Extra Vapor Barrier when you have Vapor Retarder in the Floor?

[pwb]

I am renovating a floor on top of an insulated crawl space. It will have hydronic underfloor heating and parquet flooring.

The construction is:
Subfloor panel
Cellulose insulation
Vapor retarder
Routed chipboard
Wood parquet flooring

I was just about to start on the parquet flooring when I read that all manufacturers seem to think there should be a vapor barrier directly under the parquet when you have underfloor heating. Should I have this even if I have a vapor retarder under the chipboard, or is the vapor retarder enough?

 

[Plupp 23608]

The parquet manufacturers require a vapor barrier, so yes. A vapor retarder is not sufficiently tight and is on the wrong side of the floor heating.

 

[pwb]

The parquet manufacturers require a vapor barrier, so yes. A vapor retarder is not sufficiently tight and on the wrong side of the underfloor heating.

They would both be under the underfloor heating. Between them is the routed chipboard.

But then I'll apply the vapor barrier. No risk of moisture getting trapped between the barrier and the retarder?

 

[Plupp 23608]

They would both be under the underfloor heating.

Your vapor barrier goes under the floorboards/underfloor heating, but the vapor barrier should be on top, under the parquet's impact sound insulation, alternatively a combination variant like Tuplex.

Between them are the grooved chipboards.

But then I put on the vapor barrier. Is there no risk that moisture gets trapped between the barrier and brake?

Normally, you don't put a vapor barrier/vapor brake in the floor construction, but as long as it is dry and ventilated in the crawl space, it probably won't do any harm.