Re: Moisture in exterior side of wall
That's not the role of the vapour barrier.
Originally Posted by Greenmtn
The barriers role is to prevent vapour entering the wall cavity and condensing --- such as you've discovered.
It's hard to say what the discoloration you see on the insulation. It may actually be dirt which indicates there is moving air happening within the wall cavity.
Somewhere there is a break in the vapour barrier and as a guess it may be behind the tub. It's not uncommon to find the vapour barrier isn't properly sealed to the wall behind the tub.
Another place is the ceiling to wall joint of the vapour barrier ---- if the ceiling has an attic directly above.
The fact there isn't a bath exhaust fan contributes to an increase of vapour drive from the increased moisture in the bathroom.
"" an ounce of perception -- a pound of obscure "