scope:

This European Standard gives the method of calculation, based on one-dimensional heat flow, of the thermal transmittance of building components and building elements, excluding doors, windows and other glazed units and components which involve heat transfer to the ground. The calculation method is based on the appropriate design thermal conductivities or design thermal resistance of the materials and products involved. The method applies to components and elements consisting of thermally homogeneous layers (which can include air layers). The standard also gives an approximate method that can be used for many types of inhomogeneous layers, together with consideration of the maximum error of the approximation. Methods are given for calculation of the thermal transmittance of building elements when there is an unheated space between the internal and external environments.