Presents the results of laboratory measurements of the thermal performance of clean horizontal radiant barriers in a simulated residential attic module under night time or low solar gain daytime winter conditions. Comparing tests under the same conditions with and without a radiant barrier shows that the addition of a clean horizontal radiant barrier to insulation at the R22 to R25 level decreases the ceiling heat flow by 6% to 8%. The experimental results were found to be in very good agreement with predictions made with a mathematical model for the thermal performance of attics. Note R22 = surface to surface thermal resistance 22 h-ft.2 deg.F/Btu.

KEYWORDS: thermal insulation, attics, experiment, radiation, radiation control coatings, measuring, calculating, models, winter, laboratory testing, horizontal.