Spontaneous renovation of extension.

[Xellvas]

Hello!

I have an extension on the house that has been looking a bit dull, so I decided to check under the surface.
It turned out that someone had previously repaired water damage by nailing fresh wood onto the rotten parts, even insulating between the decayed and new breather membrane in the roof, splicing fully rotten rafters, and some other things.
Now I am forced to tear down at least 3.5 of the 7-meter plank wall and build a new wall.
My plan is to build a new 120mm stud frame with a 45mm installation layer and attach it to the remaining plank wall.
Or should I take down the entire wall and build a 7-meter 145mm + 45mm? I don't plan to use plastic but a vapor barrier, so I don't dare to insulate too thickly.

Best regards

 

[Xellvas]

Anyone have any advice regarding 145mm mineral and only vapor brake? Cellulosan is insanely expensive. But if it's risky, well, it's just about biting the bullet. I've at least decided to tear down the last part of the plank wall next weekend, it will probably lead to a better end result.