Expandable attic in the new building, what can be done later?

Is dry screed actually suitable for underfloor heating?

Of course it is. It's not even exotic, but something you can get anywhere (if you want).

That is why I am currently not investing any response time in this (in my opinion follow-up questions) thread.

As a future owner, I see it differently. That is why this thread exists—to explicitly address this question, which concerns us greatly because we need to answer it promptly.

I, as a future owner, see it differently. That is why this thread exists, to explicitly clarify this question, which concerns us greatly because we need to answer it promptly.

I only copied this remark here so that readers of this thread only (i.e., those who do not also read your main thread) are not surprised as to why I apparently do not help here. I do help, but first in the main thread—and it is becoming clear there that the questions that build only on this dissolve into thin air.