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
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.
