Moisture in new buildings increases during wet weather - experiences?

Hello, I am currently living in a comparable situation. For now 3 years in a former new building without a ventilation system (also no extractor fan in the bathroom or similar). It has only been about half a year since the apartment was no longer "musty," so it was "damp" for 2 1/2 years. Quickly built in solid construction by the construction company who is also my landlord. I was usually out of the house around 7:00 am and only back 10-14 hours later. Ventilating briefly in the morning and evening did not really suffice to make the situation bearable. Additionally, there is a sluggish underfloor heating system. Now I will move out soon; apparently, almost all new buildings are constructed this way to still enable (or maximize) returns.

I am still amazed that this problem only occurs during/after wet weather(?).

Maybe it's because the humidity is generally already high in damp weather? Otherwise, it wouldn't be damp weather either :rolleyes:

Maybe it's because the humidity is generally already high in damp weather? Otherwise, it wouldn't be damp weather :rolleyes:

I get it :). But if I ventilate in the morning before a rainy day, the humidity then drops below 50%, and in the evening, with the rooms still closed, it hits 60%, only to wake up at 70% the next morning, how is the apartment supposed to have noticed anything about the weather if everything is closed? In dry weather, the humidity fluctuates around 50%. In the evening before ventilating, it may have risen by 3-4%, which I can simply balance out again. By the way, it’s also worth mentioning that when it was still dry *and* cold outside, the humidity was only an unpleasant 30%.

I am a tenant and recently moved into a newly built apartment,

What kind of building is this and what was used for construction / masonry? Wall structure? ETICS?

By the way, it should also be mentioned that when it was still dry *and* cold outside, the humidity was even at an unpleasant 30%.

That is usually strange.
The construction moisture mentioned here can therefore actually not be the cause. You don’t heat that much away in new buildings.

how is the apartment supposed to have noticed anything about the weather when everything is closed?

Because it is not an hermetically sealed room.

By the way, it should also be mentioned that when it was still dry *and* cold outside, the humidity was even only an unpleasant 30%.

So exactly like outside. You don’t have a sealed apartment and the indoor humidity adjusts to the outside.

I don't know what it was built with. It is not faced with bricks and inside there is only plaster with paint.

The fact that the humidity simply equalizes to the outside also describes the subjective feeling. But is this a problem, or a mistake, or is it allowed to be normal? Of course, I am also thinking about what will happen in summer when it gets significantly warmer again.