Vapor barrier between underfloor heating and dry screed?

Hello!

I have read countless posts but still didn't quite understand.

At our place, the following floor structure is applied on the uninsulated basement ceiling:

- 3 cm EPS insulation
- Underfloor heating with Rehau TS-14 panels
- Knauf Brior 18mm dry screed

Now my question. Should there be a vapor barrier between the underfloor heating elements and the dry screed?

Best regards, Martin

Nope. What is it supposed to achieve there?

Thank you for your response.

So nothing necessary, even though the unheated basement is below?

The vapor barrier is intended to prevent condensation from forming in the insulation. For this to happen at all, the temperature within the construction must drop below the dew point. However, this is impossible in the immediate vicinity of the underfloor heating pipes. And even if, due to some crazy circumstances, this should ever occur, EPS (unlike, for example, mineral wool in the roof) hardly absorbs any water, so it does not lose its insulating effect due to some moisture. And mold cannot really develop there either, due to the lack of organic materials. Ergo: No vapor barrier necessary.