Is PU foam harmful to the vapor barrier?

Hello everyone,

I have a question: is PU foam harmful to the vapor barrier membrane?
In our case, the vapor barrier (see green marking in the attachment) was glued to the bottom of the ring beam with a bead of adhesive.

We insulated the cavity between the threshold and the interior with Styrofoam, and the gaps (between Styrofoam and membrane and between Styrofoam and ring beam - see red marking) were filled with PU foam.

The question now is whether this was a good approach or if the PU foam causes problems when in contact with the membrane?

Best regards and thanks
Hannes

Mineral wool, stone wool, wood wool or similar belongs in there and not EPS... Apart from that, it does not harm the vapor barrier.

Hi ,

why no EPS? What speaks against it here?

Well, as you noticed yourself, that was an awkward patching and fiddling, then there were cavities that had to be foamed, etc. It should be clear that this is not in the spirit of the inventor. For this, there are flexible insulating materials and preferably also moisture-regulating ones like wood/hemp or similar.

Fortunately, it was not lumpy. We were able to cut it in at the correct angle directly with a hot wire. PU foam in my opinion was not necessary, but now it should be 100% (it's already sealed anyway because the vapor barrier is behind it). With mineral wool, I would have asked myself how to plaster it cleanly? The ring beam already had Styrodur from the shell builder and with the EPS on top, we can now easily apply a mesh and then plaster.

There are plaster carriers made of the materials. But okay, if there is already EPS underneath and a mesh is integrated and plastered, then that’s fine.