[Nomadicchefs]

I have noticed water dripping from around the inside flange of the bathroom exhaust unit. Around the edges of the flange it is discolored slightly. I took the flange off and noticed this white sheeting used. In the corners where it falls short or wasn't cut properly to fit together, that water either from outside or condensation is dripping into those gaps and running down inside the walls. In the pictures you can't see the dark spots, which I don't believe is mold but rather saturated wood. However, my question is what is this sheeting? I contacted keystone and they give me the run around, stating they can't divulge info over the phone due to liability. Seems insane they can't tell me where to get it, sell me some or what it actually is called. Any thoughts? It's winter with loads of snow here at the moment. No cracks on the outer dome, the seals are all good which is what makes me think it's condensation getting trapped in between the flange and wall somehow.