The paper describes the main results from a research project performed by "The Mobile Laboratory of Indoor Climate Measurements" one of the five mobile laboratories of the Institute. The aim of the project was to investigate if undesirable consequences occurred in the indoor climate when using an energy saving method consisting of reducing the mechanical exhaust from the "wet rooms" to app. 40 per cent of the normal performance during 12 hours of day and night. The paper describes the selection of dwellings for the investigation, measuring methods and instruments, and the increase in indoor air humudity by using the reduction in ventilating mentioned. The conclusion is that in those 3 buildings from the investigation increases in the relative humidities were stated in a third of the dissipations on the 360 humidity measurings which formed a part of the investigation. The highest air humidities were measured in bedrooms. Therefore, there is no reason to believe that the energy saving method should cause any health risks in the 3 buildings from the investigation.