I am trying to model a roof like the one in the attached picture. It is slightly different than those in the wizard. Ideally it should feature a thermal zone above living spaces, separated by just a gypsum plasterboard false ceiling. The overhangs could be modelled as shading devices in separate zones.
The problem is, the house has different false ceiling heights, for example in bathrooms and living rooms, as in roof2.jpg (also attached). As far as I know, the false ceiling planes should be "parents" in the roof zone, but I cannot manage to do it like that...

If anyone has solved this problem, has a different valid approach, or any useful tip, I'd be most grateful.