Bathroom ceiling moisture + inadequate insulation

Of course this is a cold roof and, judging by what can be seen in the photos, it has been executed properly.

The fact that the underlay membrane is not sealed tightly to the exhaust pipe only has an impact during severe storms with driving rain, when water is pushed under the tiles.
Likewise, insulation of the pipe is not necessary, as it is always warmer than the outside air and not colder.

Either there are serious errors here that cannot be seen in the photos, or it simply is not being ventilated, which is the cause in most cases.
If you shower hot for 10 minutes, you need to open the window fully for at least 5 minutes afterwards if you have no ventilation system. Do you do that?

We usually air out in the morning after showering for at least 10 minutes and again in the evening for another 10-15 minutes. Always cross-ventilate the entire floor. In between, the bathroom is ventilated occasionally during the day when the cats have used the litter box and it smells. Of course, one could air out crosswise again at noon, but that should actually be sufficient. Possibly the moisture has been in there for a longer time. I know that after the screed was installed, ventilation was sometimes insufficient. Unfortunately, we had no influence on that.

With me, the entire underlay was also full of water droplets. However, this was during and after the screed heating. How long ago was that for you? My suspicion is that the ceiling was simply closed too early. Have you discovered any mold on the roof beams anywhere?

The screed was installed in June but dried without a heating program. The heating program ran at the end of August / beginning of September.

In the attic, I felt a draft, so ventilation is definitely present. No idea if the moisture can stay inside for that long (since the screed). Possibly there is not enough ventilation.

We will definitely have access to the attic created so that we can monitor it in the future.

For 100% certainty, I would place a data logger with rH sensor at the top for one week. Then you can see if the humidity rises after showering. If not, then it is residual moisture.

Ok thanks for the tip

ps: I did not discover mold on the roof beams