I am in the process of adding a larger exhaust fan. I have had a problem with mildew and failing drywall joints, and hence the upgrade. As I am removing the ceiling (as to vent the fan through the roof, and not the wall) I noticed that underneath the drywall was a layer of Tyvek. The bathroom sits on the second floor - there is no attic space so above the bathroom ceiling is simply insulation and the roof.
Should the Tyvek be there in the first place? It is my understnading that Tyvek is not a vapor barrier, but a wind barrier. It is doing any harm by being there, that is by allowing vapor to enter into the insulation cavity? Should this be replaced with a 6 mil vapor barrier? I do intend to gut and remodel the BR at a later date.
Thanks for any insight.