Single-family house new construction, between rafters. or cold roof

Good day dear community,

I am currently planning our house (construction start around early April). At the moment, I am considering how to make the roof in the most sensible and economical way.
It will be a single-family house, 1.5 stories, 148 sqm, KFW55, 1.75m knee wall with a 30° pitched gable roof. ([Cross section attached]). The house measures 9x11.5m.

Would you prefer insulation between the rafters or a cold roof where "only" the top floor ceiling is insulated? I have already read a lot online, but I haven’t really come to a conclusion.
Due to the height of the knee wall, the roof will have no windows and, due to the air-water heat pump, no chimney either (a fireplace is also not planned; my girlfriend and I don’t like those things). The roof should be decent. Nothing spectacular. It should simply work. Since we want to build without a basement, we only want to use the small attic for boxes and a bit of clutter.

My questions:
Which type of insulation is easier to implement? How could such a structure look concretely?
I have already looked at a few examples on ubakus and don’t know what would be more sensible.
I think that insulation between the rafters would be more sensible because we wouldn’t lose height with this type. The attic is only very small. However, it is not really sensible to insulate a room that is only used for boxes or the like...

I would appreciate any tips.

Best regards

How do you want to realize a cold roof with knee wall on the roof? For me, it's a continuous concrete ceiling, roof construction, and roof tiles.

Just asking out of curiosity?

We have insulated the roof rafters. 1. Attic expansion reserve - does not apply to you 2. Relatively constant temperatures in summer and winter. For storing boxes and stuff, it is not beneficial if it freezes or reaches 30 degrees and more in summer. 3. In our second apartment - attic apartment with cold roof above, there is a draft through the hatch of the attic stairs

So how do you want to realize a cold roof with a knee wall on the roof? For me, it's a continuous concrete ceiling, roof structure, and roof tiles.

Just asking out of interest?

Cold roof was maybe the wrong expression.

I am considering whether I should "only" insulate the top floor ceiling or also the attic in the form of insulation between the rafters. I have to insulate the slope in the upper floor, that is clear to me. It's only about the floor.

My tip:
Insulate the attic. Ideally combine insulation between the rafters with insulation above the rafters (e.g. 8cm wood fiber). This way you avoid critical transitions and don’t take away the very limited space in the attic.
How do you get enough light into the upper floor?

We insulated the roof rafters. 1. Attic expansion reserve - does not apply to you 2. Relatively constant temperatures in summer and winter. For storing boxes and stuff, it is not beneficial if it freezes or gets 30 degrees or more in summer. 3. In our second apartment - attic apartment with a cold roof above, there is a draft through the hatch of the attic stairs

thanks for the tip

My tip: Insulate the attic. Best to combine insulation between the rafters with insulation above the rafters (e.g. 8 cm wood fiber). This way you avoid critical transitions and do not take away the very limited space in the attic. How do you get enough light into the upper floor?

thanks for the tip.

On the upper floor we basically have 4 rooms. Bathroom, bedroom, child 1, child 2, (storage room and dressing room not counted for now). On the gable sides there is one window element measuring 1.5x2.25 m each for every room. In addition, the bathroom and the two children's rooms get a "clerestory window" in the knee wall. Dimensions approx. 1.5x0.7 m. In the hallway / gallery, two windows 1x2 m will be placed one above the other. That should provide enough light on the upper floor. On the floor I don't need daylight. A lamp will do there.