Validating and improving the delta-Q duct leakage test

The Delta-Q duct leakage test has been developed over the past several years as an improvement to existing duct pressurization tests. It focuses on measuring the air leakage flows to outside at operating conditions that are required for energy loss calculations for duct systems, and infiltration impacts. The Delta-Q test builds on the standard envelope tightness measurement technique of a blower door by repeating the tests with the system air handler off and on. This study uses detailed
laboratory measurements to validate the Delta-Q test procedure and calculations. The laboratory measurements used a purpose-built test chamber coupled to a duct system typical of forced-air systems in U.S. homes. Special duct leaks with controlled and monitored airflow were designed and installed in the duct system. This test system enabled us to systematically vary the duct and envelope leakage and to accurately measure the duct leakage flows for comparison to Delta-Q test results. The laboratory testing has also led to enhancements to the Delta-Q calculations that increase the accuracy of the leakage measurement.