The main process of the macroscopic modelling is presented. The modelling is based on heat and moisture balance in the process of moisture migration. The migration of moisture in a porous material is usually due to the gradients of moisture content and temperature. So the moisture existing in a certain cell migrates to the surrounding cells according to the difference of moisture content and temperature. In this simulation we suppose that there is no chemical reaction which occurs in this migration process and the local moisture content is determined by the sorption isotherm of the material as defined by equation (3). If the migration in at least one direction can be neglected, the moisture content change of the cell in a unit time is determined by the diffusion of moisture in two directions as shown in equation (1). The moisture migration is coupled with heat transfer and the temperature change of the cell in a unit time is determined by heat loss or gain due to heat conductance and potential heat in migrated water as shown in equation (2).