What blower-door air leakage rate does code require for a new house?
Tested envelope leakage must not exceed 5 ACH50 in zones 1-2 and 3 ACH50 in zones 3-8 (IRC N1102.4.1.2).
The IRC requires the building thermal envelope of a new home to be tested for air leakage with a blower door. The measured rate cannot exceed 5 air changes per hour at 50 pascals (ACH50) in climate zones 1 and 2, or 3 ACH50 in climate zones 3 through 8.
The test is run at a 50 Pa pressure difference with a calibrated blower door, and the result is documented for the building inspector. Tighter is better for energy use, but very tight homes typically pair the air sealing with mechanical ventilation.
Both the 2012 and 2015 IRC use the same section (N1102.4.1.2) and the same 5/3 ACH50 thresholds. The code also lists the specific air-sealing details that must be completed before the test.
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Adopted edition and local amendments vary by city and county. Ask Donnie checks your jurisdiction and cites the exact adopted section.
Ask Donnie →General information based on the International Residential Code (a model code). This is AI assistance to verify — not legal advice. Confirm the adopted edition and any local amendments with your local building department (AHJ) and a licensed professional before you build.