Insulation under reinforced concrete floor slab KFW55

So 6cm insulation on the floor slab and then you want to achieve KFW55?

Do you have access to the calculation documents? Somehow I (layman) cannot imagine that this is supposed to fit together.

What exactly should I have changed? More insulation? The provider is always open to negotiation

How are we supposed to know that? What does the energy calculation say? What does the expert who provides the support for the confirmation for the KFW say?

You insulate only as much as the calculation by the energy consultant (or whoever calculates the thermal protection certificate) specifies in order to achieve KFW 55. If they say 6cm under the screed is sufficient, then that will be the case – although I also consider it unlikely.

We ourselves build KFW 55; in total, the energy consultant specifies 20cm insulation WLG 035. This component thus achieves U = 0.164 W/m²K. However, this is only an example; conceptually, it can certainly be done differently.

and how exactly is your insulation divided?

So far 6 at the bottom and 14 at the top. We will still turn it exactly or take everything down. Complete construction with ETICS and wrapping all around once seems logical. Also slab foundation, with strip foundations it would be different again.