ᐅ Attic Conversion with 20 cm Insulation between Drywall Panels, Mold Issues

Hello everyone,

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

So far, I have done the following:

Installed insulation between the rafters using Thermolan Unifit 035, 140 mm (5.5 inches) thick,
then added 60 mm (2.4 inches) squared timber on top, and placed TP-KD 035 core insulation boards, 60 mm (2.4 inches) thick, in between.
After that, a vapor barrier foil.

Now I am installing the battens for the drywall panels, and I had the following question/idea:

Would it make sense to also fill the cavity created by the battens with 20 mm (0.8 inches) insulation, following the “more is better” approach? Or would that be a waste of money, or perhaps even a serious mistake, since this insulation would be located in front of the vapor barrier instead of behind it, potentially causing moisture problems such as mold?

Thank you in advance for reading and answering.

Best regards,
Migo

Migo schrieb:
....Is it reasonable to also fill the resulting gap with 20mm (0.8 inch) insulation, following the idea that more is better, or is that just wasted money, or maybe even a critical mistake,
...

This should be determined beforehand. How much insulation makes economic sense or is necessary for the existing heating system to still cover the additional heating demand. You should also consider beforehand whether the current hydraulics are sufficient ;-)

Best regards