Question

We have an intermittant 3'x5' wet spot that occurs on our condo living room ceiling above a SW bay window. There is a bedroom above the living room. There is not any plumbing or heating ducts in the area. The spot occurs about 5' from the outside wall. It does not appear to be weather related. Extensive caulking has been done to the siding above the window to no avail. I opened the ceiling on both sides of the 2x12 joist in the area that gets the most moist. The joist run parallel to the outside wall.There may be damp spots(??) on the joist and the 2x4's coming up from the outer wall. On the window side of the joist only, there is a vapor barrier & about six inches of insulation that is dry. There is not any insulation on the living room side. When present, the wet spot is on both sides of the joist. Have been told this is a condensation issue related to improper insulation. Your opinion please and how do we fix the problem? Thank you for your help. Darrel & Rachael