This document describes a set of procedures for using existing standardized CEN or ISO test and calculation methods to determine the thermal performance of reflective insulation products. This document supports and does not replace existing CEN or ISO test methods. This document applies to any thermal insulation product that derives a proportion of its claimed thermal properties from the presence of one or more reflective or low emissivity surfaces together with any associated airspace(s). It does not replace the existing procedures for the determination of the thermal performance of products already covered by an existing harmonized product standard where the declared value of these products does not specifically include any claims attributable to the emissivity of the facing. It does not, and cannot, give an in-use or design value of thermal performance, but provides standardized information from which these can be determined.