Why use battens and counter battens instead of just OSB and then gypsum?
Two layers of battens were a misunderstanding. That would only have been to create the necessary installation depth for ceiling spotlights. But those only exist in the bathrooms, not in the bedrooms.
So insulation between the collar beams, one layer of battens, and then directly drywall will probably be the solution.
The ventilation unit is completely decoupled within the casing itself and will not be placed on the floor, but either hung on the gable wall or on a frame.
The hot water tank and boiler have already been installed in the attic. In the meantime, we have started on the sloped ceilings upstairs. It will be:
- 200 mm rock wool
- vapor barrier
- 80 mm combined board of insulation and wood fiber
- drywall
So about 9 cm will be added below the rafters. Then you can immediately fill and paint.