prEN 12939

Thermal performance of building materials and products - Determination of thermal resistance by means of guarded hot plate and heat flow meter methods - Thick products of high and medium thermal resistance

Publication date:   Oct 16, 2025

Scope

This document specifies procedures to determine the thermal resistance of products whose thicknesses exceed the maximum thickness for guarded hot plate or heat flow meter apparatus. Most of the procedures described in this standard require apparatus that allows tests on specimens up to 100 mm thick .
This document gives guidelines to assess the relevance of the thickness effect, i.e. to establish whether the thermal resistance of a thick product can or cannot be calculated as the sum of the thermal resistances of slices cut from the product, these guidelines complement the indications given in ISO 8302:1991[1] on the guarded hot plate apparatus.
This document describes testing conditions which prevent the onset of convection which could take place in some products under the considered temperature differences and thicknesses.