Interior insulation of concrete wall

[daysconfused]

Hello,
I live in a split-level house. Part of the basement is a warm space, as shown in the picture. That part is mostly below ground and is insulated externally with Isodrän, but I have no internal insulation. Then I have a cold space where I now plan to install an IR sauna. Since I assume the IR sauna should stand in a relatively warm space, I thought of dividing the cold space as shown in the picture and insulating the room where the sauna will stand and possibly installing a heater.

How do I insulate internally against the concrete wall in the best way? What material should I use and what construction should I have?

I've only insulated plank frames before and then had the following layers: external panel, wind protection foil, insulation, construction board, internal insulation, vapor barrier, drywall.

But I assume, for example, that I don't need any wind protection foil against a concrete wall.

 

[noone70]

I am working on a similar project and will probably use PU foam. Steel studs, foam, and then drywall (possibly OSB under the drywall). Nothing else is needed.

However, it's difficult to make it economical if you want the surface spray-insulated when there are smaller areas to foam. Still, I found a do-it-yourself product that I intend to try: http://www.isopol.se/byggnadsisolering/

It consists of two components that you mix together and then pour into the space to be insulated, where it slowly expands and fills the space.

 

[daysconfused]

Thank you for the response. It's worth considering, but in that case, I should, just like you, do it myself otherwise it doesn't pay off, I feel. But doesn't it work just as well with cellplast sheets in that case? It might not be as tight, but it feels significantly easier.

 

[noone70]

Thanks for the answer. It's worth considering, but in that case, I should, just like you, do it myself because otherwise it's not worth it, I feel. But doesn't it work just as well with foam board in such cases? It might not be as tight, but it feels significantly easier.

No, it creates quite significant thermal bridges. Before I found the pu foam, the plan was to use foam board with beveled edges. I planned to put them on the wall and then on top of that 45 metal studs. It's better than nothing but far from the same as foam.