Iain Walker and Max Sherman developed the DeltaQ test in 2002 to provide a more accurate measurement of duct leakage. The test is relatively easy to perform, and it uses less time, less equipment, and less labor than the existing tests.
As they write in the September/October, 2002 issue of Home Energy, "For many years, building scientists have known that information on duct leakage can be obtained using blower door tests that include the duct system. However, most efforts have focused on using a single test pressure and some assumptions about converting measured air leakage flow to actual leakage at operating conditions.The DeltaQ test takes a different approach. It measures air leakage flows for the ducts and the building envelope over a large range of pressures, just as normal blower door testing does.
We call it DeltaQ because “Q” is the common term used for air flow, and “delta” is the common term used for differences. The test is based on measuring the change in flow through duct leaks as the pressure across those leaks is changed by turning the HVAC system air handler on and off." Read on...