It feels good to be ahead of the curve sometimes. About this time last year, I was slaving away painting my roof white – much to the bemusement of my Northern Virginia neighbors and friends. So I couldn’t help feeling just a little smug this morning as I read that US Secretary of Energy Steve Chu is also a great fan of roof-painting to combat global warming…
Perhaps the whitest roof in Northern Virginia
According to The Independent newspaper,
Steven Chu, the US Secretary of Energy and a Nobel prize-winning scientist, said yesterday that making roofs and pavements white or light-coloured would help to reduce global warming by both conserving energy and reflecting sunlight back into space. It would, he said, be the equivalent of taking all the cars in the world off the road for 11 years.
Speaking in London prior to a meeting of some of the world’s best minds on how to combat climate change, Dr Chu said the simple act of painting roofs white could have a dramatic impact on the amount of energy used to keep buildings comfortable, as well as directly offsetting global warming by increasing the reflectivity of the Earth.
A couple of years ago, we moved into a house with no loft space – just a few inches of paltry insulation between the standard-issue dark-shingled roof and our main living area. And in the summer, things got hot. Really hot. The solution seemed obvious – paint the shingles white, to reflect the sunlight and prevent any unnecessary warming.
Now painting your roof is not something that East Coast folks seem to go in for, and it took a year to pluck up the courage and act on my convictions. But come the warm weather last summer I decided that enough was enough. So I purchased vast quantities of Hy-Tec Thermal Solutions Insul Cool-Coat white paint, power-washed the roof (an adventure in itself), and spent three back-breaking days painting the shingles white.
I’d like to report that, in a controlled comparison, the impact of the paint was immediate and stunning. Unfortunately the AC unit packed in half way through the painting exercise so a strict A/B comparison was out of the question – just my luck! Nevertheless, the qualitative and quite unscientific results of the new paint were pretty impressive – the upstairs rooms in the house underwent a figurative transformation from fiery furnace to cool cave! More significantly, the temperature under the painted shingles was some 30 degrees Farenheit lower than that under the unpainted shingles on the garage under the mid-day sun – suggesting that an awful lot of the sun’s heat was no longer infiltrating the house.
The whole point of the exercise was to reflect as much of the sun’s heat as possible, rather than it being absorbed by the previously dark roof and subsequently having to be pumped out (at considerable expense) by the air conditioning. The paint I used also acts as an insulator. It’s crammed full of hollow microspheres that inhibit the flow of heat through it, as well as reflect back the sun’s light. I think it worked – certainly the new AC system seems to be under less strain in the summer, and the house feels significantly more comfortable. But by increasing the roof’s albedo, I was also able to do my (admittedly small) bit to counter global warming by reflecting away more of the sun’s energy.
It’s not an idea that has had much traction around here – yet. I suspect the only way I’ve got away with it is by exuding an aura of eccentricity – at least the neighbors could whisper “well, he’s British you know…” But now that Steve Chu has enlightened the world to the benefits of roof-painting, who knows where we’ll be in 12 month’s time – forget about going green, maybe the “white revolution” will come to McLean Virginia – and I will be able to proudly say I was there first!
Of course, regular roofs are probably trickier to paint than ours, which has a reasonably low pitch. And I suspect not everyone will appreciate the aesthetic of white shingles or (shock horror) white painted slate. But it has to be said, as a cheap and achievable solution to a significant problem, roof-painting has a lot to recommend it – a little bit of personal geoengineering to make the earth a better place!
It just took a savvy Nobel prize-winner to let the cat out of the bag!
Very cool ! (pun intended). And Christmas all year round. Guess you’re looking at what – 3 yearly repaints? The eccentric minority often leads the way – and is usually ‘right’
Three yearly repaints – you’ll be lucky! The durability question did worry me – seems to have weathered 12 months OK, but I’m hoping for another 24 at least before I have to do the roof-walking stuff again.
Have you done an overall comparison of heating and cooling costs though? Surely the dark roofs weren’t just an aesthetic consideration, but were designed to attract heat in the dead of winter? And if you’re spending more to heat your home now that the roof’s white and you’re using fossil fuels to heat it….well, you see where I’m going with that.
I think it looks nice, actually.
Unfortunately, replacing the HVAC and fluctuating fuel costs prevented a before and after heating/cooling cost comparison. It seems reasonably sure that cooling costs are lower that they would otherwise be, but I’m not sure about the heating. Interestingly, I had heard that before widespread air conditioning was available, white roofs were more common as a way of preventing heating in the summer – and the move to darker shingles is on aesthetic grounds (and perhaps cost, although that’s speculation). But I have no proof for this.
The lack of solar heating in the winter is something that concerned me, although I’m not sure how significant solar radiation heating via dark shingles is. However, having a white roof should in principle reduce radiative heat losses from the house.
Clearly though, the perfect solution would be paint that can change color at the flick of a switch – white in summer, black in winter! Now where have I seen something like that… e-ink! E-ink consists of microcapsules of white and black pigment – applying an electrical pulse simply switches which pigment is visible.
So here’s an idea – paint roofs with e-ink, then simply switch from light to dark with the changing seasons. You could even have embedded messages for high days and holidays 🙂
Can you please talk about infrared light? Do you know if it is significant to a project like yours?
The white pigment in paint like the stuff I use is a broad band reflector – reflecting everything from infrared through visible light to UV. Reflecting the infrared reduces heating – the primary aim of the exercise, and what should in principle lead to lower cooling bills. But it is the UV that is reflected that could help combat global warming – assuming enough surfaces were coated.
Ahead of the curve as always Andrew! Of course, not relevant in Scotland as we’re still huddling together to keep warm even in the ..ahem.. height of summer. Love your portayal as a british eccentric. Do you also wear a smoking jacket around the house?
Only when I think I might be seen 🙂
Here is a link to the study report presentation that regenerated interest in this idea. http://bit.ly/Wd15b.
Since I live in the cold (but getting warmer) UK, I was wondering whether there is something that looks black or transparent in the visible, but reflects UV. A quick Google search showed that there were coatings that claim to do this for textiles e.g. coldblack®: Sun Reflector – UV Protector (http://bit.ly/y49B0). However this approach, or the white paint approach, would be a difficult sell where there is no air-con energy costs to recover. Also I can imagine Sunday morning scream-thuds of DIY-ers falling from their pitched roofs!
Thanks for the study link Mike – extremely useful (~10 m square white roof estimated to offset 1 ton CO2 emitted)
There definitely are options for IR-transparent, UV-opaque coatings – using nanoscale TiO2 particles for instance should be able to provide an appropriate transmission window. But you obviously loose out on the thermal conversion that would result in absorbing the UV as well.
And realistically, the difficulties of “retrofitting” white roofs are substantial – love the macabre image of the Sunday morning DIY-ers 🙂
I was thinking along those very lines before I go out of bed this morning. And then to see this article was a wonderful synchronicity.
Go for it 🙂 I’m still amazed at the difference the white roof makes in Summer. There are days (before the high humidity sets in) where I’m enjoying open windows and cool breezes while all around I can hear neighbors’ AC units humming.
So how did you choose the particular product you used? (Hy-Tec Thermal Solutions Insul Cool-Coat white paint)
And did it matter to you that it was not on the DOE Energy Star list (http://www.energystar.gov/index.cfm?c=roof_prods.pr_roof_products)?
thanks herb
I painted my roof white using 5 cans ( 18 L – at US$70 each) of Sherwin Williams self cleaning , water based ECO Metalatex paint. I used WAP pressurized water to clean the roofs (RED CEMENT) first then after it is dry , I painetd.
It took a week to paint 333 sq, but I have thus, offsets 33 tons of Carbon.
My house looks taller and beautiful and the neighbors came to look and are painting theirs too!
Then I convinced the Mayor of the city to paint the roofs of 2 schools and he even committed to 16 more schools.
Then it caught on and we painted hospital’s roof white.
At the International Rolex Sailing Week, we painted the Yacht Club’s roof.
Now the government in Brazil had committed to me to deliver, in the next 3 months 35,000 low income houses – 1/3 roof area will have solar panels for heating water, and 2/3 of the roofs areas are being painted white.
They are also thinking of painting 180,000 homes all white as well!
I cannot paint the world alone. Please help?
If we all get up and help a little we might have the hope to solve Global Warming effects just like we did with Ozone hole; which by 2009 is only slightly below normal .
Please post your pictures on our website and we will send you the logo/certification
One Degree Less – White Roof Campaign (Global Cooling Initiatives).
I , the Polar bears and the children who still sleep in the street in the hurricane affected areas thank you!
Thanks Thassanee.
For those interested, there’s more information on this initiative at http://www.onedegreeless.org
So why don’t we put mirror on top of the roof? If this suggestion is accepted, I’m gonna open a mirror roof company.
I live in Virginia. What you gain in the summer will be lost in the winter.
True, we don’t have the benefit of the sun heating the shingles in the winter. But the rate of radiative heat loss from the roof is lower than if it was darker, and the paint is also an insulator, so things aren’t too bad. And I must admit that the comfort levels achievable in the summer inside the house, now we have the white roof, far outweigh any small disadvantages in the winter!
I have been coating roofs white in Philadelphia for four years now; and have achieved some impressive results in lowering my customer’s air conditioning expenses – savings for some of over $100/month in the heat of the summer, using roof coatings that are guaranteed by the manufacturer for ten years. At the same time, I’ve learned from mistakes. Professional Roof Coatings may last a long time, and some of the better ones get cleaned by the rain naturally, they are not, however meant for shingled roofs. Last summer, I ruined a client’s suburban shingled roof by coating it. The coating trapped moisture under the shingles causing leaks to develop at many of the nail locations. I have information on http://www.bioneighbors.com about my experiences, and am happy to answer questions that my website does not address.
Lets work together to create smart solutions, so our grandchildren can live even better than we did!
One important dynamic about cool roofing that most people miss, is that cool roofs last significantly longer due to less extreme changes in temperature. The worst thing for a roof is for it to heat up over a hundred degrees in the winter sun, and then drop below freezing at night. This expansion and contraction causes the roof to crack and need replaced more often than a cool roof, which maintains a more consistent temperature. Black roofs can heat up over 180 degrees in direct sunlight in the summer. When it comes to losing beneficial heat gain in the winter, the truth is that in most climates North American climates the reduced cooling costs in summer far outweigh the savings in heating costs. This is because the sun is less direct and less intense in the wintertime; also the sun is more likely to be hidden behind clouds. Personally, I have a cool roof to save on roofing expenses and thick attic insulation to save on heating and cooling expenses. Again, reach out to me at http://www.bioneighbors.com, if you want to learn more.
Something that really helps me is my huge tree’s…. keeps my house cool. So lots of trees would probably help the g-warming too…. I just made that discover and should be a nobel prize winner 😛
– Jaime
Omaha HVAC
This is a very useful information for my husband who is going to re-paint our home this weekend as part of his do-it-yourself home improvement project. In doing so, he bought gallons of insulating and heat reflective paints from add4green.com because he is convinced that using such paints to re-paint our home’s roof, interiors and exteriors will help us save energy and reduce our heating and cooling cost. As a housewife who deals with budgeting my husband’s monthly income, I think any kind of saving is worth the trouble.
Ha – let me know how it goes! Having just moved into a new house – without a painted roof – I’m really missing it! The differences in heat coming down through the roof on a hot day were very noticeable.
Giant micro-foil clad reflectors with a ultra-thin backing of synthetic, miles above the earth used as a reflectors, may be earth’s best chance to avoid global warming short term. Start now (it’s hard to work in the heat).
A promising solution for roofers and homeowners who wants a much cooler house. We also hope not to forget the trees that gives shed. Planting more trees is equivalent to white roof. Planting more trees means cooler place in the future.