Stone wool insulation will not expand or contract due to temperature variances within the enclosure. These attributes result in optimal thermal performance of a building envelope. Vapour Permeability Insulation products, membranes and other building materials all have varying levels of vapour permeability and can potentially act as a vapour retarder. When designing enclosures with thick insulation levels, consideration with regards to the appropriate use of vapour retarders is critical. Depending on the climate location of the building, the vapour retarder profile should be either on the interior or exterior side of the enclosure.