A simple savings calculator tool is available here: Oak Ridge National Laboratory's Radiant Barrier Calculator. In climates where summer heat gain from the attic is minimal, the advantages of a radiant barrier diminish. However, if the HVAC duct work is in the attic, a radiant barrier keeps it cooler during the summer, which can be a significant benefit. Attic insulation levels have a large impact on the amount of heat flow that is reduced by 40% in other words, if you have little or no insulation in your attic, a 40% reduction is very significant, but if your attic is insulated to R-30 or better, there is very little heat flow to reduce. This means that the portion of the cooling load represented by the attic is reduced by 40%, which typically equates to 8% to 12% of the annual cooling costs.įurther clouding the savings question is the impact of attic insulation levels and geographic location. This does not mean a radiant barrier will reduce the homes’ energy use by 40%, as many advertisers claim. A radiant barrier system can reduce the heat flow into the house from the attic by approximately 40%. Two things affect the performance of a radiant barrier system: the level of insulation in the attic and the geographic location of the home. Third, its vapor permeability is very low. Second, it emits (gives off) very little heat. First, it reflects thermal (long-wave infrared) radiation very well. Figure 1. There are three potential locations for an attic radiant barrier – adhered to the underside of the roof decking, hanging from the rafters, or on the ceiling insulation (Source: Radiant Barriers: A Question and Answer Primer 2005).Īluminum foil, the operative material in attic radiant barriers, has three physical properties of interest. Other types of radiant barriers such as “chips”, foil faced air bubble-packing, and multi-layer products, are acceptable for location 3 (more below). Only locations 1 and 2 are recommended for sheet radiant barriers because dust will accumulate on the radiant barrier if it is installed at location 3. Figure 1 illustrates the locations in which a radiant barrier may be installed in an attic. A radiant barrier is typically a layer of reflective aluminum foil material placed in the attic next to an air space to block radiant heat transfer between a heat-radiating surface (such as the underside of the roof deck) and a heat-absorbing surface (such as insulation at the attic floor).
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