Retrofitting of underfloor heating in the basement room

There is ultra-thin insulation material and you could lay parquet on top of that.

Thanks for the tips. So the first step would be to supplement the floor. Can I simply lay insulation material on the existing tiles and then lay the parquet? Would a vapor barrier or something similar need to be installed?

you could install an infrared module e.g. on the ceiling;

What power would such an infrared heater approximately need (as said: insulated basement room, about 20 m2, about 2.20 m room height)?

But here we are talking about over 200 sqm

For me it's about 20 m2...

For me, it’s about 20m2

Yes, I just wanted to clarify that it also depends on the framework conditions.