The housebuilding standard is changing rapidly due to the Ecodesign directive because the use of energy is more and more limited. Less energy consumption can be achieved step by step with tighter and better insulated houses. These new houses causes a change of living as well. New houses demands new responsibilities, for instance to ventilate. It is not easy for people to get used to this! The result of poor ventilation is bad indoor air quality and very often high humidity.
The safest way to ensure right ventilation is to install a residential ventilation system that extracts used air, odor, exhalations from furniture, paints, etc. and humidity in wet rooms like bathrooms or kitchens.
At cold outdoor temperatures the outside air has a low water content and during heating it up the relative humidity (RH) will decrease rapidly (outside air at -10°C and RH of 90%, warming up to 20°C the RH decreases down to 10%!). Mixing constantly dry supply air with indoor air in wintertime the indoor air humidity can go down to an uncomfortable and unhealthy level. It is not unusual to have RH indoors of 20% or even lower which is much too low.