3 Misconceptions About Radiant Barriers for A Cool Roof

Updated: Jul 20, 2018

Radiant barriers can often get a bad rap. So, as a homeowner, you may wonder why so many contractors and experts recommend them. The truth is that, as with so many other aspects of roofing, the technique and expertise of the installer are vital. Here are three misconceptions you may have heard.

1. It's a Great DIY Project

The presence of a radiant barrier under your roof doesn't necessarily guarantee that it's doing anything. Only if it's placed and oriented correctly and with good installation technique will it be able to effectively shield your attic from the intrusion of radiant heat via the roof deck. Many homeowners make it a DIY project and then feel cheated, not realizing they did it wrong.

Since the installation process is fairly quick and easy for someone who knows what they're doing, hiring an expert roofing contractor to do it for you should be relatively affordable.

2. It's the Equivalent of Tinfoil Hats

On the other end of the scale, you may have heard that radiant barriers are basically a scam and won't help at all. Someone who's had a bad experience with their radiant barrier could hold this opinion, but there's probably a very good reason their barrier didn't work. There are several common installation mistakes, such as installing the barrier backward or on the attic floor.

If the radiant barrier is installed by laying it on top of attic floor insulation, it's too far away to reflect heat powerfully through the roof (and at the wrong angle besides). In addition, horizontally installed radiant barriers can become dusty and lose their reflectiveness, and even worse, they can encourage mold in the attic floor insulation by preventing proper air access.

The law of diminishing returns could also apply here; if you have a super-reflective roof already, for example, you're likely to see less improvement after installing a radiant barrier than if your roof is a heat hog. On the other hand, if your environmental efforts have led you to install an eco-friendly reflective roof, maybe even a small improvement is worth the effort.

3. It Damages Roofing Shingles

If your roof is highly heat-absorbent and susceptible to heat damage, you might worry that radiant barrier is making your roof wear out faster. But in most cases, you don't have anything to worry about. 

The fact is, whether or not a radiant barrier is a great choice for your asphalt roof will depend partly on your local climate, partly on how dark the roof's color is, and how well your other roof-cooling measures, such as ventilation, function. You don't need to worry about straight-up heat damage; you'll likely see only a five-degree increase (such as from 170 to 175 degrees).

However, since the radiant barrier can also slightly decrease the temperature of the roof at night, it may be less beneficial for a roof that's currently suffering from thermal shock. Thermal shock occurs when your roof heats up and cools down extremely rapidly each day and night. This can happen if you live in a hot climate on the coast and get cool sea breezes each night.

Most people don't have this problem but check with your roofing contractor if you suspect your roof has a problem with thermal shock. Signs of thermal shock include cupping, buckling, or tearing shingles and increased loss of reflective granules. If your roof has this problem, you may need to improve ventilation and add shade or even a cool roof coating.

These are just three misunderstandings about radiant barriers that are rampant in America today. As you can see, it's often the placement or installation technique that's to blame for a failed radiant barrier. If you'd like more information on the cool roof projects we can help you with, get in touch with Top Dog Roofing today.