Class I and II vapor retarders shall not be provided on the interior side of frame walls in Zones 1 and 2. Class I vapor retarders shall not be provided on the interior side of frame walls in Zones 3 and 4. Class I or II vapor retarders shall be provided on the interior side of frame walls in Zones 5, 6, 7, 8 and Marine 4. The appropriate zone shall be selected in accordance with Chapter 3 [CE] of the International Energy Conservation Code-Commercial Provisions.
Exceptions:
- Basement walls.
- Below-grade portion of any wall.
- Construction where moisture or its freezing will not damage the materials.
- Conditions where Class III vapor retarders are required in Section 1405.3.2.