Water Vapor Permeability Tests

Maximizing the comfort and function of outdoor and active wear

Water-vapor permeability is also known as the water-vapor transmission rate (WVTR). It indicates breathable performance of textiles, and is a measure of the passage of water vapor through materials. Proper selection and manufacture of materials with high water-vapor permeability can assure comfort for the wearer, especially during outdoor activities.  

Water-vapor permeability can be verified by testing the water-vapor transmission through a unit of area under specified conditions of temperature and humidity. Intertek provides a full range of water-vapor permeability tests to help apparel manufacturers improve product quality.

 

Permeable Cup Method

Permeable Cup is the method normally used to test water-vapor permeability. Water-vapor permeability is calculated after testing the water-vapor transmission rate of the specimen under specified temperatures and relative humidity. The test can be carried out into two ways* based on the same testing principle: Desiccant Method in which water vapor transmits into the test dish, and Water Method in which water vapor transmits out of the test dish.

Test Scope:

  • Fabrics 
  • Fabrics with coating or finishing
  • Fabrics with microporous membrane
  • Fabrics with hydrophobic membrane
  • Other multi-layer fabric composite sheets

Test Method:

  • ASTM E 96 Water Method & Desiccant Method
  • JIS L 1099 Water Method & CaCl2 Method & Potassium Acetate Method
  • BS 3546, BS 3424 Part 34 Method 37, BS 7209
  • GB/T 12704
  • KS K 0594
  • CNS 12222 L 3223

* Since the environmental conditions and set-up of each method differ, results from one standard are not comparable to those of another.

 

Report:

The result is expressed in grams of water vapor per square meter of fabric per 24-hour period.

 


Sweating Guarded Hotplate Method

This method determines the water-vapor resistance of textiles by placing the specimen on the sweating hotplate, which simulates the water-vapor transfer processes through materials next to the human skin. Higher water-vapor resistance means weaker breathability.

Test Scope:

  • Fabrics
  • Films, coatings
  • Foams, leather
  • Multilayer assemblies for use in clothing, quilts, sleeping bags, upholstery, etc.

Test Methods:

  • ASTM F1868 Part B/E
  • BS EN 31092
  • ISO 11092
  • KS K ISO 11092
  • CNS 15102 L3256

Report:

  • Water-vapor resistance, in square meters Pascal per watt (m2 * Pa/W)

 

 

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