Again :) 40 (EE) was just an example. I was really only asking whether the subsidies can be multiplied by the factor 2 or 3.
What is realistic in the end remains to be seen.
Trying to achieve KfW 40 (EE) in existing buildings is a challenge even without considering the costs. First for the planner, then for the trades, and ultimately for the wallet.
In my opinion, it makes more sense to aim for KfW 70 EE with an additional individual renovation roadmap.
The additional costs for the isfp, if planning is done anyway, are negligible, and you receive an extra 5% subsidy on top of the 40% for 70 EE. Heating technology can be separately subsidized with 45% (otherwise 35%) when switching from oil, regardless of the KfW standard, plus 5% with the isfp.
The significantly higher subsidies for renovations in existing buildings compared to new construction are absolutely justified. Every new building, no matter how efficient, initially causes additional emissions and resource demand. Renovation, on the other hand, reduces actual emissions and resource use is generally also lower than in new construction.