Roof Color

[Perchoutofwater]

Most commercial roofs (flat roofs) in the South are already white or a very, very, light grayish-blue that looks white from a distance. There is no doubt that they help save energy in warmer climates where the AC is run more than the heat. I haven't seen a flat roof in any color other than white in the last 150 projects we've done. I will say that insulation has a lot more to do with it than the color of the roof, but the color does make a difference, if you don't believe me, just go work up on an dark roof for a day or so. I would think in the North you would want a dark colored roof, but again it is more about the insulation than the roof color.

 

One question I have on this is while the lighter color roofs will save energy in the South, what happens to the light/heat waves that are reflected back into the sky? If it is a cloudy day won't that just exasperate the greenhouse effect?

 

Someone mentioned Landmark Solaris shingles form Certain Teed Roofing. I wouldn't use them, they are a waste of money if your intention is to save money. I'm always looking to save money on things like this. I recently got my house re-roofed. I looked into these and got as far as the warranty. They only carry a 10 Year warranty, and cost three times as much as a lifetime shingle. The place a product like this would be most helpful would be in the South, but the South has too many hail storms that could damage them. I wouldn't put any shingle on a house in a southern state that didn't carry at least a 30 year warranty, and for the cost difference I'd go with a good life time shingle like GAF/ELK Timberline® Prestique®.

[Azazello1313]

One question I have on this is while the lighter color roofs will save energy in the South, what happens to the light/heat waves that are reflected back into the sky? If it is a cloudy day won't that just exasperate the greenhouse effect?

 

well I'm thinking the white clouds already reflect most of that light back out to space.

[Perchoutofwater]

well I'm thinking the white clouds already reflect most of that light back out to space.

 

Yes, but if we have all these white roofs, does it not just reflect the light back up into the clouds which would then reflect it back down to the earth again? Seems to me that while a black roof may increase the temperature right at the roof some, that the white roof reflecting it up the clouds and the clouds reflecting it back again would do more to increase the overall temperature of the atmosphere. Not my field, and it may be twisted logic, but it makes sense to me.

[Azazello1313]

Yes, but if we have all these white roofs, does it not just reflect the light back up into the clouds which would then reflect it back down to the earth again? Seems to me that while a black roof may increase the temperature right at the roof some, that the white roof reflecting it up the clouds and the clouds reflecting it back again would do more to increase the overall temperature of the atmosphere. Not my field, and it may be twisted logic, but it makes sense to me.

 

well, figure 2/3 of the light (just a wild ass guess, the exact amount isn't that important) bounces off the tops of the white clouds and never makes the surface. of the remaining third, if it hits something reflective when it gets to the surface, it still has a chance of escaping the atmosphere with a lot of its energy. the greenhouse effect only comes into play once the light is absorbed by something and its energy is converted to heat. basically, anything white/reflective keeps the light (and therefore the energy) bouncing around, and as long as its bouncing around it has a good shot at escaping the atmosphere. something reflective is always going to send more energy away than something that absorbs light, regardless of the weather.

[The Holy Roller]

I've wondered this question before (especially since I've put three roofs on houses in the past year). I thought how clever it would be to have a roof that could change color according to the amount of sunlight hitting it. Dark for cold days and light for those warmer days. Someone is going to get rich on this. As far as the greenhouse effect I'm sure we could get together and get a grant from OB to study this.

[detlef]

Since this has become the defacto topic on roof colors now that the other has been shut down, I wanted to address the issue of not capturing heat in the winter that was brought up. In essence, it's not as big a deal for most areas.

 

Certainly if you live in a place that is rarely warmer than comfortable and often colder than colder than comfortable, it wouldn't make sense. However if you live in, say a place like NC where it's hot as balls a few months a year, very cold for about the same amount of time and mild the rest, it costs a lot more to cool our place than it does to warm it. And this is despite the fact that it never gets as much hotter than the comfort zone than it gets below. After all, the hottest it ever gets is 100 degrees or so, which is 30 degrees hotter than "normal" and nearly unbearable. In comparison, 30 degrees below that (40 degrees) is just simply cold, but nothing putting on a decent coat on can't fix. It has to get another 10-20 degree colder than that before it's perceived to be as bad as a 95-100 degree day.

 

So, despite the fact that we spend as many months of cold as we do of hot and, when it's cold, it gets far colder than "normal" than it ever gets hot. It costs us more to cool than heat.

 

This, of course, is outside temps but does illustrate how much more we're bothered by each degree over normal than under.

 

Then there's the simple fact that heating things is far more natural than cooling them. It's pretty damned easy to heat things, hell, it's an intrinsic part of the laws of thermodynamics. Every time we do pretty much anything, we're creating heat. Even when we cool. Then there's the litany of options one has to heat compared to the options of how to cool.

 

So, it would seem to me that, for anyone who has to heat is house no more often than he has to cool it would realize a net savings by reducing the amount he has to cool it even it makes it harder to heat.

Edited May 28, 2009 by detlef

[Azazello1313]

also, to further detlef's point, you have far fewer hours of sunlight in the winter and at a more oblique angle, so the effect of reflecting energy that might otherwise heat your home in the winter is going to be much smaller than the effect of reflecting away energy that would overheat your home in the summer.

[dmarc117]

how come survival blankets are reflective?

 

 

Reflective surface keeps heat in and cold out. Intended for use as part of an emergency pack.

Edited May 28, 2009 by dmarc117

[Azazello1313]

how come survival blankets are reflective?

 

to reflect back heat your body gives off.

[dmarc117]

to reflect back heat your body gives off.

 

 

A compact, lightweight survival blanket.

 

# Aluminized, non stretch polyester.

# Steys flexible in freezing temperatures.

# Reflects body heat back to body.

# Wind and waterproof.

# Weighs only 1.5 oz. (42.5g).

# Size 53"x82.5" (135x210cm).

# Fits in your pocket.

# This survival blanket weighs 0.13 pounds

[Azazello1313]

exactly. pray tell, what is your point?

[detlef]

exactly. pray tell, what is your point?

I think you're pwned or something but I'm still not sure why. If I figure it out, I'll let you know.

[Cameltosis]

exactly. pray tell, what is your point?

 

If you're in a house with a white roof and you are freezing you will need a reflective blanket! duh

[wirehairman]

Someone mentioned Landmark Solaris shingles form Certain Teed Roofing. I wouldn't use them, they are a waste of money if your intention is to save money. I'm always looking to save money on things like this. I recently got my house re-roofed. I looked into these and got as far as the warranty. They only carry a 10 Year warranty, and cost three times as much as a lifetime shingle. The place a product like this would be most helpful would be in the South, but the South has too many hail storms that could damage them. I wouldn't put any shingle on a house in a southern state that didn't carry at least a 30 year warranty, and for the cost difference I'd go with a good life time shingle like GAF/ELK Timberline® Prestique®.

 

Didn't get past the price, but this additional information makes me fell better about the decision.

[whoopazz]

Green roofs are the rage now for office buildings. Obviously, you would need to engineer the weight restrictions, but you will essentially have a garden on the roof...what better place? Lots of sun and moisture, CO2 capture, reduced urban runoff, and an untapped source of veges in the cities.

 

As far as the white roofs, most of that heat probably reflects back in to the local atmosphere, but at least owners are saving cash short term on cooling costs.

[Perchoutofwater]

Green roofs are the rage now for office buildings. Obviously, you would need to engineer the weight restrictions, but you will essentially have a garden on the roof...what better place? Lots of sun and moisture, CO2 capture, reduced urban runoff, and an untapped source of veges in the cities.

 

As far as the white roofs, most of that heat probably reflects back in to the local atmosphere, but at least owners are saving cash short term on cooling costs.

 

I've built a couple of buildings with these, and they are pretty neat. They are also very, very expensive. It would be almost impossible to do this to an existing building, unless you just didn't care how much money you spent.