Insulating the cellar from the inside - experiences?

Hello everyone,

I want to use a room in the basement as a multipurpose room, that means for me a photo studio, guest room, home theater, or sometimes a playroom for children. I might insulate the basement from the inside. I just want to have a nice feeling when I am in the basement, but before I ask my question some key data:

* Room size 25m²
* House surrounded by drainage in the ground at the floor slab
* Have about +22° on the ground floor (living room) naturally heated with underfloor heating
about +3° currently outside
about +13° in the basement room (unheated)
The house is actually very well insulated from the outside everywhere, therefore also a low temperature difference from basement to ground floor.
* Single-family house facade 20cm insulated (built 2009)
124m² living space annual heating costs with natural gas about 650,- Euro
* Fully basemented, basement is completely underground
Basement is insulated from the outside with 8cm
* SOIL-DIMPLED MEMBRANE-INSULATION-WuBETON 25cm-BASEMENT INTERIOR
* Basement is dry everywhere, no mold or similar
* Want to equip with underfloor heating.
* I am aware that I also have to insulate other colder rooms.
* Insulation costs are rather secondary

Now to my question, how should I insulate with thermal plaster, gypsum wall, or Styrodur/Styropor. Does it even make sense? Actually the basement is already insulated. I am not a layman but also not a professional on this topic, so I ask for opinions.
Thanks in advance.
(Sorry for my bad German, I am not an Alleman)
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Hello everyone,

does no one have an opinion?
ok, never mind.
In the meantime, I have decided on thermal plaster.
At first, I was a bit skeptical whether thermal plaster really has an effect.
Now I have bought thermal plaster (Baumit thermal plaster, it is even very inexpensive, 40l around 7 euros) to try it out, and applied a small area (1cm thick).
2 days later I touched the area with my hand, and look, the area is noticeably warmer. The concrete surface feels very cold.
Therefore, I will plaster the basement walls with thermal plaster.
(with 1cm plaster rail)

Advantages:
- easy to work with, works very well
- one bag 40l about 7 euros
- one bag is very light, weighs very little despite 40l
- walls can breathe
- you can still hang pictures on the walls without special dowels and the like.
- can be processed without a machine

Disadvantages:
- I don’t know any, do you perhaps?

Is the thermal plaster applied over the entire surface of the concrete? Otherwise, you’ll get thermal bridges (condensation) between the plaster and the concrete wall? In other words: The plaster will take on the temperature of the concrete? Have you installed additional heating? Or do you only want to raise the temperature using insulation? Our basement is 18 degrees without heating thanks to the external insulation. Inside, there are raw concrete walls. If everything works out for you and you manage to raise the temperature by 3-4 degrees, I might also put thermal plaster on mine.

Thermoputz lies fully on the concrete? Otherwise, you would get thermal bridges (condensation) between the plaster and the concrete wall? In other words: The plaster will assume the temperature of the concrete? Do you have heating additionally installed? Or do you only want to increase the temperature through insulation? Our basement is 18 degrees without heating due to the external insulation. Inside, there are raw concrete walls. If everything works for you and you manage to increase the temperature by 3-4 degrees, I might put Thermoputz on mine too

First of all, thanks for the quick exchange of opinions,

- Yes, Thermoputz lies fully on the concrete wall.
- I think condensation between the plaster and the concrete wall is unlikely.
- No, I do not have heating yet, but I will install underfloor heating in the end.
I want to have 21 degrees.

Regards
Energy-core

I am not familiar with the idea of [Thermoputz]. I used insulation boards for my place and glued them fully to the concrete wall. This also has to be done airtight.