A Field Comparison of the Delta-Q Test for Duct Leakage to Other Test Methods

Two studies have recently been performed to evaluate the current form of the Delta-Q test for duct leakage. In the first study 19 new homes in Wisconsin, USA were tested, and in the other 14 existing homes in Central Illinois, USA were measured. A primary goal was to determine whether the Delta-Q test was sufficiently reliable to use in production programs such as weatherization and home energy ratings, which currently use primarily the pressure pan or duct pressurization tests, respectively. Delta-Q has the potential to provide better estimates of actual leakage under normal operation, and is an attractive alternative if it provides at least as reliable a signal regarding whether repair of the ducts is warranted. The results showed that the Delta-Q test provides leakage estimates that are 20% higher than those from the nulling test, though the 95% confidence intervals for the two tests overlap in most cases. The data show that the median of the individual register pressure pan measurements correlates well with the Delta-Q test. There were a few cases where the duct pressurization test produced a false positive reading, and thus suggested that air sealing should be done when in fact there was not large leakage.