Insulating the knee wall exterior: with what and how to attach?

Great, now I at least know the terms. Thank you very much! It is, as you write: the knee walls are to be insulated from the closet side. It's also good that it makes sense this way already. Who now has the idea with what and how to fasten? Best regards Andreas

Insulation will only increase the temperature of the knee wall. But what will probably bother you more is the draft, and you won't get that under control with a little mineral wool. Tape the joints of the Heraklith boards and the hatch with tape; you won't be able to do much more there without greater effort.

Yes, the effect is zero, in the cavity you will also get mold problems. Buy a fan heater, it is cheaper and more effective for the 2 years.

It is, as you write: the knee walls are to be insulated from the non-room side.

Nice that I at least understood you correctly.

Good also that it makes sense this way already.

There are opposing opinions on that; and I only meant: if at all, then at this point: insulating on the non-room side of the knee wall or on the room side of the knee wall I would consider less favorable placements.

Great, now I at least know the terms. Thank you very much!

As I said, normally you could file that under "pedantry on my part" – usually you only have one of the two, and then you can also call the knee wall a "Drempel" (or as you did here the other way around).

In this special case both knee wall and Drempel "apply," the differentiation in terms is more important, otherwise one quickly talks about the supposedly same thing but means the other – with the consequence of choosing the wrong installation side...