In buildings, favorable growing conditions for mold fungi can occur and cause fungusinfestation. The danger for the occupants of dwellings lies in the spreading of pathogensthrough microorganisms. Mold fungi can occur not only on the surface of external walls, butalso inside construction parts. A prerequisite for preventing mold fungus is the knowledge ofthe transient building physical boundary conditions under which fungus growth takes place.The decisive parameters of influence like temperature, humidity and substrate have to beavailable over a certain period of time simultaneously.