Perimeter insulation of unheated room, yes or no?

[ATTACH alt="gedämmt-Außenwand-Massnahmen-waermebruecken-dämmen-64077-1.jpg" type="full"]2788[/ATTACH] Our exterior facade was already equipped with ETICS last year, but only up to the bottom edge of the basement floor. The basement floor is insulated from above, i.e. screed removed and insulation applied on top.

Now it is about the area of the exterior wall below the basement floor. On the south side, there are still about 2 meters of exterior wall, up to 1.2 meters above ground level, the rest is in the soil; on the east and west sides, there is a wedge exposed that rises from 0 meters above ground surface up to 1.2 meters above terrain level towards the south.

Does this area also need to be insulated? Since this situation rarely occurs in normal house construction, I can’t find any information about it.

Behind this exterior wall there is no room, but earth/gravel, so the area behind the wall is of course unheated. However, the exterior wall here also represents a thermal bridge, as heat from the basement, which is heated, can get into the wall and flow downwards. The question is simply whether it makes sense to insulate the wall from the outside while it cannot be insulated from the inside because the inside surface adjoins soil. I think this is simply an unavoidable thermal bridge?

I would like to clad the plinth with natural stone, which does not adhere to insulation boards, so I tend to forgo the perimeter insulation.

Or would that be an energy-related sin because at least the accessible external area should be insulated? Attached is a picture for better illustration.

Addendum: The interior walls of the cellar are insulated with 3 cm of styrofoam. In addition, the cellar exterior wall on the left in the picture cannot be insulated under any circumstances, as there is a building above it that would have to be demolished to carry out the necessary earthworks, which of course is out of the question. Since this occupies a fairly large area, in my opinion it is negligible if the base is not insulated; the situation is unsatisfactory in any case.

....or would that be an energy-related sin because at least the accessible outdoor area should be insulated?

What is your planner's opinion on this?

Best regards.

My energy consultant, who specified the measures for the Effizienzhaus 100, said that insulation could be added there, but it is an old house with unavoidable thermal bridges, of which there are still plenty. If money is left over after the mandatory measures, it could be addressed, but he did not include this measure in his calculations for transmission heat loss. Other areas must simply be better insulated for that. Since there is still some money available now, we are considering whether to use it for the perimeter insulation or prefer another measure. As mentioned, we still have other thermal bridges, such as a cantilevered concrete slab as a platform for the front door, the rear basement area in the ground, which cannot be insulated from the outside (but can from the inside), exposed load-bearing columns that are also directly connected to the ceiling of the ground floor, and the floor in the split-level, which is not suitable for conventional floor insulation due to the ceiling height, but certainly for vacuum pads. The energy consultant only comments vaguely, such as "it can all be done" or "it's all a question of effort," but that doesn't really help us.