The Delta Q method of testing the air leakage of ducts

Publication Type

Conference Paper

Date Published


LBNL Report Number



The DeltaQ test has been developed in order to provide better estimates of forced air system air leakage for use in energy efficiency calculations and for compliance testing of duct systems. The DeltaQ test combines a model of the house and duct system with the results of house pressurization tests with the air handler on and off to determine the duct leakage air flows to outside conditioned space at operating conditions. The key advantage of the DeltaQ test over other methods is that it determines the air leakage flows directly, rather than requiring interpretation of indirect measurements. The results from over 200 field and laboratory tests are presented. The laboratory tests have shown that the DeltaQ repeatability uncertainties are typically 1% or less of system fan flow and that the accuracy of the test is between 1.3% and 2.5% of fan flow (or 13 cfm to 25 cfm (6 to 12 l/s) for this system).

Conference Name

Proceedings of the ACEEE Summer Study on Energy Efficiency in Buildings, August 18-23, 2002

Year of Publication



American Council for an Energy Efficient Economy, Washington, DC

Conference Location

Pacific Grove, CA