Assessment of the thermal performance of timber walls under nominal or moisture and temperature dependent properties

Materials thermal properties are generally assumed equal to nominal values in building simulation codes, even if they depend on both temperature and moisture content. For some materials, such as timber, this hypothesis can bring inaccuracies affecting the predicted building energy performance. In this research, a MATLAB® ID heat and mass transfer model was developed according to the finite difference approach, with material thermal conductivity function of water vapour partial pressure and temperature. After calibration against laboratory experiments on spruce XLAM specimens, annual simulations were run for 110 Italian climates and specific hourly heat fluxes compared to those determined with nominal properties.