Ground floor approx. 100 sqm, upper floor expandable (planned bathroom, 2 children's rooms, 1 storage room)

Now with this observation, you can take your place at the back in this thread. I'm afraid the OP will run away from us if we just keep complaining. Solutions are needed.

Out of money? I would also consider completing the roof insulation now. That way, you can also show the "botched planner" his nonsense right to his face. Maybe he'll lower the price.

You made the wrong statements about the position of the windows, and I wouldn’t call the simplistic calculation ignorance.

Now I’ll slowly show you what can be seen in your picture. Namely, that an “k” is missing – you have no knee wall!



I highlighted in blue the exterior wall, here mentally extended up to the top edge of the ceiling beams. In red is the position of the absent foot purlin here. Its bottom edge lies “0” above the blue area, so knee wall 0.

The difference between the length of the green line and 0 is simply due to the “scissor” caused by the roof pitch. That is not a knee wall, that is simply a plumb line set on a slope.

If you estimate a floor buildup from the foot of the green line, it will still roughly be about 12 cm long – which by no means makes it serious to proclaim a 1m line another 88 cm away.

The construction of the roof overhang itself is economically designed; given current cornice box fashion, this is a clever solution for a laundry line attic (that is the polite wording for “the bastard who planned this as a living space reserve should publicly hand in his diploma”).

If the conversion is not to become unauthorized construction, the planner is going to sweat a lot to make this thermally acceptable for approval. Starting with the non-existent exterior wall in the attic, it won’t be a walk in the park to get this upper addition tight to the thermal envelope.

Your idea to count a furring strip added on the rafters, which is necessary solely due to the thickness of the insulation membrane, as the counter lathing is nonsense from the same stable as the ten-centimeter floor.

I find this concept of the couple apartment with “build now, think later” attic irresponsible; a professional should have stopped you by all means.

Since there is a full bathroom downstairs, a small shower bathroom upstairs would be enough.

Due to the planning of an apartment for 2 people on the ground floor and a normal upper floor of a family home upstairs, you get
2 master bedrooms
2 full bathrooms and
mini rooms

The house is too small for that.

Why isn’t the roof insulated and integrated into the thermal envelope right away upstairs?

Now with this observation you can queue at the back in this thread.
I’m afraid the OP will run away if we only keep complaining. Solutions are needed.

Money all gone?
I would also consider going ahead with roof insulation now. This way you can immediately show the “botched planner” his nonsense. Maybe he’ll reduce the price.

I just assume that it is not – by plan and photos alone some things here are not clearly defined. Without a detailed cornice box termination I would actually expect the ground floor as a closed envelope here, but then with an inset stair or boxed-in staircase.

I fear that even with a serious ERNSTL one cannot solve this yet.

Is it that simply possible to integrate the roof into the thermal envelope? If I understood the OP correctly, the building permit runs with energy saving ordinance calculation with insulation of the ceiling. Even if he insulates upstairs, the ceiling including the insulation according to the building permit must still be provided, or am I missing something?

Would such a solution work?

Yes, the ground floor is its own shell. My approach was also that only the stairwell (with MZ door as entrance) is enclosed and insulated.

Is the position of the ascending Rosa in your non-scale sketch supposed to represent the knee wall to be constructed? - then it should work like that.

Is this identical to the approval planning, i.e. insulated ground floor with enclosure/wrapping of the stairs, and otherwise empty attic?