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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 other than Marine 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:
  1. Basement walls.
  2. Below-grade portion of any wall.
  3. Construction where moisture or its freezing will not damage the materials.
  4. Conditions where Class III vapor retarders are required in Section 1404.3.2.

Related Code Sections

1404.3.1 Exterior Walls, Class I and II Vapor Retarders
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