ASTM E96 Water Vapor Transmission

Standard: ASTM E96 Standard Test Methods for Water Vapor Transmission Rate of MaterialsASTM E96 Water Vapor Transmission Assessment

Scope: Two basic methods, the Desiccant Method and the Water Method are provided for the measurement of water vapor transmission rate (WVTR). In these tests, the desired temperature and side-to-side humidity conditions, with resultant vapor drive through the specimen, are used.


  • Water Resistive Barriers (WRB)
    • Paper
    • Plastic Films
  • Water Resistive Coatings
  • Roofing Underlayments
  • Vapor Retarders such as Spray Foam Insulation
  • Foams
  • Fiberboards
  • Gypsum
  • Plaster Products
  • Wood Products
  • Plastics

Procedure: Test Procedure: There are two methods for determining water vapor transmission rate: the desiccant method and the water method. These methods are also commonly referred to as ‘dry cup’ and ‘wet cup’ tests, respectively. Calcium chloride desiccant is used in the ‘dry cup’ method, whereas water is used in the ‘wet cup’ method. By analyzing the change in weight of the cups over time, the movement of water vapor through the test material can be determined.

See the video below for a full explanation of the ASTM E96 test procedure.

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