ABSTRACT The present essay will help the project-engineer to predetermine already at the planning stage the development of climate in shelters as a function of external and internal effects. The mathematical model developed for this purpose permits the calculation of the transient behaviour from shelter climates (temperature and humidity). It also enables the calculation for large changes, whereby all significant parameters and effects can be considered. Thereby the model remains flexible and can be used for the computation of various types of shelters. The investigation of particular conditions is also possible by expanding the system. Paying special attention to the present problem of the combined instationary heat and mass transfer through porous walls, the condensation in the walls is taken into consideration. For this complex problem an efficient solution was elaborated and enclosed into the model. There is a good correlation between the calculations and the experimental results, considering the accuracy of the measured values and the chosen material data from the tested shelters.