Paint it white: Cool roofs save cash and carbon

Many commercial property roofs are already close to being white, and have been so for 50 years or more. They frequently use lightly-colored gravel over tar, or asphalt shingles with embedded gravel. Thet defunitely are not black. Check out some google earth views of your nearby metro area.

The best thing is to deploy solar panels on the rooftops of 1-2 story buildings (where the rooftop absorbs most heat), and use low-e windows (mirror-like) on tall buildings (where the rooftop area is a small fraction of the building’s total surface area)

Dan in Cincinatti–Patrick is right. White is the absense of color in pigments. You combine blue, red and yellow paint and you get black. In light white is all the colors combined.

Seems to be Dan is pretty sharp… there are apparently some folks who forgot 7th grade science class ’round here.
Switch to cool sidewalks and roads and the savings rise to $2 billion annually - Right out of the story… seems like someone is advocating it by tossing in a large, but unmeasured, dollar amount to it.

Patrick in Cincinnati: Your right. I’m not a scientist. I’m an engineer. It surely, though, sounds like you’re neither. To answer your question, no I don’t go blind when I see white cars. The fact that they are a multi-surfaced object helps to diffuse the sunlight. Obviously, you’ve never been on a white membrane roof in California or Florida. I have. The surface is FLAT. Do you know what that means? The surface reflects light very well. Ever walk outside into a field of fresh snow on a sunny day. I bet you squinted at the very least.

“White is the absence of color”??? Again showing you are not a scientist nor engineer. White is actually comprised of every wavelength of light in the visible spectrum. Black is the absence of color. Out of all the actual colors, by definition (since white is all colors combined) white is the best reflector (mirrors, of course, aren’t colors, they just reflect light with near 100% efficiency.

Anyway, Patrick, I was just indicating that if we painted our roads white, like the scientists in the story advocate, the roads would be awfully bright on the days designed to reflect heat. Pay attention.

TVW in Columbus: Apparently you didn’t read the above article. They mention “The scientists calculated that a global white roofs and roads”. One can infer from what they said that they mean they want white roads (whiter than concrete?). I’m just responding to the story as written.

What is needed is a push, prod or shove, to the building industry to adapt ‘earth friendly’ building practices.

Perhaps a Government sponsored green building organization could consult with all builders on new practices to incorporate.

The planet can’t wait for the builders and paying public to adapt on their own. ANd with the downturn in the housing industry, what better time to implement.

what about some inches of soil and grass on the roof to keep the heat out in summer and inside in wintertimes?

“Where’s the environmental advantage in having car wrecks littering the highways because no one can see?
”

Dan apparently your not one of the brilliant scientists. Do you go blind when you see white cars? Probably not… actually chrome/silver reflects more (hence mirrors). White is the absence of color… and just doesn’t absorb the kind of heat other colors do… but its not the strongest reflector either.

Dan in Indiana: I don’t see the correlation between a white roof and a car wreck. No one advocated that we paint asphalt white. What’s the sense in that? Why not just switch to concrete roads? Besides the benefit in reflecting heat, the durability is greater than asphalt. Get out of your flying car and come back down to earth.

What about the additional heating costs in the winter????

Carbon credits are a joke. White roof or green (as in plant) in the south. Either black or green (as in plant) for the north. Plant covers are most ideal with many benefits known and more not recognized by MOST. HOA rules should be overridden for the sake of the enviroment. Don’t you people ever get it? You slow ss sheep need a swift kick in the ss. Again.

I see a red door and I want it painted black No colors anymore I want them to turn black …

Have any of these “brilliant” scientists who said we should have white roofs and ASPHALT been on a white roof on a sunny day? You can barely see with sunglasses ON. Where’s the environmental advantage in having car wrecks littering the highways because no one can see?

Many houses in Portugal especially in the south along the coast already have white roofs - most probably for a few hundred years. Pavements are also made from white cobbled stones (with black patterns). I believe Greece also has white roofs. I think it is time the US catches up to the rest of the world. Portugal already had the largest solar power plant, tidal power and one of the fastest growing wind farms (they own Horizon in the US). The US definitely needs to invest more in alternative fuels…not waste money in wars in oil rich countries.

i has not a idea but with making that in summer white and in winter with dark solar cell would even be more energy saving and too energy and to gicve a state support about that too would be good
f.

Owens corning makes a composite shingle in Shasta White which I have on my outbuilding and Aspen Gray, which is white and gray shades, which I have on my house.

Larry: “Wouldn’t this make you use more energy in the winter to heat your home?”
Heat loss through the roof is generally insignificant. It’s the windows that get you.

Wouldn’t this make you use more energy in the winter to heat your home? There are always trade offs.

in response to billy, white roofing products are already and have been available for a long time. They are just not popular especially for homes. White rubber membrane roofing for flat top roofs can be bought now. White rubberized paint can be applied to black roof as well. White Composite shingles are available at Home Depot and Lowes and any other Hardware store. If they don’t carry it you just have to ask. It’s easier to find in the south. So basically it won’t cost any more energy than is currently used. Consumers just need to make the choice to use the white materials. I don’t know why this is big news to anyone. White reflects light and keeps things cool. Black absorbs heat and makes things hot. I think I learned that in elementary school.

In response to Billy from Charlotte, NC, since the roofs are white they will reflect back the suns ray in the form of short wave radiation which does not contribute to global warming. It is the absorbed heat that is radiated as long wave radiation that excites CO2 and other gases in the atmosphere which causes global warming. These roofs simply mimic snow caps and glaciers which reflect the suns light, the loss of which is causing a self feeding cycle in global warming.

About 6 months ago I painted my shingled roof with a white roofing paint and the results are amazing. It used to be that after 8:30am I could not go into the attic because of the heat, but now I could literally sit in there and have a picnic at 2:00pm. I have no doubt that I’m saving big on my cooling costs.

I agree with the writter HOA’s have a lot of say in this aspect and are not going to change easily. This why I choose not to live in one.

Most of the roofs use tar based shingles. I have not heard of white tar. I am sure they can find an easier way to make cooler roofs. But till then planting more trees will have a better effect.

There is no question that white roofs are effective at reducing energy costs, particularly in cooling climates. While this approach to using reflective surfaces to save energy and reduce the heat island effect is sound, it is encountering significant resistance from the aesthetic perspective in the steep slope residential community.

Fortunately, there has been a considerable amount of research done by both the Florida Solar Energy Center and the Oak Ridge National Laboratory to show that ventilated roof systems such as concrete and clay tile are just as effective at reducing heat gain into the structure and maintain their effectiveness indefinitely whereas white roofs invariably lose their effectiveness as they age and become soiled.

In much the same manner that dual-glazed windows reduce heat loss, these ventilated systems offer a more practical alternative that still allows the building designer some freedom in color selection although light-colored roofs will still improve the performance and help reduce the heat island effect.

Where is the common sense? How much energy will be needed for 100 million homes to paint their roofs white. Someone has to make the paint, transport it, and a crew to come out and paint your roof? Won’t this extra carbon emmission offset any savings from a cool roof?

Now that everyone has a cooler house, how are we supposed to cool the atmosphere now that its been heated up with all these white roofs? No reduction in carbon emmissions will offset all this extra heat going into our atmosphere.

There are currently no manufacturers that create white asphalt shingles. Will someone please fill this need?

I live in the northeast. What about all the energy I save in the winter because I have a dark roof?

And if you coat the roof and exterior walls of the buildings with photocatalyst from a company called Green Come True, then we never have to use petroleum based cleaning products ever to keep them clean. This will significantly contribute to the global warming crisis.

If we built a big umbrella to shade the earth we could save money in the summer as well. But what about my tan??

This is another useless study that trys to justify its point by including everyone doing it. Even if it was a good idea, it is very unlikely that more than 5% would waste the time doing it. And would it cost just as much to repaint roofs and residewalk and repave roads and maintain.

The reason you see a parapit wall on roofs in most Mediterranean and tropical countries is to ward off that glare caused by white painted roofs! Just look around and you will find solutions! This idea is nothing new. Just noticed by the western scientists.

And if you add ceramic to the paint or get the ceramic already mixed at the factory the cooling effect is even higher.

Another University study years ago researched the benefits of adding attic insulation. Among other things that they found: They made a record of what color roofs the houses were and found that white roofs saved about 22% in the summer time for air conditioning savings, but cost 4% in the winter time for extra heating. So white roofs result in a good amount of energy savings.

You would have to consider the glare that white or metallic roofs would have. Perhaps one doesn’t think of this in flat areas where every building is at the same elevation, but many places are hilly, mountainous, or have taller buildings amidsts shorter buildings.

I’m looking out the window now and imagining all the currently dark-colored roofs as white. Some of the buildings are already white so I have an immediate visual comparison. Yikes, this hurts my eyes and it’s not even that sunny right now.

On another note, I used to live in a house with double-paned windows which provides a tremendous amount of extra insulation, which means both keeping the heat out when it’s hot outside and keeping the heat in when it’s cold outside. Now I live in a house with single-pane windows and the difference is very noticeable. It is a simple physics concept of transfer of heat energy through convection versus conduction.

“Green” live roofs could be more expensive and they require water, and water do not come cheap in some areas. Gray water could be used in those cases. Green cover may need some enhanced structural support, but that depends on the design of the roof garden and what type of plants are grown.

Paints are way cheaper, and using highly reflective or light colored hues would certainly help by reflecting the light back into space. Large snow covered areas have been lost forever, and those should be supplemented, and painting white on roofs is a good start.

While going to a manufactured white colored roofs and “white” pavements may _help_, the better solution would be to get back to GREEN cover.

Stones/cement convert solar energy into heat and will absorb and hold that heat, creating heat islands. This is a fact of life. Bull-dozing everything in site and paving it creates artificial heat-sinks (heat islands).

Plants convert the sunlight into plant material, oxygen, and nutrients instead of into heat.

If you want to make “green” roofs, then make GREEN roofs. If you want to reduce heat build up in the cities(reducing emissions from electic plants by reducing the need for air conditioning), then plant parks, put planters on side-walks, encourage soddies/turf roofs or even better, roof gardens.

How about painting with high gloss metallic gold or silver? The reflectivity of those are way much better than white paint, and they would look “golden” or “silvery” rich.

I agree that the best to use are solar panels, only if they become very cheap.