Brit Liggett

White Roofs Could Save U.S. (Much Needed) $735 Million per Year

by , 07/21/10

secretary of energy steven chu, white roofs, do white roofs save energy, white roofing, energy saving roofing, insulated roofing, reflective roofing, does reflective roofing save energy

Since being appointed as the Secretary of Energy, Dr. Steven Chu has been talking all about the benefits of white roofs. Now he’s going to put his own department where his mouth is by mandating that all new roofs on Energy Department buildings be either white or reflective. In his statement this week he noted the cooling effect that white roofs have on buildings — especially air-conditioned ones — as well as their ability to drastically lower energy costs – $735 million per year to be exact, if 85% of all air-conditioned buildings in the US had white roofs. With all the crises that have been going down lately, we could really use that moolah!!!

Dr. Chu has been touting white roofs for a while now. In 2009, he talked to The Daily Show’s Jon Stewart about their benefits. “When you’re thinking of putting on a new roof, make it white,” Dr. Chu said. “It costs no more to make it white than to make it black,” he added. It won’t cost any more to make your new roof white rather than the usual gray or black – and did we mention that it could save us a TON of money?

Cool roofs are one of the quickest and lowest cost ways we can reduce our global carbon emissions and begin the hard work of slowing climate change,” Dr. Chu said in a statement about his new mandate. White roofs could also drastically reduce what is known as the “heat island effect.” It is a phenomenon caused by all of the dark heat absorbing surfaces in urban areas. A study by the Lawrence Berkeley Laboratory’s Heat Island Group showed that increasing the reflectivity of road and roof surfaces in urban areas with populations over 1 million would reduce carbon dioxide emissions 1.2 gigatons of carbon dioxide annually. That’s the equivalent of taking 300 million cars of the road.

+ The Department of Energy

Via The New York Times

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38 Comments

  1. JillP December 15, 2010 at 5:42 pm

    Would have thought this would be more intuitive than it is?

  2. mdog October 30, 2010 at 6:56 pm

    At the business I work at, a new white roof was installed several years ago, replacing the old black tar roof. It really cooled down the interior of the building. It used to be that if I had to go into the unairconditioned attic which we used for storage I would be dripping from sweat within a couple of minutes, since it was twenty degrees hotter than the outside temperature. Now, even when the temperature is in triple digits, I can stand to be up there for a longer time, and the a/c doesn’t have to run all the time.

  3. soundingstorm October 14, 2010 at 7:02 pm

    It would make sense to have a roof that, when warm, lightens to white, when cold, darkens. In winter- you garner more heat. in summer- you reflect it. I know they have the ability to do something similar; i had a hotwheels car that would.

  4. Gen7's Prefab Eco Class... September 17, 2010 at 1:00 pm

    [...] Classrooms are designed for energy efficiency and feature well–insulated building envelopes, cool roofs, lots of natural light, and efficient mechanical systems. This helps the buildings exceed [...]

  5. jcpe August 18, 2010 at 8:20 pm

    I recently started a non-profit for this called the White Roof Project, and made an infographic about all the effects it would have. You can check it out here: http://bit.ly/whiteroofproject

  6. jsld August 3, 2010 at 3:58 pm

    A little much needed perspective: the US government spends roughly $170,000,000 per hour, or $735,000,000 every 4.3 hours. It is about 0.0005% of annual debt.

  7. cueball9917 August 2, 2010 at 2:01 pm

    @bill733
    I’ve lived in an area of Canada that would put temperatures of Hailey ID to shame and there were many a flat roof that did not have the benefit of edges and eaves to begin the melting process. As long as the ambient temperature is above 32F the snow will begin to melt, regardless of the color of the material underneath. Yes, a black roof will speed up that process as it begins to reveal itself, but no, a white roof is not going to automatically cause ice dams. Come on people, let’s think realistically here. FYI, you may want to check your CCD, and HDD numbers as they seem to be slightly exaggerated in your favor.

  8. bill733 July 30, 2010 at 4:44 pm

    cueball9917 I had a house in Hailey, ID with dark eves and shingles. The sun would warm the eves and edges of the roof and melt the snow back from the edges. This prevented ice dams that many of my neighbors had terrible troubles with. I don\\\’t think white roofs should be required in locations where the CDD (Cooling Degree Days) is less than 1000. (CCD for Hailey is 250 while the HDD (Heating Degree Days) is 16,500).

    Also, what\\\’s really important for a roofing material is the albedo specification. White only means that it reflects visible light well, it may not necessarily reflect well in the infra-red. A roof with a high albedo does not have to be white if it reflects infra-red well. Roofing materials should be tested for this. I\\\’d like to know what I\\\’m buying.

  9. cueball9917 July 25, 2010 at 12:53 pm

    @sethv77, Could you please explain to me how a dark roof under white snow would have any effect on the melting rate? I think your theory is somewhat flawed. As for heating costs, you may want to look into additional insulation before you blame a white roof.

  10. Gilalea024 July 24, 2010 at 10:50 pm

    The statement that white roofs would reflect heat back up at taller buildings is completely false and misinformed. White surfaces reflect LIGHT, not heat. White roofs are not hot at all, in fact–you can put your bare hand on one. Because the light is reflected, very little heat is absorbed, and therefore little if any heat is radiated. That is precisely why white roofs work so well.

  11. sethv77 July 23, 2010 at 4:51 pm

    Bad idea for anywhere that has any sort of winter/snow. The snow would not melt off a white roof nearly as well as a darker roof. My heating costs already out-weigh my cooling costs.

  12. EDMACD July 23, 2010 at 2:49 pm

    I specified a white roof be installed on my home some 10-15 years ago for the exact reasons others are finally getting around to it now. In fortunately, my contractor evidently used low quality shingles, as they have essentially turned black now and are obviously ineffective reflectors. I’m no longer comfortable climbing up there, and not sure what to use for cleaning them as well. Plus, cleaners are liable to be slippery.
    Please learn from my well-intended ignorance and try to use quality materials that resist darkening from dirt, mildew, etc. Also, nearby pine trees may have contributed to the darkening.

    I have often wondered how a double-layered roof would work. Perhaps spacers between the main, supporting roof’s structure, and a reflective, exposed one. This would mean that air could curculate between them in the manner that the old Land Rovers utilized with their double roofs… Like traveling in your own portable shade to some degree.

  13. cueball9917 July 22, 2010 at 2:55 pm

    Answer to all the winter questions.

    You roof is most likely white by nature in the winter anyway, and I totally agree with Inexpensive’s explanation as well. So the whole winter point is moot.

  14. laneman09 July 22, 2010 at 1:48 pm

    Another benefit at least for acrylic sprayed on roofs is that they save additional money because in many cases you don’t have to remove the old roof. You can simply make needed repairs and spray a base coat then a top coat over that. You can spray over metal roofs, TPO, EPDM, and even gravel, though there are some other factors in that application. If you go to http://www.conklin.com you can find out more about acrylics as well as ply systems, and membrane type systems that are very effective.

  15. Iris July 22, 2010 at 10:24 am

    Yes, a \”grass roof movement\” sounds good. We live in Oregon and have trees surrounding us. A grass roof would blend right in. We (particularly North America and Europe), have lived life for years without thought of consequence to the earth.

  16. Woody Brown July 22, 2010 at 8:19 am

    I’d like to see a grass roofs movement.

  17. justforchuckles July 22, 2010 at 2:23 am

    Point by point. There need be no additional cost. You merely choose white when getting a new roof. Two redone every year? I live in a high rise overlooking a sea of reflective, light tan,and white roofs. They are not replaced any more frequently than other roofs. Three) grey is still better than black. They do not lose their reflective ability, it diminishes as they darken. Four, The majority of America is zoned for height, ie 1 or 2 story residential, 2-4 commercial & residential, and high rises. In short not a big issue as there are a lot more short buildings than tall ones. Mid town Manhattan is one thing but when your consider all boroughs and other parts of Manhattan the building heights are fairly uniform. 5) Winter- In those cities were cold is a real consideration- The roofs are already white, ie snow. The winter sun is also weaker. It is warmer in Northern cities when it is cloudy as opposed to in clear skies.6) The real problem is simply changing behavior and aesthetic preferences.

  18. Inexpensive July 22, 2010 at 1:40 am

    1. The white color does NOT change the temperature under the roof in winter. Most buildings have insulation which is right above the drywall (or office material). That is what keeps the top floor warm, not the roof which just keeps the rain and sun rays out.

    2. Even if you don’t pick white, but something off-white, the energy savings are substantial. The difference between the lightest and darkest colors for regular house shingles is about 8 F in summer. 8 F is a big difference for your air conditioning system. If you add a 12″ insulation, you have cut your heating / cooling bill probably in half or more. And insulation is very cheap.

    3. So what if the white becomes slightly off-white/gray. Still better than black.

    4. The neighboring buildings are not heated up since most commercial roofs are flat.

    I agree with Secy Chu. White (or light color) roofs are win-win-win. There is really no negative.

  19. izmunuti July 22, 2010 at 12:54 am

    There are new roof coating products coming out soon that change to a light color when warm (in the summer) and to a dark color when cold (in the winter). I heard on NPR that MIT is developing one such coating.

  20. jpstephens July 22, 2010 at 12:23 am

    Also, what about planes….does this pose any risk to air traffic?

  21. cwazytower July 21, 2010 at 11:49 pm

    I agree with Matt.
    Rooftops represent so much wasted space in cities, we should be redesigning them to provide an array of economic, environmental and social functions, not just (but obviously including) energy efficiency. Green roofs increase energy efficiency in several ways, they reflect and provide shade from solar radiation, and retain stormwater (transpiration contributing to roof cooling). Green roofs also provide aesthetics, and opportunities to educate, decrease “nature deficit disorder”, grow food, and increase viable habitat space in urban areas. They even provide a more functionally valuable solution to insulation in the winter time (growing medium and plant debris vs. foam insulation).
    All that painting and re-painting doesn’t necessarily sound like a “green” job either. How much is leached out into the diverted stormwater these roofs undoubtedly expel into the sewers? Just sayin’

  22. Bruin36 July 21, 2010 at 11:42 pm

    White / silver roofs WORK. Yes they do dull / get dirty and lose some of their reflective power however that is only a small percentage, especially when compared to their overall savings and reflectivity. Anyone that needs proof just do a thermal scan of a black roof and a white roof the difference is remarkable – that can be backed up by temperature readings inside the top floor.

    It would also be an incredible benefit if you insulated your roof with 4-6″ of rigid insulation OUTSIDE on the top and put the new roof over that.

    Of course each building varies but the cost savings and COMFORT is noticeable and long lasting – you want to fight Al Queda then do it with insulation.

    This is proven science, in this country we build buildings inside out, if we properly air sealed them , insulated them correctly then we could reduce the cost of heating / cooling instantly by at least 60% per building. This can also be done at little to no cost over normal construction because you will downsize or eliminate some mechanical systems because you have reduced your heat / cool load.

    Once you live in a building that is properly air sealed and insulated you will never live anywhere else.

    Who says that white roofs “heat up” the surrounding taller buildings – what BULL – do you mean by reflecting the light back up and into those taller buildings windows? Thats the problem they are made of glass and I dont care what the glass U value is it is no way as good as a properly insulated wall or roof.

    We can do this and we can do this now – Germans already building passive houses on the same principle – multi family dwellings with practically NO heating or cooling plants in them.
    Insulation and reflective paint is not sexy or interesting, but if you want to get to real alternative energy then the only way to make that happen is to REDUCE your heat / cool loads so smaller solar / wind plants will then start to make economic sense

  23. caphillprof July 21, 2010 at 11:23 pm

    Yeah, this is all fine and good in June, July and August, but what about the extra heating costs of December, January and February.

    Such bozos.

  24. rbtbob July 21, 2010 at 11:01 pm

    The roof does not actually have to be white to have a high reflectance and a high emissivity. Look at coolroofs.org for the Cool Roof Rating Council website. Superior Products in Shawnee Kansas, makes a white paint called Super Therm that has both a very high reflectance and a high emissivity.

  25. MiguelSaavadera July 21, 2010 at 10:59 pm

    and could raise the atmospheric temp as much as 2.5 degrees C.

    Green grass, or parks on top of building more efficient.

  26. borisjimbo July 21, 2010 at 10:40 pm

    I told my apartment managers a couple years ago they should do this. Any alpine mountaineer would be able to tell you that white reflects a lot of energy that would otherwise heat up the surroundings.

  27. Ben Judea July 21, 2010 at 10:15 pm

    Approximate amount each city spends on street lighting in a year:
    Four examples of waste in the state of Alabama Small cities
    • Florence: $590,000 There are 3,438 street lights in Florence
    • Muscle Shoals: $372,000
    • Tuscumbia: $185,000
    • Sheffield: $207,000

    Residential areas are restricted to 100-watt bulbs. Only in high-traffic areas, do lights have a higher wattage, between 250 and 400.

    For residential streets, 175-watt mercury or 100-watt, high-pressure sodium lights are used. 400-watt, high-pressure sodium lights along major boulevards,.

    Metal Halide lamps are more efficient than their parent, the mercury vapor arc lamp. They can be as much as 50% efficient in turning electricity into light. The other 50% is given of as heat.
    I say lets get motion sensors installed on those street lights, save a ton of money. Burn less carbon fuel. Reduce light pollution. Reduce… Oh never mind it’s not worth a mouse fart.

  28. drulay July 21, 2010 at 10:03 pm

    wow $2 per citizen per year. would that even cover the cost of the paint?

  29. John Bernardo July 21, 2010 at 9:18 pm

    White roofs, typically called TPO on commercial flat roofs, have been around for more than a decade or so and do help to save energy. I will contest the statement that they don’t cost more…it depends on the long term installed cost view or the short term installation cost view. One thing I will warn you on…wear sunglasses when on a white roof or you will go snow blind! Also, they are extremely slippery when snow and ice is present…be careful around roof edges during this condition! I have been heavily involved with 150 million square feet of white roof projects per year and highly recommend them!

  30. DebMO July 21, 2010 at 9:11 pm

    That claim makes no sense. Especially for locales that have the same length winter as summer. Roof should be white in summer, dark in winter.

    Why is there still no green solution for high heat and humidity? Why is air conditioning the only solution?

  31. unique July 21, 2010 at 8:17 pm

    Many years ago I learned in public school that dark colors absorbed hear and light colors deflected heat. That is why
    we wear dark clothes in winter and light clothes in summer.
    The Government is just finding this out. Vote for me.

  32. emark148 July 21, 2010 at 8:12 pm

    Intersting finding this article today. My original (15 years) roof is currently being replaced. Going from asphalt shingle to a standing seam white metal roof. Solar reflectivity and emissivity factors of the white coated roof will reduce my electric bill as well as help the environment. This type roof certainly cost more than asphalt shingle. In addition to saving abit on the electric bill the metal roof is much more wind and rain resistant. I live in the South so there is an all year round benefit of this type of roof.

  33. arlenelmh July 21, 2010 at 7:07 pm

    I agree with postscript. I live in WI and do not have an air conditioner. My greatest energy usage is in the winter when the heater runs to keep my pipes (metal and biological) from freezing. I chose a black roof last year to lower my energy costs.

  34. MattColeridge July 21, 2010 at 1:49 pm

    There are a couple of negatives to white roofs. First of all they rapidly become grey roofs and unless they are cleaned regularly lose their reflective ability. Second, if there are neighbouring taller buildings the light reflected off the white roofs heat up the surrounding taller buildings and actually cause an increase in energy use due to greater a/c loads.

  35. gatoatigrado July 21, 2010 at 12:31 pm

    @jrussell where are you getting the numbers from? I think it is rather uninformative how they only give “total cost savings” instead of per-building, where one can easily compare it with the cost of paint and/or new roofing materials.

  36. jrussell.edu July 21, 2010 at 10:36 am

    But it would cost much more than that to do so. And it would have to be redone every other year or so because of debris. It is not cost effective enough. If only…

  37. tomdurk July 21, 2010 at 10:14 am

    I just replaced my roof, but I live in a Hysterical District & the lightest color I could get was tan–so mine is now tan. I also had a major fight w/ them over my DHHW solar panels.

  38. postscript July 21, 2010 at 9:59 am

    But what about winter?

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