vapor barriers

I hired what I thought was experienced metal roof installers- it was a complete take off and rebuild with a t/g exposed plank interior on 4' center beams. The install included 3/4" pine, R39 of foam insulation (one layer foil backed), 2x4 layed flat screwed through to the beams, 3/4 " osb, frost guard them my metal roof. THe original plan had a vapor barrier over the pine. When I returned home one night I noticed the roll of vapor barrier had not been used. The installer indicated it wasn't needed with all that insulation. The supplier agreed with him. The following winter I am getting water on warm days leaking through the pine on 4 ft centers. I got out the photos my son took during the construction and found that the 2" foam sheets were not overlapped but the seam goes all the way through to the 1 1/2 " air space between the 2 x 4. What do you suggest for a fix?

Sorry to hear about your roof issues. I would first want to see what the humidity levels inside the home are but you description of how the roof and insulation were applied has me worried. The reason that we run Ice/Water in these applications is because it is just to easy to have air leaks with T&G decking. While the foam board would provide sufficient vapor retarding, the fact that the deck is inconsistent makes getting that seal difficult (even if the foam is lapped properly). Not lapping and staggering the joints is another issue and you probably are getting some air loss and resultant condensation. I fear the only way to really fix the issue is to yank the roof off or seal it from the underside. Sealing it from the underside (if by paint or similar) often steals from the look that T&G gives.