Retrofitting lines (LAN, COAX, etc.) in OKAL wooden prefab house

So with my first house, which I built using timber frame construction, a vapor barrier was installed in the exterior walls AND intermediate ceilings. Not in the interior walls. The year of construction was 2001. If I were you, I would first get informed about that. Interior wall structure as in your case: plaster -> drywall panel -> chipboard -> insulation -> chipboard -> drywall panel -> plaster. Intermediate ceiling structure: floor covering -> dry screed -> chipboard -> vapor barrier -> wooden beams -> insulation wool -> PE film -> drywall panel

It also depends heavily on how the walls need to be protected. Now, in the vacant house, opening or cutting out walls (generously) and closing them with new panels was certainly work, but doable. If done properly, you won’t see it later. It would look completely different in an inhabited state. Therefore, I find the approach of very sensible. When in doubt, it's even better to open up a bit more generously if you’re going to redo the entire wall anyway.