Large dormers or high knee wall?

I actually don’t understand why the areas labeled as "Estrich" are walled off separately.

What is "Estrich" to the Swiss is, according to German usage, an attic / loft; in this specific case it probably corresponds to the space behind a knee wall.

I have quoted the passage from the 2018 fact sheet on floors.

"The cantonal (or municipal) law can therefore limit the dimensions of roofs with design regulations if necessary, for example by restricting the roof pitch or indirectly by limiting usable space in the attic."

Aha, ok… however, a usable area only results by enclosing it with walls. Without that, it is just "floor space".

If another opinion is still relevant:

I know both and would choose the higher knee wall if the floor plan is suitable.
The prerequisite is, of course, that the windows still work in all rooms. We now have a knee wall at 1.80. I think it's great, especially for arranging furniture in the room. Our small house also feels really spacious upstairs because of it.
However, the roof pitch for skylights is very steep and still relatively low for strip windows. You can probably work around that, but a window at knee height takes some getting used to.
We have large windows on the gable side for that reason, so it is still very bright and the roof can be fully used for photovoltaics.

I actually don't understand why the areas labeled "Estrich" are independently bricked in. They are not counted as part of the floor if they are under the roof, meaning they do not have their own standing height. So even if the walls aren't there, we are in the non-full-floor area. Including this space, the rooms become nicer. And what are the expensive roof windows for? They are located exactly where there are already windows in the gables.

maybe the fundamentals are different in CH. ;)

Exactly, from a clear height > 1m it counts as area. We no longer have living space, but still have ancillary space.

If another opinion is still relevant: I know both and would choose the higher knee wall with a suitable floor plan. Of course, the prerequisite is that the windows still work in all rooms. We now have a knee wall of 1.80. I think it's great, especially for furniture arrangement in the room. Our small house also feels really big in the upper floor because of it. However, the roof pitch is very steep for roof windows and still relatively low for light bands. You can probably fiddle it in, but a window at knee height takes some getting used to. We have large windows on the gable side, making it very bright nevertheless, and the roof can be used completely for photovoltaics.

That makes me think again. Most people here speak out for the higher knee wall. We probably can't go up to 180 because the roof pitch would become too shallow, but maybe we'll ask again. Because the clear height under the ridge can be a maximum of 340 cm, otherwise a virtual intermediate floor is inserted, whose area would be counted again...

Unfortunately, we have had to realize that the knee wall increase also means that we would have to reduce the bay window by one grid size (62.5 cm), since the entire upper floor now has a clear height of > 1 m. Another argument against it. We could reduce the basement slightly (ancillary area budget) and correspondingly enlarge the kitchen-living area (ancillary area -> living area) to maintain the bay window.

We also have the beautiful distant view with a section of the Alps on the eaves side.