Water vapor transport to material surfaces-Simplified analytical expressions for non-linear material properties

Abstract

The water vapour transfer between the indoor air and material surfaces is of importance for the moisture balance of the room. It can also be important for the moisture content and durability of the material surface layer such as artefacts in churches and historical buildings. For most building materials the penetration depth due to short time fluctuations, such as diurnal ones, is very limited. For these cases the assumption of semi-infinite analysis gives accurate results even for a rather thin material layer. In the paper, the moisture profile and surface moisture uptake are modelled in detail for isothermal cases and strongly non-linear material properties for the sorption isotherm and vapor permeability. An approximative formula is given for a quite accurate estimate of the moisture up take for a demonstration case with a strongly non-linear material.