Duct pressure testing (or “duct leakage testing”) measures the amount of leakage in a duct system and air handler. At Eco Three, we primarily use this test in new construction homes to ensure the system meets Energy Code requirements. Before the test, we cover all registers/vents then attach our duct testing fan and manometer to a central return. Then we turn on the fan and depressurize to 25 pascals. The manometer measures the cubic feet per minute pulled through the system by the fan. The result is the number of cubic feet per minute at 25 pascals or CFM25. Duct leakage is calculated based on the square footage area that the system heats and cools. If a system exceeds the allowable leakage, we can pressurize the system and use a smoke pen to identify leaks. We can then properly seal any identified leaks in the system with mastic paste or HVAC foil tape.
On existing homes, we often run a blower door and use a pressure pan to check leakage on individual vents after we seal the systems. For new construction, we can test at rough in (pre-drywall) or post-construction (post drywall). It is generally easier to resolve leakage at rough in. For post-construction duct pressure testing the boots must be caulked or siliconed to the drywall or floor to prevent bypass leakage. If you are unfamiliar with how to properly install and seal a duct system, please call us. We enjoy teaching our HVAC clients how to improve techniques and pass duct tests.