ᐅ Timber frame house on a concrete basement / insulation of the base wall

Hello, recently I was presented with different options to address the issue of the wooden house extending beyond the concrete slab (basement ceiling) or the basement wall insulation. Our builder plans to build a 30cm (12 inch) concrete wall on the concrete part embedded in the slope (the rest will be a 36cm (14 inch) brick wall without insulation) and insulate it with only 6cm (2.4 inch) of rigid polyurethane foam. He says it’s not optimal, but since that part is embedded in the ground, it should easily meet KfW 70 standards.

Have others here dealt with insulation challenges like this, or am I missing something?

Thanks and regards

Hello,

Dipl-WiING schrieb:
.....He means it’s not optimal, but since that part is within the range for KfW 70, it’s easily sufficient?…

The assumption is understandable, but generally the allowance most commonly used as a flat rate (0.05 W/m*K) requires a consistent execution of thermal bridges according to DIN 4108 Part 2. Individual deviations from this are not permitted. Otherwise, a detailed verification of all thermal bridges is necessary!
This can potentially become very expensive.
I hardly believe that this construction can be found in DIN 4108.
Since there has been a lot of misuse in the past, equivalence proofs must now be documented!
The client (homeowner) is always responsible externally, not the contractor or agent!

Best regards.