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Question DetailsAsked on 4/19/2012

Will light-colored roofing keep my house cooler?

I have read that roofing material that reflects light will make it easier to cool a house in the summer. Some people even paint their roof with special white paint to reflect sunlight. My flat roof is covered with a dark membrane that needs to be replaced. The roofer who installed it says the material is reflective, but it looks black to me. The membrane does have some light-colored grit embedded in it, but the overall appearance is dark as night. Is the roofer blowing smoke up my skirts?

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4 Answers

Voted Best Answer
3
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Here is the real deal on light color roofing. There is no dispute that a light surfaces will reflect more light thus absorb less heat. On a hot day a black roof will easily be 20 or more degrees hotter than a white. BUT one must understand attic ventilation as well as insulation.


Most residential shingle roofs are constructed as a "cold deck" design. This means that the insulation is in the ceiling and the deck, or the substrate, of the roof is ventilated and thus should be "cold". For comparison purposes a warm deck design is when the substrate is insulated and there is no ventilation. A residential flat roof can either be a warm deck or a cold deck.


Now that we've got those boring definitions out of the way, what does this mean? Well I beleive it was AirVent, Inc. in conjunction with the University of Illinois did a study back in about 2000 or later 1990's. Their purpose was to determine the answer to this exact question. What they learned is that with a PROPERLY VENTILATED ATTIC space, the heat transfer from that black to the white shingle only equated to a 2 degree difference in the internal conditioned space.



Yes 2 degrees makes a difference. However my recomendation as a roofing contractor who gets asked this very same question half a dozen times a year is this, "You should consider proper ventilation and increased insulation more so than the color of the shingle if you are worried about thermal transfer."



OK, so that's in regards to a shingle roof. But I mentioned that to make a point. The Department of Energy has studies that show what areas should consider white vs dark roofs, but these studies are skewed because they don't take into account insulation. If someone is relying on a black roof to warm their building in the winter, they've got bigger problems.


What I tell my flat roof customers in regards to reflectivity is that, it's code in most areas to be reflective, at least in Chicago it is. I explain that insulation matters more than reflectivity. Reflectivity on the other hand is essential to the longevity of some roofing membranes such as modified bitumen and hot asphalt built up roofs. I definetly think that on a low slope roof reflectivity is the way to go for most situations.



If you truly want to learn about your flat roofing options, follow the link I refrence in sources and look into thermoplastic membranes such as PVC or TPO. If you are truly concerned with reflectivity make sure the product you have installed is an Energy Star Rated roofing product.



For what it is worth if you find out the name of the other roofing product you currently have, you can find out the reflectivity rating of the product by contacting the manufacturer, or looking on their website. This will tell you if it is truly reflective or not.

Source: http://reliableamerican.us/services/l...

Answered 8 years ago by ReliableAmericanRoof

0
Votes

Good answer Reliable.


Lighter color will be cooler but ventilation is not to be overlooked.



Answered 6 years ago by WoWHomeSolutions

0
Votes

I should have added the fact that the house has no attic. There is a layer of insulation between the roof and the living area below, but that's it.

Answered 6 years ago by Rollax

0
Votes

I should have added the fact that the house has no attic. There is a layer of insulation between the roof and the living area below, but that's it.

Answered 6 years ago by Rollax

0
Votes

In that application, definitely go with the lighter color shingle or an Energy Star rated shingle.



Answered 6 years ago by WoWHomeSolutions




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