KfW from 57 to 55 - Calculation and Certification, Expert

Hello everyone,
I received the calculations from our expert for the KfW today. The Qp reference value is 77.5 kWh/(m²a). The value for our house (monolithic wall construction, no ventilation system, air-water heat pump, no solar, no photovoltaic) is 44 kWh/(m²a). That results in 57% and thus practically a KfW57 house.
We had previously planned with KfW70. Now my questions:
Are there measures (e.g., decentralized ventilation with heat recovery in the two bathrooms) that are cheaper than the €2,500 repayment subsidy and would presumably allow us to get below 55%?
My primary concern is not the KfW55 certification itself, but rather possibly achieving higher comfort at no additional cost.
What additional costs are incurred for the KfW55 certification compared to the 70s? Of course, the calculation would have to be redone. Anything else?
I will of course discuss this with my contractor again later this week, but I want to get information beforehand.
Thanks in advance!

Have you already applied for the loan at the KfW through your house bank? Then the matter is, in my opinion, already settled.

Can only agree with toxi on that. If KfW 70 has been applied for and possibly already completed, the thing is done.

Have you already applied for the KFW loan through your house bank? Then the issue is, in my opinion, already settled.

No, not yet. That's why I'm asking.

I can’t help any further. I only know the part that concerns the bank. An architect or, better, TWP must help you with that. Who accompanies and confirms the part for you? That person must be able to tell you with what effort it is best to solve it.

H`t still counts. You have to go from 85% to 70% of the reference building. You can still optimize this mathematically with a detailed heat bridge verification.

Do you already have the calculations electronically and can you upload them here?