ABSTRACT

The word 'moisture' relates to water in its three states that is vapour, liquid and solid with inclusion of all substances, such as salts, dissolved in it. Moisture is responsible for 70 to 80% of all damage in buildings. Thus, correct moisture control is a prerequisite for getting sustainable buildings. Several driving forces cause moisture to move in and through open-porous materials. Looking to the vapour phase, two intervene: diffusion and bulk transport. Moisture modelling is never an activity on its own. As temperature and air pressure differences act as driving forces, one always has to combine with heat and air transport, the whole being called hygrothermal modelling. Solving a combined heat, air and moisture problem demands knowledge of the exact geometry of a building assembly, together with the starting conditions, the exterior and interior boundary conditions and the contact conditions between material layers.