Although somewhat controversial for industrial applications, radiant barriers have won widespread acceptance in the residential building industry. A thin film of reflective foil spread under the roofing materials forms a barrier to solar radiation impacting the roof. The radiant barrier reflects the radiation before it can enter the living space and be transformed into heat as it is absorbed by the building structure and the furnishings within.
The industry has tried unsuccessfully to quantify this phenomenon, to assign an R-value to radiant barriers like that given to insulation and other building materials. As a result, it’s difficult to determine the energy savings that happen in buildings equipped with radiant barriers. A conservative estimate of the increase in the R-value of the roof assembly provided from radiant barriers is 15 to 20 percent.