Neighbor wants to build a semi-detached house with an offset

So, the first question: Is he even allowed to do that, or is only a semi-detached house permitted on the property? Definition of semi-detached house in the land use ordinance. If strictly required according to the development plan, then the matter is settled.

needs its own firewall and may not extend insulation, plaster, or roof parts beyond the boundary.

I am rather thinking of compliance with the cultivation obligation, but with an underbite/overbite on the commune side.

The professionals also place a ventilation shaft on an "undivided own" outside.

I do understand it as “offset,” otherwise it would not be called an end wall. And also here: This will refer to the advanced side, which would not exist without the offset. The original poster threatens the same on the opposite piece. However, thermal insulation may be carried over the boundary, but I do not know whether the regulation only concerns subsequent renovations. Ultimately, regarding the question: Just ask how they imagine the side insulation: whether they would accept your insulation then? Then they might see the disadvantages, if the architect has not already told them.

he wants to plan the insulation on our property side.

The lender sees this critically,

The exhaust shaft is marked red then about 40 cm from his wall moisture will hit the cold wall,