Determine when an air curtain can substitute for a vestibule at a commercial service door under the IECC, and how that interacts with loading-dock exemptions.

Steps

1. Check whether the door in question is a loading-dock/material-handling type door — the IECC's vestibule requirement generally already exempts doors primarily used for vehicle or material movement (and adjacent personnel doors) at loading docks, so no air-curtain substitution is needed there.
2. For other commercial service/entrance doors that would otherwise need a vestibule, confirm the air curtain meets the IECC's performance threshold — commonly stated as air velocity of not less than about 6.56 ft/s (2 m/s) at 6 inches above the floor.
3. Verify the air curtain unit has been tested to the referenced rating method (ANSI/AMCA 220 or ISO 27327-1, depending on IECC edition) rather than relying on an untested manufacturer velocity claim.
4. Confirm the air curtain is installed per the manufacturer's instructions and is controlled to operate automatically with the door's opening and closing.
5. Identify the exact IECC section number and edition adopted locally before citing it in documentation, since the vestibule/air-curtain section number has moved between editions (e.g., different C402.5.x numbering across IECC 2018/2021).