Can be done. It should not get too cold there / ventilation should be possible. Also, an interior wall of the bathroom or bedroom can be lightly insulated if necessary to meet the requirements.
Yes, I would plan a light well and/or [WRL] in every basement room anyway. For the bathroom, probably insulate to keep the heat in, and for the bedroom, however, rather the opposite, to keep the heat out?
So much for the theory, but whether it is really necessary can be determined by the heating load calculation. In any case, it would be relatively unusual, which doesn’t have to mean anything.
There is probably the possibility of an exemption. I can't tell you how that formally works. Or you have them installed and set to electrically off and open.
I also tried to get exempted from it. But had no chance, even though I also had a letter from someone at TÜV, who had outlined the issue of ERR, self-regulation effect, etc. But it was unsuccessful and considered too general by the building authority. They then almost wanted some kind of expert opinion that was specifically based on the building project. Then I withdrew my exemption application because it would have otherwise cost money. However, in HTD there are already several who simply got an exemption. It apparently very much depends on the federal state. For me in BW it was not possible. In the end, I did not install ERR, but prepared for it. If an inspection, which can happen, occurs, I would have to retrofit it. I am also satisfied without ERR. But there are exceptions where one can officially waive ERR at least in the control room. Unfortunately, you are not allowed to post links. Try googling the following: "Auslegung XIX-11 zu § 14 Abs. 1 und 2 Energieeinsparverordnung 2013 (selbsttätige Regelungseinrichtungen bei Zentralheizungen)" on the homepage of bbsr-energieeinsparung. There look at 4.)
Insulating this single room "pantry/wine cellar" on the inside with XPS or EPS against the "heat" of the surrounding rooms and completely omitting the floor heating would be nonsense? Why
A room does not become warm or cold through insulation alone. Insulation here only slows down the heating process but does not prevent it. Without active cooling, an equilibrium with the surroundings will inevitably be reached sooner rather than later.
it of course depends on the area of the exterior wall in the ground (because of the basement) and its temperature, right?
Theoretically, you could also omit this corner where the pantry is planned from the exterior wall insulation and just insulate the room as a cube within the envelope by insulating all the interior walls and the ceiling of the pantry, right!?