Both the 2009 and 2012 IECC require duct tightness to be verified. Verification can take place via either a post-construction test or a rough-in test.
For the post-construction test, leakage measurement must be made across the entire system, including the manufacturer’s air handler enclosure, with all register boots taped or sealed at a test pressure of 0.1 inches w.g. (25 Pa). The 2009 IECC limits the leakage to outdoors to less than or equal to 8 cfm per 100 ft2 of conditioned floor area or total leakage less than or equal to 12 cfm per 100 ft2 of conditioned floor area. The 2012 IECC only contains a requirement for total leakage of less than or equal to 4 cfm per 100 ft2 of conditioned floor area.
For the rough-in test, leakage measurement is made across the system, with the manufacturer’s air handler enclosure if it is installed. The test is conducted at 0.1 inches w.g. (25 Pa) with all registers taped or sealed. The 2009 IECC limits leakage to less than or equal to 6 cfm per 100 ft2 of conditioned floor area when the air handler is installed and 4 cfm when it is not installed. The 2012 IECC limits the leakage to 4 cfm per 100 ft2 of conditioned floor area when the air handler is installed and 3 cfm when it is not installed.