Thermal Performance of Low Emittance Building Sheathing

Abstract

Large (3 by 4 m) residential building wall specimens were tested in a calibrated hot box to measure the thermal performance of vertical air spaces formed by siding and sheathing. Test results reveal that the irregular air space formed by beveled siding applied directly over sheathing does not significantly reduce wall heat transfer regardless of effective space emittance. On the other hand, plywood siding applied to sheathing over furring strips to form 19 mm (3/4") plane air spaces having effective emittances of 0.03'and 0.73, produced space thermal resistances (R-values) of 2.45 and 0.89 h-ft ². F/Btu, respectively, at 5° C (40° F) wall mean emperature. These lower-than-tabulated ASHRAE R-values are attri buted to typical siding/sheathing system variables such as air convection and leakage.