Exterior wall insulation or perimeter insulation? Change by general contractor

I do think it's okay, someone must have had a reason.

And here I believe: simply to stay under 50 cm.

I wouldn't want it, but I think technically it will be okay.

With surface-mounted installation (also cable ducts) yes.

The structural engineer simply knows better than forum users.

The structural engineer doesn't care about surface-mounted boxes, but in his own living room he prefers it nice.

My normal interior walls also need to be chased.

Oh 11ant, do you really believe he now has electrical work listed as surface-mounted in his construction service description? His imagination must be running wild. Besides, his wall construction is already in KFW40 quality. If you wanted it thinner, you could save another 4cm of insulation.

There is a huge difference between the 15 cm Ytongg and the 17.5 cm KS wall in terms of the allowable load. Ytongg probably does not go beyond 10 N/mm2, KS only starts well above that. No one here has disputed that it is technically feasible. But okay is not the same as good.

Perhaps the structural engineer also planned reinforced concrete columns in the walls. That would work well due to the full insulation.

My normal interior walls also have to be chased.

According to the recognized rules of technology, horizontal chases are only permitted in walls with a thickness of 175mm or more without proof. Applies only to load-bearing walls. If chases are made anyway, each chase must be statically verified. I just call that a house of cards.

Oh, I meant the partition wall