Basement insulation interior wall new construction

I am just very unsure right now which option I should choose. I think (and hope) the basement is hopefully already sufficiently insulated with the 120mm insulation under the basement slab + 100mm perimeter insulation on the exterior walls. Additional interior insulation might be better for the room climate, but ultimately I think the underfloor heating will provide enough warmth here.

What is it because of? Too little information? Or what are you struggling with so much now?

What is the reason? Too little information? Or what are you struggling with so much now?

It is probably simply due to my dangerous half-knowledge :P I'm just not exactly happy with the polystyrene interior insulation, which is also not insignificant in price. From your point of view, would option 2 be the best here (without insulation)?

Now I have read something about climate boards (calcium silicate boards), which are said to be very good for interior insulation in the basement. As you can see, I am torn back and forth about whether I even need interior insulation in the basement at all (after all, the basement corridor is open to the ground floor) and whether I should just stick with the electrical installation from the factory in the prefabricated elements. However, hobby room 1 is supposed to also house a home theater, and acoustics do play a role there.

It's probably just due to my dangerous half-knowledge. I'm simply not particularly happy with the polystyrene internal insulation, which is also not insignificant in price. From your point of view, option 2 would be the best here (without insulation)?

Now I've read something about climate boards (calcium silicate boards), which are supposedly very good for internal insulation in the basement. As you can see, I'm torn about whether I even need internal insulation in the basement at all (after all, the basement hallway is open to the ground floor) and whether I shouldn't just stick to the electrical installation from the factory in the prefabricated elements. However, Hobby Room 1 is also supposed to house a home theater, and acoustics do play a role there.

How about a middle-ground solution? You do the cheapest option first, and then you can always "upgrade" to the second option later.

The interior insulation is, if I understood correctly, only a voluntary additional option. If you don't choose this, the exterior insulation alone must at least meet the Energy Saving Ordinance. Mainly, the electrical installations are done on the interior walls and if anything is done on the outside, then surface-mounted. The basement is not meant to be a 100% showcase. The basic acoustics don’t care whether you have a concrete wall, gypsum board, or calcium silicate boards. All are almost equally sound-hard and reflective.

What makes me more suspicious, however, is the unheated room. It is also within your thermal envelope and the other rooms basically heat it. The times of saving by not heating a room are over. I would also install underfloor heating there and at least provide basic temperature control.

However, the hobby room 1 is also supposed to house a home cinema, and acoustics do play a role there.

Hence the phrase "going to the basement to laugh" SCNR

Now I have read something about climate boards (calcium silicate boards) which are apparently very good for interior insulation in basements. As you can see, I am torn back and forth about whether I even need interior insulation in the basement

Just leave the climate boards aside, they are only suitable for the renovation of old buildings without or with only little exterior insulation.

120 mm WLS035 against soil results in a U-value of approximately 0.27 W/m²K. Considering the lower heat dissipation in the soil (factor about 0.5), this is energetically better than a normal exterior wall according to the Energy Saving Ordinance (<0.24). Applying additional interior insulation now neither helps energetically nor climatically, since the surface temperature is only marginally increased.

If you are "afraid" of too much heat loss: is strengthening the exterior insulation to 140-160 mm not possible? That should be significantly cheaper.

Gypsum boards are of course more pleasant than bare concrete.