Attic expansion with 20mm insulation between drywall panels, mold

Hello everyone,

I am currently in the process of converting our attic, built in 1979, into living space.

So far, I have done the following:

Insulation between rafters with Thermolan Unifit 035 140mm, then reinforced with 60mm squared timber and TP-KD 035 60 mm core insulation boards in between. Then a vapor barrier foil.

Now I am installing the battens for the plasterboard, and I have the following question/idea:

Is it sensible to fill the resulting cavity with 20mm insulation as well, following the idea that more is better, or is that money wasted, or maybe even a fatal error because this insulation would then be in front of the vapor barrier foil and not behind it, potentially causing moisture damage such as mold?

Thank you in advance for reading and responding.

Kind regards Migo

....Is it sensible to fill the resulting gap with 20mm insulation as well, following the motto "more is better," or is that money thrown away, or perhaps even a fatal error, ...

That should be determined beforehand. How much insulation makes economic sense or is necessary so that the additional heating load can still be provided by the existing heat generator. One should also consider beforehand whether the existing hydraulics are sufficient ;-)

best regards