Cooling season energy measurements of dust and ventilation effects on radiant barriers

Abstract

Cooling season tests were conducted in three unoccupied ranch-style houses in Karns, Tennessee, to determine the effects on attic radiant barrier performance incurred by changes in attic ventilation area ratio, attic ventilation type, and the buildup of dust on horizontal radiant barriers. All three houses had R-19 fiberglass batt insulation in their attics. Horizontal radiant barriers were artificially dusted and the dusted barriers showed measurable performance degradations, although the dusted barriers were still superior to no radiant barriers. Dust loadings of 0.34 and 0.74 mg/cm{sup 2} reduced a clean radiant barrier surface emissivity of 0.055 to 0.125 and 0.185, respectively. Total house cooling load increases amounted to 2.3 and 8.4% compared to house loads with clean horizontal barriers, respectively. When compared to R-19 with no horizontal radiant barrier conditions, the dusted horizontal radiant barriers reduced cooling loads by about 7%. Testing showed that increasing the attic ventilation area ratio from the minimum recommended of 1/300 (1 ft{sup 2} of effective ventilation area per 300 ft{sup 2} of attic area) to 1/150 had little if any effect on the house cooling load with either truss or horizontal barriers present in the attics. Radiant barriers, however, still reduced the house cooling load.more » 18 refs., 17 figs., 26 tabs.« less