Black asphalt roof shingles absorb over 90% of the radiant heat that strikes them, making them easily over 170 degrees on a hot summer day. A radiant barrier continues to be an excellent solution to block that heat before it enters your living space, but many DIY homeowners and even some professional installers question whether the radiant barrier reflecting the heat back up can actually make the roof shingle much hotter.
Radiant barrier applied either under the roof rafters or under the roof sheathing is probably the most common application of a radiant barrier, but many homeowners shy away from it because they don’t fully understand what radiant barrier is or how it works. There is a misconception that if the heat is coming in through the roof shingles and strikes a radiant barrier only to reflect back out of the roof shingles, then it will be twice as hot. But, that is just not the nature or heat transfer.
Unlike insulation like fiberglass or foam, neither radiant barriers nor the roofing materials hold radiant heat. The radiant barrier reflects 95% of the radiant heat back to the roofing materials, which then emits over 90% of the heat out the roof almost instantly. Florida Solar Energy Center conducted a study on radiant barrier and shingle temperatures and found that the roof increased in temperature by only about 5 degrees at the hottest point of the day, when the heat was entering and exiting the roof simultaneously. This is not significant enough to cause any damage to shingles.
Roofs with radiant barrier have the potential to lower the temp at night because the radiant barrier prevented the heat loss that would typically occur from the traditional mass insulation on the attic floor rising to heat the roof. This means radiant barrier can increase the life of the roof shingles. Traditional mass insulation is often to blame for your air conditioning kicking on in the middle of the night, because once the fiberglass, cellulose or foam has absorbed heat, it continues to emit the heat in all directions, including up to your roof.
By blocking the mass insulation from absorbing heat and emitting it back to the roof, a radiant barrier can decrease the roof temperature at night by over 5 degrees.
Other follow-up research has been conducted on this subject and has reached the same conclusions. In fact, the Reflective Insulation Manufacturers Association recently published a technical paper on the effects of radiant barrier on shingles. As part of RIMA’s research on roof temperatures, they surveyed roofing manufacturers like CertainTeed, IKO Industries, Vande Hey Raleigh, US Intec, Crane Plastics, Louisiana Pacific, and Atlas International. They also worked with independent energy specialists, the Florida Solar Energy Center, and the California Energy Commission.
In short, radiant barrier should not void any shingle manufacturer’s warranty and will not damage roof shingles or any other roofing material. Although, other factors like ventilation and water vapor transmission should be considered, and your roofing materials manufacturer should be contacted if you have any questions regarding your warranty.
A radiant barrier continues to be one of the most cost-efficient solutions for your home because it works with the construction materials you already have, continues to save energy month-after-month, and can be installed for a very low cost.