Planned house construction - garage/workshop below, living area above

The KfW presupposes the Energy Saving Ordinance. In this case, DIN 18599. Through zoning, you separated the non-residential area from the residential area.

And that is hopefully good. I do not believe it is profitable to pay the 200€ for this standard.

Approval feasibility: according to the building plan, there is nothing against a floor being 4m high.

And is the property located in a mixed-use area?

And the property is located in a mixed-use area?

Yes

Zoning creates great advantages, I was recently able to calculate an office and storage new building made from older office containers retrospectively. There were even shower rooms with 24° included. The Renewable Energy Act is often fulfilled by the residential zone, so depending on the heating system, you are exactly free from this critical point.