scope:

Specifies equipment and procedures for determining the water vapour transmission rate, water vapour permeance and water vapour permeability in the steady state under different sets of specified test conditions of test specimens. It is applicable to thermal insulating products. It is designed for homogeneous materials and for products which may contain integral skins or adhered facings of some different material. The results obtained by this method are suitable for design purposes, production control and for inclusion in product specifications. The water vapour transmission rate and permeance values are specific to the specimen (i.e. the product) thickness tested. For homogeneous products, the water vapour permeability is a property of the material.