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Dennis Davidson Posted: Feb 16, 2010 01:34 PM	White Roofs - How much is it helping to save energy? I'm just sitting here looking out my office window watching the snow falling and something occurred to me. If the foam and roof coating industry has less than 10% of the market and only about 75% of all coatings are white, it stands to reason that less than 7.5% of the roofs on all buildings have a white reflective coating. Well...right now nearly 100% of all roofs throughout the Northern half of the country are covered with "white" reflective snow! I understand about the heat island effect and solar reflection but energy usage in this part of the country on avg. is about twice as high in the Winter than in the Summer. Now I'm all for installing white coatings just about anywhere. It's the prettiest thing to look at when your done with a project and the customer loves it too. But after a few years it gets dirty and begins to break down and get chalky. So you go from a 80-90% reflective coating to a dirty, chalky 70-80% reflective surface. So I was just thinking, now if you've lost 10-20% of the 80-90% reflectivity on less than 7.5% of all roofs for more or less 50% of the year when using only about 33% of the yearly energy consumption, how much is it really helping?
Roger Morrison Posted: Feb 20, 2010 07:28 AM	Interesting analysis... White coatings have been a mainstay of SPF systems primarily because white coatings age better than darker coatings, especially acrylics. Now, you see white roofs a being advocated everywhere. However, as far as energy conservation goes, it doesn't make much sense in heating climates and the more insulation you have, the less effective is a reflective coating. Reflective coatings really are beneficial in hot climates on roofs with little or no insulation. As for heat island effect, look at cities where this is a problem. Then in downtown areas, compare the relative areas of roofs vs walls, pavement, etc. Somehow, I really don't think that reflective roofs are going to save the world.
Dennis Davidson Posted: Feb 20, 2010 09:25 AM	I agree with the benefits of a reflective coating in warm climates. I just think it interesting how everyone adopts and excepts the same general ideas for every climate. Because it saves energy in hot sunny climates it must do the same in cold climates too? Reflective roof coating is just the latest greatest "catch phrase" and politicians, government officials and suppliers are all jumping on the band wagon because it sells. I'm still promoting "white reflective" because it's a good sales tool and it makes for a good looking job when finished. But personally, my oldest untouched roof out there has gray coating on it. It's 20 years old this year and has never been re-coated (btw it's flat w/1:12 pitch). It's dirty and has a few bird pecks but it's still protecting the foam underneath and that's what really counts. That's where your real energy savings is. I want to clarify here that we're talking about coatings over foam. Coatings applied directly to a non-foam surface is another story. Primarily because a reflective coating will add longevity when applied to a dark roof surface.
Posted: Feb 20, 2010 10:09 PM	White is pretty till the next day, as for the rest, I will leave it up to you guys to discuss!
Tim Wojnarski Posted: Feb 22, 2010 08:32 AM	Interesting thread, and I must say, I have to agree with everything thus far. One other item to consider is thermal shock. Here's an example. Say you have a nice, humid 90 degree sunny day. "Black roof" surface temperatures can easily exceed 120 degrees. Now you get a thunderstorm pass through and all of a sudden, that surface temp plummets to 75 or 80. That temperature change over a very short time is going to cause said "black roof" to move. In a foam and coating scenario, it isn't a big deal because there are no seams, laps, etc. to deal with. But, from a manufacturers perspective, why take the chance? Go with white and it won't convert that sunshine to heat to begin with. True, it won't help in the cold climates, but it can't hurt.
Dennis Davidson Posted: Feb 22, 2010 10:36 AM	I suppose I could argue with my self on this point. No, white reflective coatings won't help much to save energy on foam roofs (in the North). Yes it does help on non-foam roofs. But, as Timw pointed out, Thermal Shock is a very important aspect for a roof's longivity and the proper white roof coating is, in general, the best answer.
Dan Beecher Posted: Feb 22, 2010 10:12 PM	I prefer the light gray in our Northern climate. White turns to gray in a matter of days with dirt in our area. Can get 15 to 20 years out of light gray silicone no problem. After a couple years the white is going to be in the same reflectivity percentage as the light gray and the gray will look a lot better from the road.

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Dennis Davidson

Posted: Feb 16, 2010 01:34 PM

White Roofs - How much is it helping to save energy?

I'm just sitting here looking out my office window watching the snow falling and something occurred to me. If the foam and roof coating industry has less than 10% of the market and only about 75% of all coatings are white, it stands to reason that less than 7.5% of the roofs on all buildings have a white reflective coating. Well...right now nearly 100% of all roofs throughout the Northern half of the country are covered with "white" reflective snow!
I understand about the heat island effect and solar reflection but energy usage in this part of the country on avg. is about twice as high in the Winter than in the Summer.
Now I'm all for installing white coatings just about anywhere. It's the prettiest thing to look at when your done with a project and the customer loves it too. But after a few years it gets dirty and begins to break down and get chalky. So you go from a 80-90% reflective coating to a dirty, chalky 70-80% reflective surface.
So I was just thinking, now if you've lost 10-20% of the 80-90% reflectivity on less than 7.5% of all roofs for more or less 50% of the year when using only about 33% of the yearly energy consumption, how much is it really helping?

Roger Morrison

Posted: Feb 20, 2010 07:28 AM

Interesting analysis...
White coatings have been a mainstay of SPF systems primarily because white coatings age better than darker coatings, especially acrylics. Now, you see white roofs a being advocated everywhere. However, as far as energy conservation goes, it doesn't make much sense in heating climates and the more insulation you have, the less effective is a reflective coating. Reflective coatings really are beneficial in hot climates on roofs with little or no insulation.
As for heat island effect, look at cities where this is a problem. Then in downtown areas, compare the relative areas of roofs vs walls, pavement, etc. Somehow, I really don't think that reflective roofs are going to save the world.

Dennis Davidson

Posted: Feb 20, 2010 09:25 AM

I agree with the benefits of a reflective coating in warm climates. I just think it interesting how everyone adopts and excepts the same general ideas for every climate. Because it saves energy in hot sunny climates it must do the same in cold climates too? Reflective roof coating is just the latest greatest "catch phrase" and politicians, government officials and suppliers are all jumping on the band wagon because it sells. I'm still promoting "white reflective" because it's a good sales tool and it makes for a good looking job when finished. But personally, my oldest untouched roof out there has gray coating on it. It's 20 years old this year and has never been re-coated (btw it's flat w/1:12 pitch). It's dirty and has a few bird pecks but it's still protecting the foam underneath and that's what really counts. That's where your real energy savings is.
I want to clarify here that we're talking about coatings over foam. Coatings applied directly to a non-foam surface is another story. Primarily because a reflective coating will add longevity when applied to a dark roof surface.

Posted: Feb 20, 2010 10:09 PM

White is pretty till the next day, as for the rest, I will leave it up to you guys to discuss!

Tim Wojnarski

Posted: Feb 22, 2010 08:32 AM

Interesting thread, and I must say, I have to agree with everything thus far. One other item to consider is thermal shock. Here's an example. Say you have a nice, humid 90 degree sunny day. "Black roof" surface temperatures can easily exceed 120 degrees. Now you get a thunderstorm pass through and all of a sudden, that surface temp plummets to 75 or 80. That temperature change over a very short time is going to cause said "black roof" to move. In a foam and coating scenario, it isn't a big deal because there are no seams, laps, etc. to deal with. But, from a manufacturers perspective, why take the chance? Go with white and it won't convert that sunshine to heat to begin with. True, it won't help in the cold climates, but it can't hurt.

Dennis Davidson

Posted: Feb 22, 2010 10:36 AM

I suppose I could argue with my self on this point. No, white reflective coatings won't help much to save energy on foam roofs (in the North). Yes it does help on non-foam roofs.
But, as Timw pointed out, Thermal Shock is a very important aspect for a roof's longivity and the proper white roof coating is, in general, the best answer.

Dan Beecher

Posted: Feb 22, 2010 10:12 PM

I prefer the light gray in our Northern climate. White turns to gray in a matter of days with dirt in our area. Can get 15 to 20 years out of light gray silicone no problem. After a couple years the white is going to be in the same reflectivity percentage as the light gray and the gray will look a lot better from the road.

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