ᐅ High Humidity in the Bathroom: What Could Be the Cause?

Hello everyone!

Since moving into my own house, I have had a constant problem with humidity in the bathroom. It is always too damp, not just after washing or showering, but all the time. The towels don’t dry properly, and mold forms occasionally on the walls.
The bathroom shares a wall with the garage, which is made of Ytong blocks (20cm (8 inches) thick). The other walls are made of 24cm (9.5 inches) bricks.
Ceiling structure: bitumen roofing felt, 30cm (12 inches) insulation, vapor barrier, wooden panels.
The bathroom has a window and is of course regularly ventilated, but I just can’t get the average humidity down.
I’m really at a loss—what could be causing this?

Since you regularly ventilate, yet the bathroom still does not dry, there is a risk that moisture is entering the bathroom from outside.
I cannot say where it might be coming from, as I am not familiar with your house.
Possible causes could be leaks (roof, water pipes, bathtub drain, joint between bathroom wall and garage, etc.).
You should consult a professional or expert who can investigate the situation with a moisture meter or similar equipment.

Unfortunately, it is really difficult to determine where the moisture is coming from! Is the moisture consistently present even when the windows remain closed? If so, something must have definitely gone wrong during the construction!