Our investigations have shown that it is possible to model a complex problem using relatively simple tools. It was not possible to conduct detailed measurements to confirm the model but the obtained findings correspond to the small number of measurement results. Outdoor temperature influences the regulated volume flows on the different floors to various extent depending on the outdoor temperature. This influence cannot be prevented through static regulating methods. In the surveyed building the gravitational impact stays within the permissible limits but a network of different geometric characteristics can have a perceivable impact on the comfort of homes. The situation is the same as regards the wind. The extensive increase of air-permeability of windows means that an unregulated exhaust system becomes regulated – while ventilation volume flows considerably decrease. If windows are replaced at different time periods flats with the windows already replaced will have a much lower ventilation volume flow and the associated problems of comfort, while in the flats where the windows have not been replaced yet a significant increase will be observed in both the ventilation volume flow and the heating costs – as it has happened in the block of flats in Budapest that provided the starting point for the modelling.