ᐅ Vapor barrier between underfloor heating and dry screed?

Hello!

I have read countless posts but still am not quite sure.

In our case, the following floor structure is installed on top of the uninsulated basement ceiling:

- 3 cm EPS insulation (1 inch)
- Underfloor heating with Rehau TS-14 panels
- Knauf Brior 18 mm (0.7 inch) dry screed

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

Best regards,
Martin

No. What effect would it have there?

Thank you for your response.

So nothing is necessary, even though there is an unheated basement underneath?

The vapor retarder is intended to prevent condensation within the insulation. For condensation to occur, the temperature inside the construction must drop below the dew point. However, this is impossible near the underfloor heating pipes.
And even if, due to some unusual circumstances, it did happen, EPS (unlike mineral wool used in roofs, for example) absorbs very little water and therefore does not lose its insulating properties when exposed to some moisture. Additionally, mold cannot really develop there either, due to the lack of organic material.
Therefore: No vapor retarder is necessary.