Massive construction in self-contracting & KfW 40

By the way, this is also where the consultants complain and say that the entire KFW funding process has become so complicated that it is no longer really worthwhile.

Unless you are building on a large scale (multi-family house) or building KfW 40 instead of KfW 55. The "surcharge" is then about €50/sqm of living space (when building with a general contractor), but without funding. One should carefully consider whether this might also be an alternative (or possibly offset the additional costs with interest rate advantages through funding during the first fixed interest period).

Thank you very much for the feedback, @familie_s! Did you find the energy consultant yourselves? May I ask what you installed regarding monolithic, 36.5 or 42.5 stones? Or something else?

Yes, we found him ourselves, but we took him on the recommendation of the shell builder. We used Schlagmann U8 unfilled at 42.5.

According to the Building Energy Act, instead of EH/KfW40, monolithic caliber 365 is sufficient at least in aerated concrete (but probably also in the pumice stones). Caliber 425 costs about 3% living space, in a standard replacement villa therefore about 14k extra. More important than regarding the energy consultant, I would especially follow the recommendation of the contractor concerning the wall structure (unless he recommends an unfilled porous brick, then I would switch to its filled variant). Unfilled porous bricks are resonance bodies. In addition, the filling also has thermal insulation value, so that can already tip the balance to manage with the normal caliber.