The transient hygrothermal modelling to assess the thermal transmittance variation of opaque walls in the Mediterranean climate

Transmission losses in opaque components are influenced by mass transportation phenomena, the latter depending on built-in humidity level, material hygrometric properties and climatic conditions. Moreover, latent exchanges due to wetting and drying processes, promoted by rainfall, incident solar radiation, velocity and wind direction, have to be taken into account. Therefore, identical opaque components could offer different transmission losses as function of exposition and location. By means of the dynamic procedure of the EN ISO 15026 implemented in the WUFI software, the effects on the thermal losses due to the combined effect of heat and mass transport in different wall solutions, were investigated with reference to two opposite climatic conditions of the Mediterranean area. By referring to the steady U-value, results showed that deviances up to 15% were detected for walls North facing, whereas heating requirements of a reference building have showed increase of 5 - 9 %.