KfW 55 with wooden house - U-values: Wall 0.18 - Roof 0.16

Hello,

in search of a construction partner, my wife and I found a regional carpentry company that makes a very good impression on us and with which we can very well imagine a collaboration.

What we like is the ecological construction method. In addition, the provider offers the installation level that I require as a must, which other prefabricated house manufacturers usually do not offer at all or only in the "expensive" passive house walls.

The price also seems to be okay – especially because the aforementioned ecological construction method lowers our land price through a funding program.

My goal is to have a KFW 55 house – not (only) because of the subsidy, but also because of permanently low operating costs – again noted here: achieving the KfW55 standard would make the land considerably cheaper again.

The U-values on request:
- Exterior wall: 0.187
- Roof: 0.166

In addition to geothermal energy, a controlled residential ventilation system is planned.

Are the U-values still "common" today? I think the roof is quite good, but the exterior wall only average compared to other providers.

Thanks and regards
Markus

Yes, that's fine - with some effort, Kfw55 can be achieved (without knowing about doors, base insulation, etc. now). Have them give you the exact wall construction - that is, all layers with thicknesses.

Outside - Inside
60mm softwood fiberboard with plaster
120mm cellulose insulation
15mm OSB airtight glued
100mm installation level (with cellulose)
15mm drywall

Roof (outside - inside)
Roof tile
Counter battens / battens
16mm DWD board
280mm KVH with cellulose
diffusion-open membrane
30mm battens
12.5mm drywall

Regards
Markus

Best to put this in the forum on u-wert and post it, then wait for the reactions. Besides the constructions, other things also play a role: who is planning for you then? Is the carpenter the general contractor or just doing the "shell construction" etc., who is the site manager?

They are working with a freelance architect and otherwise have almost all trades in the house or through local partnerships. It would be basically turnkey.

Supervision / inspection would then be carried out by our experts.

Regards
Markus

If the architect knows what he’s doing and has approved the wall structure, why not.. he probably knows more anyway (especially since he also knows the entire project).