Thank you for your information. Then we will possibly do double insulation for the pipes, that should work.
The exterior walls with 270mm are not normal, no. Normally it would be 180mm or possibly even less. As far as I understand, the fewest take 240mm and 270mm. However, the thermal insulation is particularly good because of this, especially in summer, which is worth it to me.
One more question about the stairs: If there is no landing, but that should be the lower part, do you then have to keep 1 meter depth clear where the wall is now? It's still not quite clear to me how you get up there... and the basement stairs then go down from the pantry? Or exactly the other way around, but then you stand in front of the wall on the upper floor when you go up?
We will draw another round. If anyone has any suggestions: feel free to share them.