6 ms·

US Energy Secretary: paint roofs white to fight global warming

11 points by daviday 17y ago

MichaelApproved 17y ago
This simple solution was suggested long ago. It'll help keep the building cooler and the roof will last longer. I'm so bored with these dead simple suggestions and no action.
- mahmud 17y ago
  They also suggested American school kids hide under their desks in case of a nuclear attack by the USSR! Some "solutions" are more of a psychological crutch, or placebo, than anything.
  - steveplace 17y ago
    How is this solution a psychological crutch? If there is evidence that painting roofs white will help cool off cities and reduce your a/c usage by 15%, why not do it? The analogy you provided is not applicable.
    - ars 17y ago
      "If there is evidence that painting roofs white will help cool off cities and reduce your a/c usage by 15%, why not do it?" Is there actually evidence for this? In the real world, not just some calculations? Various people have pointed out flaws such as: it won't stay white. In the winter it makes things worse, and depending on where you live the net is no good. One reason not to do it is that it costs more than it saves. And in the places where it's really bad, like Tuscon, they put white rocks on the roof, so I bet that anyplace where it's worth it - it's already being done!
      - steveplace 17y ago
        Well there's a nice video out there from our most favorite cuddly energy analyst Amory Lovins; he's talking about parking lots but the same premise holds (I think): http://fora.tv/2009/05/01/Amory_B_Lovins_Big_Savings_Through_Integrative_Design#Amory_Lovins_on_Integrative_Energy_Solutions http://fora.tv/2009/05/01/Amory_B_Lovins_Big_Savings_Through... The entire video is fascinating if you've got 2c of coffee in you.
8plot 17y ago
Someone correct me if I'm wrong, but isn't there more energy used to heat buildings than cool them? Of course it depends on many factors, including location; so a blanket statement of "white roofs everywhere" seems wrong.
- ars 17y ago
  It strongly depends on where you live. But very little of the heat from the roof gets in the building in the winter. Mainly because it's insulated. But also because hot air rises, so little of it travels down to the building space. But A/C is with vents, AKA air currents, so may be more effective at capturing heat from ceilings. But all that ignores the fact that white paint does not survive. In Tuscon the roofs would have white rocks on the roof. I strongly doubt you could make a white roof paint that would survive for more than a few years. How about shiny aluminium roofs? As a side note, I always wondered why metal roofs are not more popular. Aluminium would last pretty much forever, and it doesn't have to be one piece - you can make it into shingles for easy installation.
  - jnorthrop 17y ago
    "As a side note, I always wondered why metal roofs are not more popular. Aluminium would last pretty much forever, and it doesn't have to be one piece - you can make it into shingles for easy installation." When I re-shingled my roof a couple of years back I looked into metal roofing. The cost was almost double asphalt roofing shingles. Although a metal roof would last longer (25 years vs. 50 years), but if you wanted durability and cost wasn't an object slate roofs are expected to last 75 years or more (at least here in Maine). Of course a white roof here is useless -- I don't even own air conditioners.
  - dan_the_welder 17y ago
    As far as shiny aluminum goes, it's my experience that it does not remain shiny for long. A coating that kept it shiny would increase cost as well as the process of making it mirror finished in the first place. Once the coating failed there would be no practical way to re-polish and recoat to anywhere near factory quality and there goes your efficiency. In Florida a dull aluminum surface will be much hotter than a white painted one. Metal roofs are not as popular as they should be because the capitol cost is more and they are often considered low class. These days there are several fancy metal roofing systems that are more popular than 5 V crimp and the classic corrugated. I personally like the classic standing seam style which I saw a lot of in Maine and New Hampshire and are installed by skilled craftspeople. Asphalt shingles are made from the cheap and plentiful byproducts of the oil refining process and crushed rock. They are made from dirt and installed by low skilled labor.
TriinT 17y ago
How much energy would be spent on the production of white paint? How much energy would be saved by painting the roofs white? Unless a detailed quantitative analysis is provided, this is pretty much nonsensical...
- ars 17y ago
  The article suggests up to 15%. Assume 10%, and a $1000 yearly A/C bill, that's a savings of $100 a year. Energy spent is pretty much exactly equal to the price of the paint. So how much does paint cost? How much to install, and how long does it last? All theoretical questions, since I don't think paint that can survive on a roof exists. I'm going to make some wild guesses: You need 10 gallons of paint at a cost of $40 per gallon. And it takes about 1 day to install, at a cost of 8 hour*40 $/hour. So total it would be about $720 to install. And I bet it would last 3 to 5 years. Lets be generous and say 5. So it costs $144 per year, but saves you $100. Not a good plan. It uses more energy than it saves. Of course my numbers are totally guesses. Especially the cost for paint that does not exist.
  - TriinT 17y ago
    I like your back-of-the-envelope calculations... The problem with such seemingly unorthodox proposals is that they can be either brilliant or totally retarded. The devil is in the details. Unfortunately, neither the media nor the masses care a fig about details...
  - yardie 17y ago
    They have paints that are good for 5-10 years. They are white and you'll find them on the bottom of your local swimming pool. It's exposed to the sun everyday with the weight of hundreds of gallons of water on top of it. The paint does exist, but depending on your location you might not be able to find it. I'm sure you can get it if your along the south coast. And it doesn't necessarily have to be paint. Tiles are also useful and they are good for 20 years or more. Almost all new houses I've seen built in Florida for the last 15 years have been using white tiles for the roof.
    - 17y ago
delano 17y ago
I'm not an expert on the matter, but my understanding is that rooftop greenery is a cheaper and more effective way to reduce cooling in the summer and heating in the winter.
- Gupie 17y ago
  Perhaps however white roofs or roads etc would increase the amount of heat reflected back into space, as per the shrinking ice caps.
  - olefoo 17y ago
    Even if we made every roof and every road a pure titanium white, it wouldn't make up for more than a fraction of the albedo change caused by the shrinking of the ice caps. In the US roads cover less than 3% of the surface and all artificial structures together cover less than 10% of the surface.
    - yummyfajitas 17y ago
      The relevant quantity is not albedo x area. The relevant quantity is energy reflected = albedo x area x energy deposition. Energy deposition is low near the poles. That's why they are cold.
      - olefoo 17y ago
        Yes, and surface albedo is only one of many factors affecting the global heat budget. Dr. Schneider's site is a reasonably good point to start understanding the complexities of climate change. http://stephenschneider.stanford.edu/index.html http://stephenschneider.stanford.edu/index.html
- yummyfajitas 17y ago
  Putting plants on the roof, fertilizing them, watering them and protecting them during the winter is cheaper than painting once every few years? (This of course assumes your roof is flat and strong enough for greenery.)
mildweed 17y ago
Sounds a lot like duct tape to stave off chemical attacks. If dramatic change is the agenda, go after cars more aggressively.
steveplace 17y ago
Or we could stop using black shingles on houses.
- davidw 17y ago
  I vote for nice red tiles: http://www.flickr.com/photos/82092893@N00/314179676 http://www.flickr.com/photos/82092893@N00/314179676
- ars 17y ago
  Keep in mind that the black singles help in the winter. In hot climates I've seen white rocks on the roof (with tar or a rubber sheet underneath).
  - steveplace 17y ago
    Well i've never lived north of the mason dixon, so I didn't consider that end. What is this "winter" you speak of?
wmblaettler 17y ago
I've thought about this a while back when a co-worker and I were discussing the aesthetics of light colored shingles. Dark ones look better was his opinion, and probably in the opinion of many others. If one were to develop a process by which titanium-dioxide (or whatever, white) paint could be applied to the "top" face of the shingles on a sloped roof (asphalt shingles are covered with small 3-dimensional granules), while leaving the lower faces dark, you would have the best of both worlds: Reflectivity from the summer sun which is high in sky and also heat capture from a sun in the winter when it is low in the sky, plus the aesthetic of a darker roof when viewed from ground level. Just another half-baked idea of mine...

11 points by daviday 17y ago

This simple solution was suggested long ago. It'll help keep the building cooler and the roof will last longer. I'm so bored with these dead simple suggestions and no action.

mahmud 17y ago
They also suggested American school kids hide under their desks in case of a nuclear attack by the USSR! Some "solutions" are more of a psychological crutch, or placebo, than anything.
- steveplace 17y ago
  How is this solution a psychological crutch? If there is evidence that painting roofs white will help cool off cities and reduce your a/c usage by 15%, why not do it? The analogy you provided is not applicable.
  - ars 17y ago
    "If there is evidence that painting roofs white will help cool off cities and reduce your a/c usage by 15%, why not do it?" Is there actually evidence for this? In the real world, not just some calculations? Various people have pointed out flaws such as: it won't stay white. In the winter it makes things worse, and depending on where you live the net is no good. One reason not to do it is that it costs more than it saves. And in the places where it's really bad, like Tuscon, they put white rocks on the roof, so I bet that anyplace where it's worth it - it's already being done!
    - steveplace 17y ago
      Well there's a nice video out there from our most favorite cuddly energy analyst Amory Lovins; he's talking about parking lots but the same premise holds (I think): http://fora.tv/2009/05/01/Amory_B_Lovins_Big_Savings_Through_Integrative_Design#Amory_Lovins_on_Integrative_Energy_Solutions http://fora.tv/2009/05/01/Amory_B_Lovins_Big_Savings_Through... The entire video is fascinating if you've got 2c of coffee in you.

8plot 17y ago

Someone correct me if I'm wrong, but isn't there more energy used to heat buildings than cool them? Of course it depends on many factors, including location; so a blanket statement of "white roofs everywhere" seems wrong.

ars 17y ago
It strongly depends on where you live. But very little of the heat from the roof gets in the building in the winter. Mainly because it's insulated. But also because hot air rises, so little of it travels down to the building space. But A/C is with vents, AKA air currents, so may be more effective at capturing heat from ceilings. But all that ignores the fact that white paint does not survive. In Tuscon the roofs would have white rocks on the roof. I strongly doubt you could make a white roof paint that would survive for more than a few years. How about shiny aluminium roofs? As a side note, I always wondered why metal roofs are not more popular. Aluminium would last pretty much forever, and it doesn't have to be one piece - you can make it into shingles for easy installation.
- jnorthrop 17y ago
  "As a side note, I always wondered why metal roofs are not more popular. Aluminium would last pretty much forever, and it doesn't have to be one piece - you can make it into shingles for easy installation." When I re-shingled my roof a couple of years back I looked into metal roofing. The cost was almost double asphalt roofing shingles. Although a metal roof would last longer (25 years vs. 50 years), but if you wanted durability and cost wasn't an object slate roofs are expected to last 75 years or more (at least here in Maine). Of course a white roof here is useless -- I don't even own air conditioners.
- dan_the_welder 17y ago
  As far as shiny aluminum goes, it's my experience that it does not remain shiny for long. A coating that kept it shiny would increase cost as well as the process of making it mirror finished in the first place. Once the coating failed there would be no practical way to re-polish and recoat to anywhere near factory quality and there goes your efficiency. In Florida a dull aluminum surface will be much hotter than a white painted one. Metal roofs are not as popular as they should be because the capitol cost is more and they are often considered low class. These days there are several fancy metal roofing systems that are more popular than 5 V crimp and the classic corrugated. I personally like the classic standing seam style which I saw a lot of in Maine and New Hampshire and are installed by skilled craftspeople. Asphalt shingles are made from the cheap and plentiful byproducts of the oil refining process and crushed rock. They are made from dirt and installed by low skilled labor.

TriinT 17y ago

How much energy would be spent on the production of white paint? How much energy would be saved by painting the roofs white? Unless a detailed quantitative analysis is provided, this is pretty much nonsensical...

ars 17y ago
The article suggests up to 15%. Assume 10%, and a $1000 yearly A/C bill, that's a savings of $100 a year. Energy spent is pretty much exactly equal to the price of the paint. So how much does paint cost? How much to install, and how long does it last? All theoretical questions, since I don't think paint that can survive on a roof exists. I'm going to make some wild guesses: You need 10 gallons of paint at a cost of $40 per gallon. And it takes about 1 day to install, at a cost of 8 hour*40 $/hour. So total it would be about $720 to install. And I bet it would last 3 to 5 years. Lets be generous and say 5. So it costs $144 per year, but saves you $100. Not a good plan. It uses more energy than it saves. Of course my numbers are totally guesses. Especially the cost for paint that does not exist.
- TriinT 17y ago
  I like your back-of-the-envelope calculations... The problem with such seemingly unorthodox proposals is that they can be either brilliant or totally retarded. The devil is in the details. Unfortunately, neither the media nor the masses care a fig about details...
- yardie 17y ago
  They have paints that are good for 5-10 years. They are white and you'll find them on the bottom of your local swimming pool. It's exposed to the sun everyday with the weight of hundreds of gallons of water on top of it. The paint does exist, but depending on your location you might not be able to find it. I'm sure you can get it if your along the south coast. And it doesn't necessarily have to be paint. Tiles are also useful and they are good for 20 years or more. Almost all new houses I've seen built in Florida for the last 15 years have been using white tiles for the roof.
  - 17y ago

delano 17y ago

I'm not an expert on the matter, but my understanding is that rooftop greenery is a cheaper and more effective way to reduce cooling in the summer and heating in the winter.

Gupie 17y ago
Perhaps however white roofs or roads etc would increase the amount of heat reflected back into space, as per the shrinking ice caps.
- olefoo 17y ago
  Even if we made every roof and every road a pure titanium white, it wouldn't make up for more than a fraction of the albedo change caused by the shrinking of the ice caps. In the US roads cover less than 3% of the surface and all artificial structures together cover less than 10% of the surface.
  - yummyfajitas 17y ago
    The relevant quantity is not albedo x area. The relevant quantity is energy reflected = albedo x area x energy deposition. Energy deposition is low near the poles. That's why they are cold.
    - olefoo 17y ago
      Yes, and surface albedo is only one of many factors affecting the global heat budget. Dr. Schneider's site is a reasonably good point to start understanding the complexities of climate change. http://stephenschneider.stanford.edu/index.html http://stephenschneider.stanford.edu/index.html
yummyfajitas 17y ago
Putting plants on the roof, fertilizing them, watering them and protecting them during the winter is cheaper than painting once every few years? (This of course assumes your roof is flat and strong enough for greenery.)

mildweed 17y ago

Sounds a lot like duct tape to stave off chemical attacks. If dramatic change is the agenda, go after cars more aggressively.

steveplace 17y ago

Or we could stop using black shingles on houses.

davidw 17y ago
I vote for nice red tiles: http://www.flickr.com/photos/82092893@N00/314179676 http://www.flickr.com/photos/82092893@N00/314179676
ars 17y ago
Keep in mind that the black singles help in the winter. In hot climates I've seen white rocks on the roof (with tar or a rubber sheet underneath).
- steveplace 17y ago
  Well i've never lived north of the mason dixon, so I didn't consider that end. What is this "winter" you speak of?

wmblaettler 17y ago

I've thought about this a while back when a co-worker and I were discussing the aesthetics of light colored shingles. Dark ones look better was his opinion, and probably in the opinion of many others. If one were to develop a process by which titanium-dioxide (or whatever, white) paint could be applied to the "top" face of the shingles on a sloped roof (asphalt shingles are covered with small 3-dimensional granules), while leaving the lower faces dark, you would have the best of both worlds: Reflectivity from the summer sun which is high in sky and also heat capture from a sun in the winter when it is low in the sky, plus the aesthetic of a darker roof when viewed from ground level. Just another half-baked idea of mine...