This document specifies common evaluation rules useful for the assessment and verification of constancy of performance of a thermal insulation product with harmonised technical specifications, product standards and any other assessment documents. Harmonised technical specifications, product standards and other assessment documents are called European product specifications in this document. This document applies to factory made products for buildings, factory made products for building equipment and industrial installations, in situ products for buildings, in situ products for building equipment and industrial installations, to products for civil engineering applications, and to external thermal insulation composite kits.