Types of Vapor Retarders


Any material that has a rating of 1 perm or less is considered to be a vapor retarder. The table below shows the perm rating of some common building materials that are consistent with ASHRAE Handbook of Fundamentals and other industry sources.

Vapor Retarders Permeance1
Kraft thermal insulation facing (asphalt laminated) 12
Foil thermal insulation facing
0.52
Saturated and coated rolled roofing
0.05
Paint (2 coats)
0.3 to 3 4
Polyamid, 2 mil (variable permeability membrane)
1 to 202
Polyethylene, 4 mil
0.08
Polyethylene, 6 mil
0.06
Vapor retarder paint (1 coat)
0.6 to 0.93
Not Vapor Retarders
Perm Rating
Olefin, spunbond high density fiber (housewrap)
942
Plaster (3/4" thick) on wood lath
115
Gypsum wall board (3/8")
506
Notes:
  1. Values from 2009 ASHRAE Fundamentals handbook,unless otherwise noted.
  2. Value supplied by manufacturer.
  3. Value from Rodale Products Testing Laboratory.
  4. Perm ratings for specific paints should be verified by independent testing using ASTM E-96A or equivalent TAPPI test standards.
  5. Wet cup method.
  6. Other than wet or dry cup method.

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