Gas heating without solar thermal?

In my opinion, KFW financing only makes sense if you are already building a house that meets the requirements of the KfW.

It is hardly ever worthwhile to adjust a house planned without regard to the KfW requirements to meet the KfW standards.

However, there is no hassle if you take out a KfW loan additionally through your house bank.

It is almost never worthwhile to retrofit a house that was planned without considering KfW requirements in order to meet KfW requirements.

I'm not sure if I understand this correctly. You have to comply with the Energy Saving Ordinance anyway. I assume that the house already somewhat falls below the maximum allowed values. We just have to ensure that this is the case by 15% in order to be able to forego solar thermal energy. We don't actually want to tailor it to KfW requirements.

If you don't want [KfW], you don't need to have the house planned for it.

I believe I now know where our "misunderstanding" lies.

My question or assumption was initially that the proof of undercutting the Energy Saving Ordinance is equivalent to a KfW certification, since that goes beyond the Energy Saving Ordinance proof.

However, it seems to be correct that it is sufficient to demonstrate the targeted undercutting of the Energy Saving Ordinance through the two key figures in the Energy Saving Ordinance proof – and that no further costs arise in this regard, since an Energy Saving Ordinance proof must be provided anyway.

Exactly, as long as you follow the requirements of the energy saving ordinance, you can insulate better, install more technology, or do whatever you want.

This has nothing to do with KfW funding until you want to make use of it. Then, in addition to the energy saving ordinance, you must meet the requirements of the KfW for the respective programs.

You will only be allowed to build a house in Germany if you comply with the Energy Saving Ordinance and the Renewable Energy Heat Act (in addition to other requirements, e.g. the structural engineering must meet the requirements). You are not allowed to just build whatever you want.

The KfW grants particularly favorable loans for houses that are now even "better" (=more energy efficient) than those houses that merely meet the legal (minimum) requirements. (The KfW also grants other loans for which this does not apply ... The conditions for these loans are determined by the KfW in each case.)