Effects of Radiant Barrier Systems on Ventilated Attics in a Hot and Humid Climate

Results of side-by-side radiant barrier experiments using two identical 144 ft2 (nominal) test houses are presented. The test houses responded very similarly to weather variations prior to the retrofit. The temperatures of the test houses were controlled to within 0.3°F. Ceiling heat fluxes were within 2 percent for each house. The results showed that a critical attic ventilation flow rate (0.25 CFM/ft2 ) existed after which the percentage reduction produced by the radiant barrier systems was not sensitive to increased airflows. The ceiling heat flux reductions produced by the radiant barrier systems were between 25 and 34 percent, with 28 percent being the reduction observed most often in the presence of attic ventilation. All results presented in this paper were for attics with R-19 unfaced fiberglass insulation and for a perforated radiant barrier with low emissivities on both sides