Upgrade new condominium from KFW55 to KFW40: Is that possible?

Hello forum,

I want to buy a condominium from a developer (100m²; ground floor). The apartment will be located in a building with approximately 20 residential units and all apartments will comply with the KFW 55 standard. The apartment has only 4 windows (all floor-to-ceiling; 2 double windows/terrace doors; 2 "normal" windows) as well as a small bathroom window. Heating is via underfloor heating through district heating and hot water via solar.

If the apartment were KFW 40, I would be entitled to the KFW 300 subsidy "Homeownership for families." With the loan, I would save about 80,000 euros in interest over the next 20 years, maybe more.

So my question is: Where would one start to turn a KFW 55 apartment into a KFW 40 apartment? A) If the apartment is already completed B) If the apartment is already at shell stage (windows are already in, but inside the walls and floors are still all "virgin" and the facade is not yet insulated)

More external insulation? Better insulated windows? ...? And can this be done for significantly less than 80,000 euros?

I understand that you cannot give me a 100% certain answer and of course an energy consultant would be needed. But for now I am looking for a rough estimate if it is even worth continuing to think about it.

Best regards Torsten

Therefore my question: Where would one start to turn a KFW55 apartment into a KFW40 apartment? More exterior insulation? Better insulated windows? ...? And can this be done for significantly less than 80,000 euros?

Where to start? The developer has to convert the entire building to 40. Individual apartments are not possible, since the entire building is considered.

Where do you have to start? The developer has to convert the entire building to 40. Individual apartments are not possible since the entire building is considered.

Ok, thanks. I didn't know that KFW is always considered for an entire house.