Floor plan of a single-family house on a gentle north slope

You can currently forget about the KfW loan when it comes to the interest rate. If the house is already an energy-efficient house, you can possibly push the effective interest rate into competitive ranges with the repayment subsidy – but this doesn't work if you have already offset necessary additional costs with it. Therefore, it's better to plan without KfW for now. (If it should be useful in your specific case, you can still include it)

We are building a passive house that falls under Kfw 40.
Structure of the floor slab:
20 cm gravel
28 cm insulation
24 cm floor slab (for structural reasons)

I assume the basement is included. We had an option with the unfinished attic.
I would put the washing machine in the upper floor with the bedrooms, where the laundry is generated.
Swap Child 1 and the bedroom.

There are stones that allow for monolithic wall construction at KFW 40. At least occasionally there are articles in magazines. You have to google it.

Solid wood + WVS is also possible.

If the subsidy causes no or not much additional cost, I would also go for KFW 40.

Find a construction company that builds to KFW 40 standard as a matter of course.

Do you really want to orient living, dining, kitchen, and terrace towards the street? Personally, I wouldn’t like that at all, and it doesn’t matter whether it’s a main road or the end of a residential dead-end street.

Can you elaborate again on the orientation? The question of whether you want your living room + terrace facing the street?

Can you elaborate again on the orientation? The question whether you want your living room + terrace facing the street?

It's basically a justified point. The terrace is planned on the south and west sides, so around the corner. Of course, this has the disadvantage that the living area is relatively visible.

Currently, there are about 8m from the house to the street in the south. With a 3m terrace, there remain 5m to the street. Unfortunately, the plot is not bigger, and on the north side there must also be a 3m distance to the boundary.

But it will improve sooner or later when shrubs on the street side reach a height of about 1.5m. Since garages of the neighbors are relatively close again on both sides left and right, the light incidence especially from the west is not very good. We have also considered the variant where the kitchen was in the northwest corner, but in the end we did not like it that much. And no one will probably want to orient it to the north.
In the current solution, you also have from the kitchen a view of who is coming, etc. I quite like that.

Of course, a south slope with the street to the north would be better. In the case of a slight north slope with the street to the north, however, you have the clear disadvantage that you then either have a retaining wall or an embankment right in front of you on the south side, and you have a lot of earthworks to dispose of. The basement would also be completely underground in this case. That’s why we consciously decided on the street on the south side, with the mentioned disadvantages. But we are happy to accept them.

I would put the washing machine in the upper floor near the bedrooms, where the laundry accumulates.
Swap Child 1 and bedroom

The room with the optional children's bathroom would be suitable for that. The connections would already be in that room. It’s a good idea to do it like that. Whether it then stands there or in the basement in the heating room can be freely decided.

Swap Child 1 and bedroom

That would be possible anytime since neither the children's room nor the bedroom requires any other installation. Apart from network/TV/electrical installation with light switch at the bed. We would provide that anyway for all rooms.

When considering the property, think about whether the house should generally, without looking at the floor plan for now, be rotated so that the house opens to the west garden. But even if it should remain as is, I would orient the interior more towards the southwest, for example swapping the guest room with the kitchen.

You don't have to loosen up with a bay window, you can consider breaking up the windows or/and planting directly at the house or terrace.