Scope

• Bitumen, plastic and rubber sheets for roof waterproofing;
• Thermal insulating products for building applications.

Standards

• EN 1931 - Flexible sheets for waterproofing - Bitumen, plastic and rubber sheets for roof waterproofing - Determination of water vapour transmission properties
• EN 12086 - Thermal insulating products for building applications - Determination of water vapour transmission properties

Principle

The test specimen is sealed to the open side of a test dish containing a desiccant. The assembly is then placed in a test atmosphere whose temperature and humidity are controlled. Because of the difference between the partial water vapour pressures in the test assembly and in the test atmosphere water vapour flows through the test specimen. Periodic weighings of the assembly are conducted to determine the rate of water vapour transmission when the steady state is reached.