So in the attic peak is insulated with Isover insulation wool and above that is a foil that allows air in and out. Vapor barrier vapor retarder according to roofer.
That means you have _no_ vapor barrier between the living area and the attic?
There must be one, otherwise it's your problem. If there isn't one, moisture from the warm living space will diffuse upwards through the ceiling (even through a concrete ceiling). Then you will never really get the attic dry, no matter what you do.
We also had plastering done on the inside upstairs. The entire attic peak is insulated with a vapor barrier. Clad with drywall panels but not yet
What exactly is the roof structure? You have tiles on the outside, ventilation gap, windproof membrane, insulation (?), vapor barrier ....? No drywall panels or similar .... What did you plaster?
I can at least tell you where the moisture is coming from: Warm air can hold more moisture than cold air. If the normally moist, 22-degree warm air rises from below into the attic and cools down to 5 degrees there, the humidity can already rise to 80%. I think the following could help: - ventilate to get rid of the moisture - insulate to reduce the temperature difference - vapor barrier between below and above so that not so much moist air rises upwards
So we have the foil between the attic and the ceiling. Moisture cannot come from there. Normal roof structure with insulation, foil then drywall boards and on top the tiles. No drywall over the vapor barrier foil.
My question. Can I leave the attic permanently ventilated with our roof windows open without mold forming? This way it is permanently ventilated and I could save the controlled residential ventilation.
The moisture still comes, just more slowly. Leaving the windows open is not really an option, they are then not storm- and driving rain-proof. What about heating?