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Duct Tightness Testing
Duct Test Timing: Construction Phase

Duct tests for DET Verification can occur anytime after the air distribution portion of the heating and cooling system is installed, typically the pre-drywall phase, and before the final phase inspection leading to a certificate of occupancy.

Pre-Drywall Duct Tests

Until the methods of sealing ductwork are routine, it’s best to have the duct leakage tested before drywall is installed.  Besides the advantage of being able to fix the leaks more easily, passing the pre-drywall test is best for everyone because the success criterion is tighter.

The major reason for first-time duct test failure is removed because there are no grilles or diffusers for air to be reflected back through holes in walls, floors, and ceilings.  The register boots are directly covered with tape.

Final Duct Tests

Duct tests can also be done when the house is finished.  There are two advantages.  First, there is only one trip when blower door testing is also required.  If it turns out the total leakage test fails, there is and opportunity to pass the duct leakage-to-outside test.  The procedure involves setting up the blower door.


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