New single-family house drawings

The minimum requirement is (probably also depending on the federal state) 0.125 m² window rough opening size per m² of room area. However, I have also read that one should rather aim for 0.2. I agree with Yvonne - floor-to-ceiling windows on the upper floor you really have to be aware that you lose space for furniture, people can look up your skirt if they are sitting in front of the window, etc. it feels less cozy. We are considering, for example, choosing a 0.6 m parapet height (a kind of compromise).

We have also decided on a 50cm sill height on the south side in the upper floor and attic. This way, the children can sit, play, paint, set up toys, etc. on the windowsill. Below it is space for a low shelf or similar, and the children can still look outside while playing. The two almost floor-to-ceiling windows with a 25cm sill height, which we will have on the east and west sides in the attic, were chosen purely for space reasons. Wider ones were not possible due to the room layout, and the rooms with 19-20 sqm are large enough to allow alternative options for furniture placement. But that also remains a matter of taste. From a practical point of view, wider windows are more effective.

There have already been some good comments.

One more note: if the pantry is not accessible from the kitchen, I would simply assign the room to the utility room.

Why do the children get the smallest rooms? 13m² is okay, but relatively small overall. In my opinion, 12 m² each are enough for the bathroom and bedroom, but I would make the children's rooms much bigger. You are usually only in the bedroom at night. The children, however, spend much more time in their rooms. Galleries are always a matter of taste...