A vapour retarder is defined as a material or system which adequately retards the transmission of water vapour. This fact sheet from the North American Insulation Manufacturers Association (NAIMA) gives important information as to when and where vapour retarders should be used.

NAIMA is a trade association of North American manufacturers of fiber glass, rock wool, and slag wool insulation products. Their site provides a wealth of information on the uses and benefits of these products from thermal comfort to public health. Visit www.naima.org/ to access this resource.

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