This paper presents a new method for estimating duct leakage in residential homes. This method, called the nulling test, does not require assumptions of the leakage characteristics of the house or the ducts. It measures leakage to the outside and does so at operating conditions. This provides the leakage parameter that is necessary for estimating thermal distribution system efficiency. This paper describes the nulling test in detail, including both the theory and how to perform the test. Advantages and disadvantages of the nulling test are discussed and compared to those of other tests that have been used in the past. Following these discussions, the results of several field tests of the nulling tests are presented and compared with those of other tests.

Units: I-P