Insulation (exterior wall + under floor slab) WU basement sensible

Hello everyone,
I decided against this insulation back then due to costs:
- 14cm perimeter basement exterior wall (approx. 18m long x 2.5 high): 6,600€
- Thermal insulation 10cm under the floor slab (approx. 10m x 10m basement): 7,300€
Now I regret it a bit and am considering whether to commission this position now.

The basement is partially exposed.
All basement exterior walls (exposed) I planned with 16cm ETICS. It is now only about the exterior walls that are under the ground. The basement is not a living basement (no toilet, no heating)
Construction is done with a general contractor. The advice from the architect was underground (You get what you pay).
Question:
- Is it sensible to do the perimeter insulation exterior wall for the price?
- Same question for insulation under the floor slab. Here I think it is somewhat difficult since the building permit already exists. Alternatively, I am thinking of glass gravel. I do not know the price of the glass gravel.
- An acquaintance mentioned "insulation under the basement ceiling" to me. He says otherwise it leads to cold fracture. What do you think about that?
THANK YOU for your opinions.

So an exterior wall is a must in my opinion, otherwise you will almost certainly get mold and other problems.

Under the floor slab is unnecessary luxury, we did it. It brought no benefit at all. You don't save on heating costs because of it. And otherwise it has no added value either, definitely save on it.

So exterior wall insulation is a must, I think, otherwise you will quite certainly get mold and other problems.

Insulation under the floor slab is unnecessary luxury, we did it. It brought nothing. You don’t save any heating costs because of it. And otherwise it has no added value either, definitely save on that.

Hello Bookstar,
thanks for your answer. I will additionally book the exterior insulation for about €2300. There is a choice of 10 or 14 cm.
I will forgo the insulation under the floor slab.
What kind of basement do you have? (WU, residential–utility basement, ...)? When was the house built?

Built 3 years ago, a mix of residential and utility basement made of WU concrete. No bitumen coating.