Radiant barriers are a tremendous value in warmer Southern climates, helping reduce radiant energy from heating the attic that result in lower attic temperatures helps reduce cooling costs. But do all radiant barriers perform the same? Do all perforated radiant barriers dissipate moisture? Why not simply use spray foam? Let's dive into these questions, learn how radiant barriers work, and see which product may perform best in your customers' homes.
Do Radiant Barriers Really Work?
Radiant barriers help reduce summer heat gains in attic spaces. When the summer sun shines on the roof, radiant heat is transferred into the attic space, heating anything solid-including rafters, joists and ducts. This heat is then transferred into the home's ceilings, which forces the air conditioning to work harder to cool the house.
As the U.S. Department of Energy (DOE) explains, a radiant barrier can reduce the amount of heat emitted into the attic, and therefore, into the house. With at least one reflective surface a radiant barrier works by reflecting the energy back, so heat is dissipated into the atmosphere.
The Florida Solar Energy Center (FSEC) at Cape Canaveral found, when used in attics with R-19 insulation, radiant barriers can reduce summer heat gains in the ceiling by 16 to 42 percent.
Aren’t all radiant barrier OSB products the same?
“LP® TechShield® Radiant Barrier is different,” says Jeff Yelle, director of OSB/EWP Technology. “It’s unique as it was the original and offers patented VaporVents™ Technology.” The perforated radiant barrier is specifically made to prevent moisture build-up, drying more quickly during construction.
"When OSB sheathing is installed during construction, delays are typical. This increases likely exposure to rain," says Yelle. "After the roof is installed, any moisture that collected on the surface of the radiant barrier must escape. If it's a sealed radiant barrier, moisture has nowhere to go-it can't dissipate into the atmosphere. This elevates the risk of moisture problems down the road."
Breathability is important in any radiant barrier—and that’s one of the advantages of VaporVents™ technology. LP TechShield Radiant Barrier is made by creating incisions into the aluminum and OSB after the lamination process. Doing this afterward ensures incisions won’t be clogged by adhesive. “The vents are small enough that it doesn’t impact energy to reflect but does allow the product to breathe, allowing any moisture to escape through the attic vents,” explained Yelle.
Does it matter which side is installed down?
To perform properly, radiant barriers must be installed facing an open-air space. Radiant barriers work not by reflecting heat, but from keeping them from emitting heat in the first place. The vapor vents in a radiant barrier should face the roof, as noted in the installation instructions.
Can spray foam be used as a replacement?
As we discussed in an earlier article, using spray foam to replace radiant barriers doesn’t increase energy-efficiency performance. Radiant barriers help keep heat from emitting into the attic space in the first place, cooling attic temperatures by up to 30º F. Spray foam slows conductive heat flow from the attic into the living space and can possibly trap moisture during construction or following a roof leak.
Can insulating spray foam still be used?
"In order for the radiant barrier to work properly, it has to have an air gap. LP recommends a minimum of 3/4-inch air space between the barrier and the foam," said Yelle. Spray foam works well as a complement, rather than a replacement, to radiant barriers.
Why should I install LP® TechShield® Radiant Barrier?
“LP TechShield Radiant Barrier gives you and your customers tremendous peace of mind that moisture build-up won’t be an issue—either following construction or down the road,” says Yelle. “No builder wants to come back because of a moisture problem.”
For more reasons to install LP TechShield Radiant Barrier—including the 20-year warranty and that it can reduce attic’s temperatures by up to 30º F—be sure to read this article.
Interested in purchasing a radiant barrier? Use our product locator tool to find out where to buy LP TechShield Radiant Barrier.
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