Timber frame house on concrete basement / base insulation

Hello, I have been shown various options in recent days to deal with the problem of the "protruding" wooden house over the floor slab (basement ceiling) or basement wall insulation. Our builder would build a 30cm concrete wall on the concrete part embedded in the slope (the rest will be 36cm bricks without insulation) and insulate it with only 6cm PUR. He says it is not optimal but since the part is embedded in the slope, it is easily sufficient for Kfw 70?

Have others already found different solutions to the insulation problem here, or am I missing something?

Thanks and regards

Hello,

.....He means it is not optimal but since the part is within the scope for Kfw 70, it is easily sufficient?...

The assumption with all due respect, but usually the admissibility of the mostly used flat-rate surcharge (0.05 W/m*K) requires a consistent execution of the thermal bridges according to DIN 4108 Bbl. 2. Individual deviations from this are not permissible. Otherwise, detailed proof of all thermal bridges!
This can potentially become very expensive.
I hardly believe that this construction can be found in 4108.
Since there has been a lot of malpractice with this in the past, equivalence proofs must now be provided!
The client is always responsible in the external relationship, not the agent!

Best regards