Is KfW40+ possible even if photovoltaic and controlled residential ventilation were already required for KfW40?

Or you do it the way that makes sense, so possibly larger photovoltaics and storage.

I think you have to be careful not to chase after subsidies and also keep an eye on the actual costs.

If I remember correctly, for KfW40 the building envelope must be brought to a low transmission loss. "Compensating" with controlled residential ventilation is not possible – you really need the envelope (i.e., insulation values, etc.). The question is whether (and with which measures at what costs) you can get from a KfW55 envelope to a KfW40 envelope. Only once that is achieved can you add the plus package with photovoltaics/storage, controlled residential ventilation, etc.

Of course, the energy consultant knows all this even better :)