How and why does humidity occur in the building?
Every human being generates moisture directly and indirectly. We sweat, breathe, cook, wash, water our plants and much more. But everyone lives very individually and sometimes generates more and sometimes less moisture. Some people have pets or even aquariums. Sometimes there is a sauna or even a swimming pool in the basement. Others like to cook for a long time. All this has an effect on the humidity in the building.
What all individual behaviour patterns have in common, however, is that we produce much more humidity than we think. For example, a family of four without aquariums, swimming pools or pets and with a separate laundry room produces about 10 to 15 litres of water in the living area per day. With an aquarium and the like, it can quickly be many times that amount. Just drying laundry once can mean an additional 5 to 8 litres. This moisture must be ventilated out of the flat so that the humidity can be kept constant.
Especially in a new building, however, the air humidity can come from other sources. This can be residual building moisture, for example. Residual moisture is caused, among other things, by the fact that large amounts of cement, screed, paint or simply rain have penetrated the building during the construction phase. This is quite normal and is the case in every (new) building.
In a detached house, 15,000 to 20,000 litres of water are bound up. In an average flat, there are still about 10,000 to 15,000 litres. This moisture slowly escapes from all building components (usually distributed over the first 18 months after occupancy or completion) and thus passes into the indoor air.
If this residual building moisture now also hits the occupants of the flat, the effects add up.
So it is quite normal that very high humidity can occur, especially in the first period of a new building. This high humidity can cause mould growth or damage to the building and/or furnishings. For example, this moisture can quickly condense and run down windows or doors, or furnishings can start to mould and/or it can start to smell "musty". There are also other ways in which moisture can get into a building. However, these are usually damages (e.g. leaks or similar) that have nothing to do with normal use. In such cases, you need an expert to clarify what exactly has happened and what you need to do to repair the damage.