This document provides the product category rules (PCR) for Type III environmental declarations (as in EN 15804:2012+A2:2019 1) for factory made and in situ thermal insulation products. Complementary to EN 15804:2012+A2:2019 1, the PCR described in this document: specify the declared unit to be used; define the system boundaries for thermal insulation products; specify/describe the default scenarios and rules for defining scenarios for certain life cycle information modules. These PCR are intended to be used for cradle to gate, cradle to gate with options or cradle to grave assessment, provided the intention is properly stated in the system boundary description.