diffusion tight!

[Lcms]

I wonder if anyone knows if wet room paint/aluminum foil that was used on walls in the past is diffusion tight/Lars

 

[KnockOnWood]

I also had paper with aluminum foil in some walls in the house before last.
It is definitely diffusion-tight.

I think it was later banned for safety reasons.
A nail into the foil that goes into an electrical wire potentially makes the whole wall live.