Will Installing AtticFoil® Radiant Barrier Foil Cause Damage To My Roof?
Does Radiant Barrier Cause Roofs And Shingles To Overheat?
One common question we get is, “If I install a radiant barrier on my roof, will it overheat the roof and cause damage to my roof and shingles?”
The short answer is NO. Roofs with a Radiant Barrier will see temperatures increase by only a few degrees - usually between 2º - 10º degrees Fahrenheit. This slight increase is considered a nominal increase because typical roofing systems are designed to handle temperatures well above the maximum temperature they actually reach in real-world applications. Most shingle manufacturers warranty their product over a radiant barrier and, in fact, some areas REQUIRE a radiant barrier when doing new construction.
This can be a little tricky to understand since it seems logical that the roof would get hotter if the radiant barrier below it is reflecting 97% of the radiant heat back through the roof assembly.
What Determines Roof Temperature?
There are two main variables that will determine the maximum temperature a roof will reach: color and ventilation. First, the roof color is the biggest factor; dark colored roofs can easily be 20ºF+ hotter than light colored roofs. Second, air temperature and wind movement over and under the roof affect the temperature. The roof absorbs radiant heat from the sun, but air flow (either wind or attic ventilation) has a “cooling effect” on the roof and helps bring down the temperature. The “cooler” a roof, the less radiant heat it emits. (In theory, if your roof never got any hotter than the outside air temperature, then a radiant barrier would not be needed. This is why homes in complete shade don't benefit much from installing a radiant barrier.)
Based on these variables, every roof will reach a point where the maximum temperature stabilizes. This happens when heat being absorbed from the sun and heat being lost due radiation, ventilation and air temperature, all equalize. A typical roof on a hot, sunny day will stabilize between 140º - 180º WITHOUT a radiant barrier installed beneath it.
Where Does The Reflected Heat Go?
Installing a radiant barrier underneath the roof will cause the roof temperature to increase by a few degrees (usually 2-10 degrees). The heat that would normally be absorbed by the insulation is now being bounced back to the roof deck, and causing the roof to emit more heat upward, rather than both upward AND downward. The roof still is gaining and loosing heat. The radiant barrier is basically DIRECTING the heat AWAY from the attic and the attic insulation.
To understand this better, consider a room with one light source (in the form of a light bulb) hanging in the middle. Under normal circumstances, the bulb sends out light (and heat) in all directions, illuminating the room. Now, add a reflector behind the bulb and the light (and most of the heat) is directed downward. The amount of light (and heat) the bulb produces has not changed; what has changed is the direction the light (and heat) is going. This is the same with a radiant barrier. The amount of heat on a roof hasn’t changed (by much), it’s just that now instead of heat radiating in all directions (upward and downward from the roof) it’s mostly being radiated (forced by reflector - radiant barrier) upward and away from the attic.
Your Roof Will NOT BAKE If You Install A Radiant Barrier.
So, adding AtticFoil® Radiant Barrier to your roof redirects the heat being absorbed by your home and therefore keeps your attic, and ultimately your home, more comfortable and energy efficient. The small increase in your overall roof temperature is not enough to have a significant impact your roof, shingles, or any other part of the roofing assembly.
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| Images from video above. This image shows where the AtticFoil® Radiant Barrier Foil is stapled inside the attic on the bottom of the roof rafters. Three rows (12 ft) on the left side with a single piece in the middle going off to the right to help illustrate the effect radiant barrier has on roof temperature. | Inside the attic. Three pieces of AtticFoil® Radiant Barrier Foil Insulation on one side with the one strip extending off to the other side. |
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| Overlay of thermal image over regular image. You can clearly see where the foil is stapled up. There is about two feet at the bottom (below top plate of wall over soffits) with no foil and about 18" from the top due to where the three pieces ended. We also did not put foil over the last rafter bay on the left to show clearly where the foil ends. | This image clearly shows the roof over the radiant barrier is 7ºF hotter (white is hotter) than the area without a radiant barrier (redest areas). Typically, the roof temperture over a radiant barrier will increase less than 10ºF which should not have a significant impact on the performance of a roof. |
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| White asphalt shingle roof. West facing slope late afternoon 97ºF. A white roof is typically 20 degrees coolor than darker color roofs. | Thermal image of white roof = 156ºF. Even though it is "Cooler" than a dark roof; it STILL emits huge amounts of radiant heat because of the thermal mass of the roof. It is still VERY hot. A radiant barrier is the only method to EFFECTIVELY reflect heat being emitted into the attic. |
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| Here is a dark colored roof with a max temperature of 178ºF. The dark roof may be 20 degrees hotter than the white roof, but BOTH roofs are emitting HUGE amounts of radiant heat into the attic to be absorbed by the attic insulation which will eventually transfer heat into the home. | It really does not make a big difference if the roof is light or dark. They BOTH get HOT, HOT, HOT and will pass this energy into the home. All homes: light AND dark roofs NEED a radiant barrier. |