Georgia replaced the IECC number
Georgia adopted the 2015 IECC with its own amendments, and the blower-door requirement is where the amended figure differs most from the model code. Under the Georgia-amended 2015 IECC R402.4.1.2, a new one- or two-family dwelling in Climate Zones 2, 3 and 4 must test at an air leakage rate of less than 5 ACH50: less than 5 air changes per hour at a test pressure of 50 pascals.
The traps on the number
- 3 ACH50 is the unamended 2015 IECC figure for zones 3 to 8. Georgia replaced it, and quoting it is the listed common error.
- The wording is less than 5. A house testing at exactly 5.0 ACH50 fails. Reading it as "5 or less" misstates the rule.
- Climate Zone 4 gets no looser allowance. There is no 7 ACH50 figure; the same less-than-5 applies in zones 2, 3 and 4.
- The test pressure is 50 pascals, not 25.
Who runs the test
The amendment requires the test to be conducted by a certified duct and envelope tightness (DET) verifier. The verifier gives the signed written report to the code official.
- The building official receives the report; the official does not run the test.
- The builder is not named as the tester.
- An HVAC licence alone is not the certification the amendment requires.
Accepted test standards
R402.4.1.2 as amended lists three test methods:
- ASTM E779
- ASTM E1827
- ANSI/RESNET/ICC 380
ASTM E119 is not on the list. Expect a question that names three of these methods plus one outsider and asks which is not accepted; E119 is the outsider.
Putting it together
For any new Georgia house in zones 2 through 4: a DET verifier tests it under E779, E1827 or RESNET/ICC 380, the result must come in under 5 ACH50 at 50 Pa, and the signed report goes to the code official. If you see 3 ACH50 in an answer, it came from the unamended model code, not from Georgia's amendment.