The Best Home Radiant Barrier Foils

Radiant Barrier Properties

• Reflectivity, emissivity, and sun angle control radiant barrier efficiency. Reflectivity measures how much heat is "bounced back" from a surface, emissivity expresses how much is re-radiated, and sun angle helps determine the amount of solar radiation reaching each square foot of the roof.

Radiant Foil Chips

• Radiant barrier "chips" combine traditional blown-in insulation and radiant barrier reflective foil. It offers a significant reduction in radiative heat transfer, but this concept is prone to problems. Chief among them gradual build-up of dust on the reflective surface which eventually causes the insulation to actually trap heat. It is generally less effective than an attic-mounted radiant barriers, and present a moisture retention problem as well.

Foil Beats Spray

• "Radiant barrier" paint sprayed on the underside of the roof inside the attic is not really a radiant barrier at all. A radiant barrier must have an air space between the heated surface and the barrier to work right. Reflective paint applied directly to the underside of the roof was tested as 20-70% less effective than a properly installed foil barrier.

SIngle, Double-Sided

• Radiant barrier foil is composed of either an aluminized plastic film or heavy aluminum foil bonded to abase material. These foils may be stiffened with a web pattern between the foil and backing. The backing material is essential because foil alone easily rips. Two-sided foil has a similar efficiency to single-sided foil but it is stronger and more durable. The two foil surfaces are separated by a base material of paper, cardboard or plastic.

Installation Affects Performance

• Proper air flow is crucial for a radiant barrier to work right. The barrier might be applied directly to the underside of roof decking during construction, or draped over the rafters. According to the Reflective Insulation Manufacturers Association International (RIMA). Stapling the foil directly to the underside of the rafters provides best performance. This method allows for the maximum air flow and durability. Using a double-sided foil with a sturdy center support and stapling it under the rafters offers the best radiant barrier installation results and longevity.