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Cool roofs: Basking in reflected glory
The U.S. Energy Department wants you to save green by painting your roof white -- as long as it doesn't make your neighbors see red.
Tue, Jan 19 2010 at 12:18 PM
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Go ahead. Lighten up.
The U.S. Department of Energy is encouraging the use of reflective paint and "cool roofs" to increase the energy efficiency of homes and commercial buildings. The move could reduce electric bills by 10 to 20 percent, because structures use less air conditioning when they absorb fewer of the sun's rays.
White or light-colored roofs can also cut down on what's known as the "heat island" effect that can make urban areas so dreadfully uncomfortable in the summertime. And lots of cool roofs decrease peak demand for electricity on summer afternoons, easing the strain on power plants and reducing the chances of brownouts and blackouts.
The EPA says those "islands" in cities with more than a million people can be 2 to 6 degrees warmer than surrounding areas. In the evenings, that can sometimes jump to as much as 22 degrees!
That steamy scenario adds to energy use, increases pollution and greenhouse gas emissions, and can contribute to heat-related illnesses.
Paint companies are coming up with a variety of products to help alleviate the heat.
Hyperseal products both lighten roofs and do a double dose of recycling. The primer is made from recycled rubber; the topcoat contains tiny balls of recycled glass.
"It's a great way to get rid of rubber, and it improves the quality of the paint," says Hyperseal's R.C. Autry. "It's like making paint with inner tube toughness."
Autry says he hopes the California-based company can work with the state on some large projects. It's already working with Walmart, testing a paving product that Autry says is cooler than asphalt and concrete.
The brains behind many of Hyperseal's coatings is retired Air Force Col. Ronald Savin. As a military scientist, he worked on coatings for aircraft and spacecraft. Now in his 80s, he's still whipping up prototypes with a kitchen blender.
Valspar Corp. has a solar-reflective paint for aluminum roofs, awnings and windows, and the residential market for these products is growing.
Contractors have used cool roofing products for more than 20 years. Cool roofs are installed on about 25 percent of commercial rooftops, according to the EPA, but just 10 percent of residences.
"We've had things out there since 1999 or 2000," says Valspar's Mary Ann Johnson. "But it's just now that tax credits are getting into residential markets. As energy bills go up and up, it's a good option. It decreases energy use, that also has the effect of lessening the peak energy load, reducing smog and pollution."
But before you head to the DIY store for a ginormous bucket of white paint, a few things to consider from Nadav Malin, vice president of BuildingGreen LLC and chair of the Materials and Resources Technical Advisory Group for the U.S. Green Building Council's LEED Rating System:
"Really reflective material on a pitched roof is hard to look at," Malin says. "The glare is horrible, and the neighbors are going to scream."
Light roofs are more popular in commercial buildings because offices, factories and warehouses usually have flat roofs. Bright, almost mirror-like finishes on pitched roofs in a residential area can temporarily blind drivers and permanently annoy neighborhood associations.
But when bright white is not right, there are other options.
"Because of that concern about glare, and about how a roof looks, manufacturers have invented some interesting products," Malin adds. "There are coatings and roofing materials that are reflective in the infrared spectrum, meaning they reflect heat but don't look reflective to the eye."
So a cool roof can be many different colors, if it's made from the proper materials.
The Department of Energy is now processing requests for $37 million in stimulus funding for small businesses, to develop quick-turnaround, clean-energy technologies. Improving cool roofing is on the agency's top 10 list of ways to do that.
Want more science on cool roofs? Check out this "Cool Roof Q&A" from the Lawrence Berkeley National Laboratory (PDF).
MNN homepage photo: HannahKlatt/iStockPhoto
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I wonder how good this work during the winter? What about the weight on the roof?
Easy, cheaper, solution are low your thermostat, use more blankets, just there
are little things you can do.
Portion of $1,358,600 in federal grant funding, use green roof,
Another temporary jobs, Weight on roof how good is it for it?
Is a waste of taxpayers money?
As an applicator in Southern California of Cool Roof since 1998, I can attest that bright white roofs LAST about twice as long as a dark shade of roofing material. LIFE is GOOD!
As an applicator in Southern California of Cool Roof since 1998, I can attest that bright white roofs LAST about twice as long as a dark shade of roofing material. LIFE is GOOD!
Combine high density foam and the look of clay or cement roof tile and you've got it all. INULITE roof tiles were perfect for our re-roofing project. No heat transfer into the attic and quicker installation due to being a light weight tile.
a great post which reveals the facts about Cool roofs. reflective paint and "cool roofs" to increase the energy efficiency of homes and commercial buildings. The move could reduce electric bills. Just to buy these hot reflective paint and take advantage of it.
I have a metal roof on my commercial building and had it coated last year by a contractor that used a rubber coating from Topps Products. It solved my leaky roof problem and has reduced my air conditioning bills by about 15%, which is huge here in the southern part of the country.
I hear Super Therm solves that problem by insulating the interior during cold months, while keeping heat out in hot months. I assume double duty products like this will be more common, as will "cool color" finishes and materials that don't require us to use white, but get the same or nearly the same results.
We have a home on the island of Paros in the Cyclades and all of the buildings there are painted white to reflect the heat. You can feel the difference inside a home that has a painted roof as opposed to one that does not.
I've often wondered why someone hasn't already started this trend! Between this and lighter colored roadways seem to be a no brainer to reduce our contribution to global warming!
Michelle your comments on lighter coloured roadways makes to much sense for some people. And yes it is a no brainer.
Asphalt shingles are cheap. easy to lay down. If one uses spray on foam insulation under the roof deck ICYNENE ( we did this), the attic space remains at a constant temp. This may be one of the least expensive way to keep the summer heat out and winter weather from affecting the in home temp.
Asphalt is a petroleum based product and the shingles last HALF the time of a metal, tile or concrete roof.
I heard (on NPR) of a new roof paint/material that has been invented that is a light color when it is warm, but turns dark when it is colder. This will help no matter the season. I forgot further details... sorry!
Why stay with reflective paint? Add a thin layer of soil and hardy plants and you get not just reflection but also evaporation. Green roofs also insulate during winter. They can be installed on top of traditional asphalt roofing and multiplies the life of it. Green roofs reduce the risk of flooding in urban areas since it absorbs water.
Elak, we are seeing more and more living roofs here in California and in the Seattle area. They have been common in places like Switzerland for centuries. Early settlers in the prairie states had sod roofs. Would rather look at a 'living' roof than some man made product.
Keeping the snow on a pitched roof will actually act as an insulator. Masive amounts of snow on a flat or low-pitched roof is a bad thing. But a pitched roof in good condition that was installed correctly should not be a problem.
I have a reflective metal roof. Although they are great in the summer, they are really cold in the winter. Given that cooling costs me about 35$ a month in summer, and heating would be about $200, i'd rather have some good ole asphalt shingles.
Another side effect is that if it's white (which mine isn't) the snow is just gonna pile up on there in the winter, causing other problems. So before you think about doing this, make sure you compare yours heating/cooling bills.
In the winter, the sun is much lower in the sky, less intense and there are fewer hours of daylight. The sky is usually cloudy and roofs are often covered with snow for extended periods of time. As a result, a roof is an insignificant source for heat gain during the winter, as is the heating penalty commonly associated with a cool roof. It has been proven that cool roof benefits outweigh its setbacks and save energy for even the most northern states of the U.S. (except Alaska).