Assessing the longevity of residential duct sealants

Duct leakage has been identified as a major source of energy loss in residential buildings. Most duct leakage occurs at the connections to registers, plenums or branches in the duct system. At each of these connections a method of sealing the duct system is required. Typical sealing methods include tapes or mastics applied around the joints in the system. Field examinations (both physical measurements and visual observations) of duct systems have shown that these seals tend to fail over extended periods of time. In this study, three test methods were used to test the longevity of duct sealants: simple heating, heat cycling and combined pressure and heat cycling (aging). The most advanced method was the "aging" test, developed to evaluate the longevity of duct sealants by alternatively blowing hot (75°C) and cold (-5°C) air through test sections, with the apparatus cycling between hot and cold air quickly. The temperatures and cycle length were chosen to accelerate the aging process of the duct seals. The aging apparatus was able to test eight samples at a time, with the test samples constructed from standard duct fittings. The results of these tests were used to evaluate different sealants relative to each other, so that recommendations regarding duct sealants may be developed. Typical duct tape (i.e. fabric backed tapes with rubber adhesive) was found to fail more rapidly than all other duct sealants. The accelerated test method is being developed into an ASTM Standard under sub-committee E6.41.