Single-family house 175 sqm without basement, too big?

Ceiling height in your living space at least 2.70m. But I’m also a fan of open space and not a standard. Also think about acoustic measures to make the living space comfortable.
Enlarging the staircase would fit with the overall spaciousness.

For Junior in the north, it is certainly great for everyone in the long term to have their own entrance from outside, a mini kitchenette, and a private bathroom – like a separate apartment. The third room upstairs would be significantly smaller because of this, but the upstairs hallway could also be optimized since the corridor to the bathroom would be eliminated – then again the arrangement of the bedroom-dressing room-bathroom combination would have to change... Actually almost everything new...

I would add another window in the utility room
Possibly also one in the pantry

Our son has now been living for about 6 years (since he was 14) in a room with the shutters closed. I believe there hasn't been a single day since then when the shutters were up. With such behavior, I wouldn't give the junior a sunny side either.

Best regards
Sabine

For Junior in the north, it is definitely great for everyone to have their own entrance from outside, a mini kitchenette, and a private bathroom – like a granny flat. The third room upstairs would become significantly smaller because of that, but the upstairs hallway could also be optimized since the corridor to the bathroom would be eliminated – then again, changing the arrangement of the sleep-dressing-bath combination... Actually almost everything would be new...

Now I can imagine what is meant by apartment. That sounds great, but honestly: how many young adults still living in their parents' house want to cook? I know some who had such a kitchenette as teenagers / young adults, and none of them used it adequately. I definitely would not install a kitchen just for a frozen pizza and a cold cola. I see the bathroom similarly. He gets a spacious room, and in my opinion, that is enough.
I will definitely reconsider the rest, especially moving the rooms, once I know how big the staircase will really be.

Yes, I had also thought about the windows, although I wonder if they are really necessary? Especially in the utility room, I imagine it would be more of a hindrance because I wouldn’t be able to put a shelf there...

Pantry with almost 4m² is quite large. I would rather give the WC a second shower. But that's a matter of taste. Just an idea..

It depends on what you do in the [Hauswirtschaftsraum]. For drying laundry or ironing, you will need a window. The heating system produces waste heat and the air becomes stagnant in the [Hauswirtschaftsraum] if you don't occasionally open a window.