Determine which energy-code air-leakage and air-barrier compliance path applies to a commercial building's envelope

Steps

1. Identify the IECC edition adopted by the project's jurisdiction, since the air-leakage/air-barrier section number differs by edition: it is Section C402.5 in the 2021 IECC and earlier editions, and was renumbered to Section C402.6 in the 2024 IECC (with fenestration provisions moved into the 2024 edition's C402.5)
2. Confirm the compliance path: either meet the prescriptive air-barrier material/assembly/design requirements in the applicable subsections, or test the whole building per ASTM E779 (or the large/multizone equivalent) and demonstrate a measured leakage rate at or below the code's threshold
3. Verify the current numeric threshold for the adopted edition rather than assuming a fixed value — thresholds have tightened across cycles (e.g., 2024 IECC increased stringency versus prior editions for several occupancy categories) and vary by occupancy group and climate zone
4. Confirm material-level deemed-to-comply air-permeance thresholds reference ASTM E2178 testing, and assembly-level thresholds reference ASTM E2357 (or code-listed alternates such as E1677/E283) for the adopted edition
5. Confirm whole-building compliance testing must be performed by an approved third party, as required by the code text
6. Check whether the adopted edition requires air-barrier location, sealing details, and identified thermal bridges to be shown on construction documents (a documentation requirement added in more recent IECC cycles)