BB/@københaven:
Before you make an attack, I would strongly advise you (also due to your other thread) to consult an expert/energy consultant.
3 reasons:
1) the investment volume is not insignificant
2) the measures taken should be compatible/coordinated with each other
3) even if you don’t manage to fully convert to a Kfw55 house, you might still benefit from low-interest KFW loans or repayment grants or investment subsidies through a clever selection of individual measures.
By the way, the costs for the energy consultant are also subsidized by the KfW.