This standard gives calculation methods for: a) The internal surface temperature of a building component or building element below which mould growth is likely, given the internal temperature and relative humidity - the method can also be used to assess the risk of other surface condensation problems. b) The assessment of the risk of interstitial condensation due to water vapour diffusion. The method used assumes built-in water has dried out and does not take account of a number of important physical phenomena including: - the dependence of thermal conductivity on moisture content; - the release and absorption of latent heat; - the variation of material properties with moisture content; - capillary suction and liquid moisture transfer within materials; - air movement through cracks or within spaces; - the hygroscopic moisture capacity of materials.