White Roofs to Sweep the World, Fight Climate Change

White Roofs to Sweep the World, Fight Climate Change
by Brian Merchant, Brooklyn, New York on 05.26.09
Business & Politics
Buzz up!

It's long been known that white roofs reflect more heat back into space, reducing the amount of electricity used for A/C and thus drastically cutting down on energy consumption. Some estimates say they save billions of dollars annually. And they've just gotten their most public, most official shout out yet--Secretary of Energy Stephen Chu has recommended that the world should try to have "white roofs everywhere to help fight climate change"--remarks that were carried in hundreds of news wires around the world.

According to Bloomberg,

Painting flat roofs of homes and commercial buildings white would reflect more of the sun’s heat back to space and reduce electricity used for air conditioning by as much as 15 percent, Chu told reporters today in London, citing research by Arthur Rosenfeld, a member of the California Energy Commission.

Chu was speaking at a climate change symposium hosted by the Prince of Wales, and he called for a 'new revolution' in energy--with a number of initiatives like white roofing, stressed necessary for fighting global warming. He said that white or paler roofs would make a huge difference in scaling back energy consumption, and curbing carbon emissions. He also said that for now, he prefers solutions like white roofs to more intensive geo-engineering solutions like injecting the atmosphere with reflective particles--a suggestion that drew widespread attention and some ridicule when announced a couple weeks ago.

“Art Rosenfeld is pushing very hard for geo-engineering that we all believe will be completely benign and that is when you have a flat-roofed building, make it white,” Chu said. “It’s the equivalent of reducing the carbon emissions due to all the cars in the world by 11 years.”

It's such a simple concept that some states, like California, have already mandated commercial buildings be constructed with white roofs. But paler colors shouldn't be restricted to flat roofed commercial buildings, either:

For sloping roofs that are more visible than flat ones, Chu said paints known as “cool colors” are being developed. Those hues look like colors in the visible spectrum while reflecting a bigger portion of infra-red light, he said. Roads can also be made paler, he said.

With endorsements from such high profile figures as Chu--his remarks were carried in over 1,000 news wires--white roofs may be set for a revolution of their own.

More on White Roofs
Build a Greener Roof
How To Help Prevent Global Warming On Your Roof

Follow @TreeHugger on Twitter & get our headlines with @TH_rss!

Thirsty for more? Check out these related articles:
White Roofs to Sweep the World, Fight Climate Change
Did You Know Saving Water = Saving Electricity?
Q&A With PJM President & CEO Terry Boston
2008 US Carbon Emissions Were Lowest in 8 Years

Comments (21)
It would be nice if roof color could be changed depending on the season and latitude. After all you might not want the albedo in a cold region.
May 26, 2009 3:57 PM | flag a problem
roy says:
Wow, what a neat simple idea. I wonder why I haven't heard of this before now?
May 26, 2009 4:16 PM | flag a problem
Dallas says:
White roofs help a lot - but only in environments where cooling degree days outnumber heating degree days (ie. where it's hot and sunny). In areas like here in typically cooler, mild Seattle - you'd be better served by a black roof to help heat the home, vs. the two weeks where we actually need air conditioning.

If you use more energy/money to keep the house warm than to cool it, don't paint your roof white.
May 26, 2009 4:45 PM | flag a problem
Steve A. says:
My hero, Amory Lovins at the Rocky Mountain Institute tells of an industrial retrofit for a plant in Nevada that supplied compressed natural gas. (You cool the gas to compress it)

He saved them $68 million in 5 years by putting white sand around everything.
May 26, 2009 4:55 PM | flag a problem
Alex says:
Not being a scientist, I hope that one has tested this. If you reflect more heat back than nature would have with a natural colored roof, what does that reflected heat do to the atmosphere/ozone?

For every action there is an equal and opposite reaction. I heard that somewhere. :)

Vicki in Vegas
May 26, 2009 6:04 PM | flag a problem
Vicki Kent says:
Instead of a white roof, it would make more sense to me if they suggested planting leafy trees near your house. They'd provide shade in the summer and let the sun through in the winter. And, it costs almost nothing to plant a tree.
May 26, 2009 11:21 PM | flag a problem
Chris V says:
One day we'll look back and say "what were we thinking"?

The human species went to the moon but couldn't figure out that a white roof is beneficial?
May 27, 2009 12:15 AM | flag a problem
Nick says:
One day we'll look back and say "what were we thinking"?

The human species went to the moon but couldn't figure out that a white roof is beneficial?
May 27, 2009 12:16 AM | flag a problem
Nick says:
Where can I get some white PV panels? Mine are black.
May 27, 2009 12:35 AM | flag a problem
Jon K says:
Interesting choice of picture. Is that a private swimming pool behind every one of those eco-friendly, white-roofed buildings?
May 27, 2009 12:40 AM | flag a problem
Captain Morgan says:
The idea of Solar panels being black is to absorb the most light as possible. Electric panels are not terribly efficient and making them white would provide more reflection and less efficiency.

May 27, 2009 3:43 AM | flag a problem
animatt says:
Hasn't anyone ever been to the Greek Islands? All white buildings with a very high thermal mass and louvered shutters on all windows and doors. These buildings maintain a comfortable ambient temperature year round. Hardly a new concept, just one that we have choosen to ignore. The right shape, thermal mass, colour, etc for a certain location is not hard to work out. As usual the simple things are often the best.
May 27, 2009 5:34 AM | flag a problem
Jamie says:
There are plenty of good reasons to consider white roofs where climate-appropriate: saving money for the occupants via reduced cooling costs, using less fuel for electricity generation, and therefore reducing our reliance on foreign oil and emission of fewer REAL pollutants. However, "halting global warming" is not among them!

As serious scientists will confirm, much of the so-called science behind this theory (which enjoys only political consensus, not scientific consensus) is hastily-contrived, politically-slanted "junk science." Look at the facts objectively, people. Don't be sheep that swallow this notion unquestioningly.
May 27, 2009 8:45 AM | flag a problem
Steve Kramer says:
I live in a cool area west of Seattle. Keeping a building warm here is more of a problem and I never have any need for air conditioning. I have a problem with it getting hot for long enough that I have something new to bitch about instead of it being cool.

I do a lot of camping, just bought an old small 5th wheel camper. Going to put a lot more insulation in it and paint it a darkish green to match the environment and hide in the woods well.

And I figure that the darker color will help collect some of the suns heat and save me some propane and wood.
May 27, 2009 9:18 AM | flag a problem
Billy B says:
Jon K,

If solar panels were colored pale instead of dark blue/black, there would be no point! Solar panels need to absorb energy, and a black surface does this best!
May 27, 2009 10:49 AM | flag a problem
Ken Clive says:
I would be interested in seeing data comparing:

- white roofs to black ones
- roofs with solar panels to roofs without
- roofs with roof gardens to roofs without

And this solution, while obvious, has been around for a long time; most roofs in Baltimore, when repaired, are repaired with a high-albedo aluminum-containing paint. It gets dirty pretty quickly, but still better than black tar.

Also, look at the roof of any school bus in the country; they're pretty much all painted white at this point, for exactly the same reason.
May 27, 2009 11:51 AM | flag a problem
jwer says:
I wish I could put white on my very geometrically complicated roof here in the Colorado summers, and black in the winters--both heating and cooling costs are high. Re: trees: we have tons of trees around our house but they don't help to cool it. What about the trend towards green roofs--how would they do?
May 27, 2009 12:48 PM | flag a problem
chad henry says:
Paint your roof white regardless of its' location.
99% of homes are insulated from their roofs, thereby keeping out any solar gain whether the roof is white or not. ie a hot roof does not help heat your home. Where as, you do more good with a white roof by helping nature stay cool.
May 27, 2009 5:31 PM | flag a problem
Christopher Doyle says:
I love the comments about black roofs for winter heat. if you're further north than 50 degree the low winter sun angle probably gives no significant heating, and your roof is probably snow-covered anyway.

Yes, there are probably places where white is inefficient, I've just never lived there.
May 27, 2009 8:10 PM | flag a problem
bryan says:
"Paint your roof white regardless of its' location.
99% of homes are insulated from their roofs, thereby keeping out any solar gain whether the roof is white or not."

Not so on RV's and tents, any solar gain to them is good even if the sun is low. And where I live there is little snow in the winter and it's always above freezing during the day so even a low sun helps warm my green colored home some.
May 27, 2009 9:43 PM | flag a problem
Billy B says:
While I always try to encourage residential clients to go with the lightest color roof posssible for steep slopped roofs in warm climates, 'cool roofing' technologies on flat roofs can be problimatic. The strategy for white or 'cool roofing' for flat roofs is relatively new, so we are just starting to see the drawbacks. The high Solar Reflectance Index (SRI) has a tendency to destroy the building around it, causing unanticipated extreme joint expansion. This expansion effects mortor joints in parapet walls as well quick failure of caulkings sealants and flashing joints. These failures tend to lead to water infiltration into the building envelope causing all kinds of problems; the worst of which may be the development of toxic molds or structural failure. In the end, remediation of these problems wastes more embodied energy in labor and materials than is saved by the 'cool roof'. And, as previously mentioned in this thread, you want a dark roof if you are in a heating (cold) climate.
May 28, 2009 9:07 AM | flag a problem
Andrew Pingle, LEED AP says

I have painted both my 2-story quadriplexes white, with turquoise trim and white roofs. The energy savings were not all that significant. What HAS been significant energy-wise, is the 40-foot oak trees that shade one building and keep it 8-10 degrees cooler than the other building. Here in Miami white roofs make sense year-round as we generally only have 3-4 cool days a year to contend with.