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.