Site planning and floor plan - Your assessment wanted

If the ridge height remains the same and the knee wall becomes higher, then the attic even gains a little more volume.

I agree with Yvonne. For 1.5-story houses, I would also look for a knee wall between 125 and 130.

If you have a lot of stuff and need a storage room, there has to be a permanent staircase to the attic. Otherwise, I wouldn’t count on the space up there. Apart from the Christmas decorations, there is only stuff in our attic that could actually be disposed of, simply because it’s too inconvenient to quickly open the hatch and climb up the ladder.

With the knee wall, we thought that just under 90cm would be quite good,

Effectively less than one meter inside, I wouldn't want to have. My standpoint is: a knee wall has to completely replace a dwarf wall fully, otherwise it is of too little use. Using a classic dwarf wall would also be possible, but it would be associated with insulating the sloped side. Knee wall and dwarf wall as a combination is neither fish nor fowl.

We were told exactly the opposite... that raw construction measure means that there is actually more in the end,

Of course, after 1.5 cm of internal plaster, it would be 89 cm, that's probably what is meant. If it still counts at the top edge of the FFB, then it’s okay, but if it is given from the top edge of the RFB, then effectively there are only 70.

I once measured the headboard of my bed. It has a height of 97cm. This is a completely normal average bed from the furniture store.

I would also choose a slightly higher KS.

A box spring bed (which almost everyone buys over the years) already has nearly 50 cm in height. And now imagine the headboard: does it still look good if it has less height than the 50?

And then try to sit up under the knee wall that is not even 90 cm high. You might as well lie down again immediately because of headaches.