Bathroom ceiling moisture + inadequate insulation

forgot the "" or alternatively irony: On at klitzeklein ;)

Update: The drywall installer was here and insulated the pipe. Since we had a big ladder now, I was able to take a look at the entire attic. It was noticeable that the underlay membrane is wet everywhere or there is condensation. Is that normal? I thought a cold roof is cold but dry. The drywall installer said that's normal, everyone here in the new development has that... but I don't really believe it

If the cold roof lacks ventilation, that is normal, but it should not be missing. Not controlled residential ventilation, but simply air movement through planned holes.

.... That looks to me more like a systematic error. Only at this point was the pipe "forgotten" to be sealed? I never believe that in my life. If it was not done here, it was not done anywhere in the house.

I quote myself ...

I would conscientiously take the tip about ventilation to heart if I were you, especially without [Kontrollierte-Wohnraumlüftung]. That means even if it is -10 degrees, you should air out the place several times a day with short bursts, otherwise you won't be able to live there mold-free for long.

I felt a draft above but maybe not enough