More low technology solutions to energy problems. Just ask guest blogger Jody, he's always going on about this. Or Isaac Newton. He knew something about light.
Here's an L.A. Times story,"To slow global warming, install white roofs," reporting on it.
But why not title it, "To reduce energy use, install white roofs"?
Why not, "To save a billion dollars, install white roofs"?
Why not, "To practice more ecologically sustainable living, install white roofs"?
Why not, "To stand out from your neighbor, install white roofs"?
Why not, "To instigate a conversation on the proper social etiquette for wearing a white roof after Labor Day, install white roofs"?
The New Republic pitched in on the matter too.
Yet Treehugger noted this a long time ago (and noted it anew with links to the LA Times story too).
And Grist too, from 8 years ago!
If I dug into the databases I could likely find articles about this from a hundred years ago.
Those stories never stuck. Nor were they constructed within the global warming narrative. It isn't that we don't know white roofs will absorb less heat and thus keep houses cooler and thus require less air conditioning. We are aware that white is a lighter color than black. This is not new or startling information. What is the distance, though, between fact and action?
Why not some other title? Because it wouldn't sell.
So, can you wear a white roof after Labor Day? In the South it'd probably be okay, but be careful if you go to the Hamptons for that party next weekend. They'll glower at you.
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Or why not, "To get prosecuted by your local planning office, install white roofs"? Dunno about your way, but where I am light-coloured roofs are explicitly forbidden by planning restrictions. As are many other environmentally-friendly and efficient construction choices.
Here we use black roofs so that a sunny day in the winter will reduce the snow load your roof trusses are holding. It may even reduce your winter heating bills a bit more than it increases your summer cooling bills, but I'm not sure of that since snow is a good insulator, if your roof doesn't collapse, of course.
On old brick buildings that require tar roofs, the trend here has been towards painting them silver. It's not even visible from street level, though it can be rather blinding when riding the El.
After I tear out all my dark colored solar panels which recycling bin do I put them in?
First, a little building construction advice.
You never want a warm roof. Particularly in snow country. The problems is that as you warm the roof the eaves, being thin sections and exposed to the wind, stay cooler as the rest of the roof warms in the sunlight.Which means the snow stays on the eaves even as it melts on the rest of the roof. The result is an ice dam with water from the melting snow backing up behind it. This causes the roof to leak, structure to rot in time and huge chunks of form. It is not unknown for this ice to fall off and hurt people.
A cold roof has its own problems, condensation mostly, but most of these are solved by proper ventilation and a good vapor barrier.
The energy advantages of a white roof have long been understood. All the studied I have seen say white shingles save you money. And savings are even greater if other, more reflective materials, are used. I understand that in the SW commercial buildings use a particular sort of highly reflective 'roof powder' to help reflect the heat from their flat roofs. I'm not sure why this is better than painting the roof deck white or using aluminized paint but apparently it is.
The reason you see so many homes with dark roofs has to do with curb appeal and perception. Generally light color objects tend to look closer, larger and focus attention. Dark colors tend to look smaller, farther away and deflect attention.
Psychological testing involving people shown slides and asked to either estimate the size and/or the worth of a house shows that the body of the house and roof effect perception in a complimentary way.
A house shown with white body is perceived as being larger, more desirable and worth more. But the roof either compliments this perception or counters it. A dark roof looks smaller compared to the house and compliments the lighter color making it look larger. A light roof competes with the house and causes the body of the house, the part you live in, to look smaller.
A light house body and dark roof consistently gets perceived as larger, roomier, friendlier and worth more. All the things a buyer is looking for.
A darker house body with a light roof gets seen as smaller, darker, cramped and less desirable.
Builders are building houses to sell. And part of this is selling a dream.
Huge picture windows that increase cooling cost, represent a huge hole in the insulation system and violation of privacy are part of the dream. So you can always count on there being at least one.
Dark roofs, picture windows, soaring entranceways, short overhangs (long overhangs make the building look squat) are all sops to a buyers perception and memes within the culture. They help sell houses and any builder who would leave them out is putting himself at a huge disadvantage. Most will only do it for a custom built home that is sold before it is built.
Yes we could benefit the environment and save energy costs by having white roofs. But your going to have problems getting people to build them that way because your going to have problems getting people to buy them. Classic chicken and egg.
What is needed is a roof material that is perceived by the human eye as dark but one that reflects back sunlight like a white roof.
Thanks for the info, Art. I already knew about the ice dam issue, but the psychological part is new. Not surprising, now that I think about my own reactions to houses. However, you say:
No such animal. The peak of the solar energy density spectrum is in the middle of the visible (that's why our eyes are sensitive there!), so anything that looks dark will be absorbing sunlight. There might be a clever psychological solution involving a dark border, or stripes, or something, but the main area of the roof will have to look white if it's to reflect solar radiation.
Me, I solved the problem by buying a 1920 Cape Cod with a full-width shed dormer on the South side, so most of the area exposed to direct sunlight is not visible from the street. When I had to replace the roof on the dormer (cause shingles don't work on 1 in 12 slopes, no matter how much the former owner may have wished it so), I put down white EPDM. Now my attic fan, which used to run every day in the summer, runs almost never. Maybe five times this whole summer. And you'd never know it from the street. Hah!
The rest of the roof would be relatively light colored too, except for the mildew...
"No such animal. The peak of the solar energy density spectrum is in the middle of the visible (that's why our eyes are sensitive there!), so anything that looks dark will be absorbing sunlight. There might be a clever psychological solution involving a dark border, or stripes, or something, but the main area of the roof will have to look white if it's to reflect solar radiation."
Perhaps the problem is one of scale. On a chemical, material sciences, scale I had suspected that pretty anything that reflected sunlight wold have to be light in color.
But there are differences in what is exposed to solar radiation and what a person sees when judging the critical 'curb appeal' that sells, or fails to sell, houses. I note that curb appeal is a low angle view. Whereas the solar radiation, particularly in the south, where solar exposure is the greatest, is coming down from on high. There should be some way of taking advantage of this difference to have the roofing material, in effect, two different faces.
Perhaps, concentrating on shingles, each shingle could have an upright at the low side. This would act like a tiny billboard. A billboard that presents a pleasingly dark face to people on the ground. But one that would keep the white nearly horizontal face exposed to the sun concealed.
Alternatively a shingle made of small tubes oriented toward a viewer on the ground. Seeing the tube edge-on the view would see a dark shadow. But sunlight, coming from on high, would be reflected by the light colored and highly reflective side of the many tubes.
Seems to me there is the beginning of a workable solution in there somewhere.
One could certainly build steps into the shingles, so you would see one face while the top was a different color. But then you're stuck with the top surfaces being a low angle, which gets you back into the situation where the water doesn't run off and instead leaks into your house to the point where it inverts the drywall tape in corners, forming big tape-balloons of water. Not that I'm sensitive to roof leaks or anything.
But wait, go back to the chemical or material idea. I think you have something there! You basically make something that reflects differently from different angles. It could be a chemical thing like a color-changing ink, or even something more macroscopic. So long as the ridges you're making are small compared to a typical water droplet (say, a mm or two), it should act like a normal roof as far as drainage goes. So, tiny steps with reflective horizontal tops and dark risers.
Dirt would have a tendency to settle on the flat surfaces, so you'd have to make them large enough that water would wet them and wash off the dirt. Other big issues I see include tailoring the material to the roof slope, and what to make it out of. You wouldn't be able to use asphalt-fiberglass style material; the roughness scale is too big. Something like an EPDM with the right extrusion mold might work. Then you have to color it, with something colorfast against 20 years of UV exposure, and with different colors on the different faces. That could be tricky.
It would certainly look different from standard shingles, as well as costing more, but a little creative marketing could easily turn that into an asset. "Why have that old-fashioned asphalt shingle look when you can save big on your cooling bills with new Ebony&Ivory® roofing!"
Of course even better would be if the organic-dye photon transport materials they're trying to commercialize up in Cambridge (our fair city) MA work out, and you make the roof dark by routing all the photons to the edge of the roof where they turn into electricity. I suspect that's a ways in the future though.
Last summer, my land lady had our roof painted white. Living up on her third floor, it made a huge difference (or so I told myself). Its true that there were some negotiations. The top of the house was done in white because it cant be seen from street level, but she decided (after a lot of consultations with a contractor friend) to paint the lower roof (around the porch) a red, which Id never seen before. The question in all of this was glare. In any case it was pretty great.
The small outfit that did the coating was very excited. The guy who runs it normally works in commercial districts. He wanted to do an extra awesome job on her roof since he took a good look around the neighborhood and saw the potential (a bunch of 1860-1900 homes with big flat roofs). Its ease and cheapness compared to green roofs make it a pretty great option.
But Ben wonders why all of the attention all of a sudden. Its true that the strength of the climate change trope has made these discussions possible. But theres also a technical hitch: nano-processing, which makes the production of TiO2 faster and cheaper with a higher quality end product, has been underway for the past couple of years, which makes the pigment (used in everything from sunscreens to house coatings and now roof coatings) more accessible than before or so Id posit.
Really wonderful post and wonderful comments especially I m inspired by Jody and his neighbour ideas, keep it up with sharing great ideas, :)
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I'm totally agree with every idea that could help survive our planet and even when it will lower global warming or anything by 0,01% I will take it for sure. Maybe we won't suffer from destroying our planet but our grandsons may so think about them now.
It is a nice post and, I do believe that if white roof coating is consist of RV Roof Sealent than it is better. Because EPDM is a guard of roof from weather, water and temperature and enhance life of roof.