saying you _have_ to use a white roof on your buildings or that you _have_ to plant trees. They are quite simply stating that if you want to plant a tree, which is a valuable and useful contribution to society by harboring a natural oxygen generator. Now the last time I checked, we, as humans need O2 in our atmosphere to breath. If you feel that paving over everything in site is a "good idea" perhaps you have unwittingly revealed your plans to take over the earth, Martian Scumbag. I for one, as a representative of the human race of planet Earth shall seek out and destroy your evil plans to exteminate us from our home. We are not cockroaches. We will fight for our planet. Damned dirty apes...um, Martian apes.

The point is, a program to get people to plant more trees on thier property is part of the "good things". Like proper economic development for all citizens of this country, not just you. I think this is a valuable point. That most of those portrayed in the "corporate media" as "bad businessmen in expensive suites and limos, bleeding the company of billions while living the high life" are not the ones wishing us to realize that the real "people of influence, whose minds we need to change" are not those of the unreachable CEO's, the accountants, or lawyers, or stock brokers. No, make sure the mind of the guy down the block who has a great big hard-on for George Bush and big business. The guy who wants to be the slick lawyer with the money and the cars and the women. The career woman who thinks her job is more important than her life, be it a personal life, spiritual life, or family life. We have to know who all this "support" that the right wing talk-show hosts are talking to. Find out who is listening to this kind of malicous distortion of a valid scientific point. It's hotter in cities for a reason. Black asphalt in the summer can be used to cook on an hour after the sun sets. It retains a large amount of the heat that the sun blasts into it for nearly 10 hours or more a day in the summer. This heat does not disipate and in added to the next day, in an ever increasing cycle that causes the "killer heat waves" that the media is so fond of reporting on like a trite little blurb in the evening news hour. It's not anything trite. Those who cannot afford A/C because they are out of work, or because they work 2 jobs just to be able to afford rent and food. Why are they not entitled to a planet they can inhabit.

These are the types of arguements that we should be hearing in our society. Not an argument that some communist pinko is trying to subvert our capitolist expansionist tendencies. While it may require a little more effort, a little more planning, what harm does it cause to think about building a new structure with a light colored roof? What happened to those fantastic images of the future cities, all gleaming in the light? Why are our cities dull and grey, or annoyingly reflective with all that glaring glass. Reflecting more sunlight down onto the wonder asphalt, increasing the amount of energy absorbed and making it so in August, standing on the 42nd Street at 11PM in New York City is like standing in a house on fire, suffocating from the gasses, like carbon monoxide and carbon dioxide, 2 gasses that replace the oxygen in our bloodstream, to the point of being able to kill a person if they are asthmatic or suffering from another lung ailment that restricts the bronchial passages where oxygen is absorbed by the body into the blood stream.

These are just a few of the things that I feel are an infringement on my freedoms. The freedom to live on a planet without being confined to a building. Not having to breathe through a gas mask in a major metropolitan center. Heck, even the suburban areas of these cities are suffering from amazing problems with cast expanses of black asphalt parking lots being laid our for miles in radiating lines of development. Sure expansion is good and all, but come on, sometimes there is just too much distance between once place and the next. The fact that if you live in a suburb of D.C., you have to have a car or close access to some type of public transportation, just to get a job or go to the store. And this is such a limiting factor for so many people, they end up falling down in economic status because they can't afford to pay for living in an area close enough to employment. Or the employment decided to limit their hours because "the economy is down". Corporate profits to not measure economic growth. They measure the excess of such growth. A corporation developed from the substructure of small businesses needing to be able to supply larger and larger markets. And slowly it grows to replace those same businesses that created to demand in the market to begin with businesses. Never, in human history, has a large corporation been able to lift an economy back up from a fall. It has always been either, basically, a government bail out, where businesses are forced to pay off a loan/bail-out, or through the total collapse of the old structures and the "rising from the ashes" of other businesses. Change. We must change the minds of those who wish for the status quo. We aren't at that social utopia. We haven't created a society that is economically, socially, spirutually in balance. We can never let one side so dominate the agenda of this country to the point that careful consideration of all the aspects of a debate are explored and given a litmus test of scientific proof. And here we have a scientific proof of an observed phenomenon that proves that paving over everything is a "bad thing". Plant a tree, we might be able to mitigate this effect. Gee, was that so hard?


Chicago, oddly enough, has had a program for living roofs for a couple of years now. They've been planting gardens on top of municipal buildings as well as a street tree program, if my memory serves. Good stuff.

Evidently, this generation's Mayor Daley is mucho serious about sustainability.

Emily Gertz:

Jamais, what a coincidence: I've been reading on green roofs for the past couple weeks, thinking I might work up a WC entry about them.

Greening Rooftops for Sustainable Communities conference, June 2-4, Portland OR:

Greening Gotham plan for encouraging green roofs in New York City:
(fun Flash intro page!)

Roger Karraker:

My curiosity is piqued about the asphalt situation. The article, correctly, ignores it for individual action, because local governments call the shots.

But the article got me thinking: what are the alternatives to blacktop? Where I live (Sonoma County, northern California) asphalt is made with crushed rock and, I guess, thick crude oil. Locally, the rock is crushed blue shale, a medium shade. The oil is black. The result is black.

I recall that in some parts of Arizona I saw neat brick-colored roads. How did they do that?

More importantly, what could we do to change the color of future paving?

The "Painting the Town" article (which is linked to in the post) devotes a couple of paragraphs to pavement. They suggest several alternatives: use a lighter-color aggregate (the core material for asphalt pavement); stop the practice of "topping off" the roads with carbon-black and asphalt, which is done in part because that's how people expect roads to look; and switch to light-color Portland cement. The up-front costs of switching to cement are higher, but the roads last much longer, so it's actually cheaper in the long-run to use Portland cement instead of asphalt.


what about refrigerating the roof with ... water. The evaporation takes heat away from the surface of the roof. There's not need for a swimming pool up there, just a garden sprinkler.

Damned dirty apes...um, Martian apes.


VQP, that's an interesting idea... but one which unfortunately is ill-suited to the drought-prone parts of the country most in need of heat island abatement.


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