A cooler roof: radiant shingles and radiant barriers

I put a new roof on my house last year and installed radiant barrier under the shingles. I can feel the difference in my upstairs rooms. Check out the article below from Chris Curles and Associates of InfraRED Home Inspections of Atlanta.

There are several ways to keep your cool when electrical bills make you a little hot under the collar during warm weather months.   A cool roof lowers electrical bills and keeps a home more comfortable by reducing the amount of heat that is transferred inside. Cool roofs are designed to maintain a lower roof temperature while the sun is shining.

There are a number of ways a cool roof can be created, including the installation of radiant barriers within the attic as well as radiant shingles on top of the roof.

Radiant heat travels in a line and heats anything solid within its path. When the sun heats a roof, it is the sun’s radiant energy that makes the roof hot. A large portion of this heat is conducted through roofing materials to the attic side of the roof. The hot roof material further radiates the heat energy onto the cooler attic surfaces, including the air ducts and the attic floor. This heat will continue to be conducted down through a home’s walls and ceilings into the rooms below.

Radiant barriers in an attic.

Radiant barriers in an attic.

A radiant barrier in the attic can reduce the amount of heat that is transferred from the underside of the roof to the other surfaces in the attic. Such a barrier is effective because of its ability to reflect back the radiant heat rather than allow its further transmission to areas below. Most barriers available today have a reflectiveness of 95 to 97 percent.

Radiant barriers are more effective in hot climates than in cool climates, especially when cooling air ducts located in the attic. Some studies show that radiant barriers can lower cooling costs between 5% – 10% when used in a warm, sunny climate. The reduced heat gain may even allow for a smaller air conditioning system.

And the greater the temperature difference between the sides of the radiant barrier material, the greater the benefits of a radiant barrier can offer. In cool climates, it’s usually more cost effective to install more insulation than a radiant barrier.

Some of the most popular names in radiant barriers/solar foil include Attic Foil, eShield, Prodex, Green Energy Barrier, SolarGuard and Reflectix.

Landmark Solaris™, a new solar reflective roofing shingle.

Landmark Solaris™, a new solar reflective roofing shingle.

Reflective roof shingles can also greatly reduce the warming effects of the sun by reflecting heat upwards. Although white materials tend to be good solar reflectors, colored roofing materials can also be made to reflect more sunlight.

More than half of the sunlight reaching the earth is invisible to the human eye, and even though it is visually undetectable, this invisible sunlight still beats down on and heats our roofs. A colored surface that reflects much of the invisible sunlight is called a cool-dark color, or cool color. A cool-dark color reflects more sunlight than a similar-looking conventional dark color, but less than a light-colored surface. For example, a conventional dark colored surface might reflect 20% of incoming sunlight, a cool-dark colored surface, 40%; and a light-colored surface, 80%.

Currently, Landmark Solaris, Owens Corning, GAF, and 3M, among others all manufacture reflective roofing shingles in cool, dark colors. Both radiant barrier material and some reflective roofing shingles qualify for an energy tax credit of up to $500 under the Tax Relief, Unemployment Insurance Reauthorization and Job Creation Act of 2010. 

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  1. #1 by Foam Roofing on October 6, 2011 - 6:16 am

    i really appreciate your blog… this is of great information…

  2. #3 by Jonathan on February 2, 2012 - 7:40 pm

    This is very well done. People often doen’t understand the purpose of radiant shingles and the barrier placed in their homes.

  3. #4 by Grass roof installation on March 27, 2012 - 4:34 am

    I found this information extremely helpful, Thanks for sharing.

  4. #5 by Commercial roof replacement on May 15, 2012 - 10:20 am

    This will definitely help someone reduce their electricity, through the use of reflective cool roofs and radiant barriers. These are the best type of energy efficient roof solutions to go with, especially here in Georgia.

  5. #6 by Terry on September 24, 2013 - 10:38 am

    Thank you for the info on heat radiant barriers. Living in Michigan, is there a trade of point between reflecting heat in the summer, and gathering heat for the cold winter months. Does a reflective shingle, such as brown or grey work for both?
    Secondly, in the picture the reflective barrier is installed below the roof joists, with the reflective heat, does this not promote dry rot in the wood?
    Has there been any studies or reports on the above? I am looking to replace a roof soon, and would like to do it economical… and look towards saving energy in winter and summer if possible.

    • #7 by thunsicker on September 24, 2013 - 2:47 pm

      Hi Terry, Thank you for your questions. I am not a roofer, but a real estate agent here in Georgia. I do imagine that different climates would have an impact on what is best for your situation. I live in a Cape cod where the upstairs bedrooms are built into the roof line. In the summers you use to feel the heat coming thru the ceiling and with the radiant barrier under the new shingles its a world of difference. Heat down here in summer is tougher to manage than cold, so that’s never been a concern about keeping heat it for me. I believe that its a better insulating quality in general so it will help retain the heat in the house in the winter, but yes it does prevent it from heating it up like it was before. My radiant barrier was laid just under the shingles, not under the roof joists. I have heard of people adding to the attic, but I don’t have one, so this was the next best thing. My roofer did warn me that it may increase the deterioration of the shingles but I put down a 40 year shingle and if its life is cut down that’s OK with me as the heat barrier was more important than longevity of the shingle. There are trade-offs with alot of things. I have these discussions with my clients quite often when it comes to hot water tanks versus tankless hot water heaters, wood windows versus clad windows etc. I’m afraid if I were building a house now it would be too costly for me to live in!

      With regards to your question of brown or grey reflective shingles I don’t know if there is a difference, this was an insulation under the shingles. I have learned that a metal roof does have a tax rebate because of its energy efficiency, maybe you are thinking about that? Depending on the style of your roof you may want to look into that. Its definitely not economical, but it is permanent and does provide the great insulating qualities, plus you get a rebate!

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