i recently completed anaddition with cathedral celings. I noticed that during wet and cold weather water was dripping drom the soffit vents.
the ceiling is unfinished at this point and i pulled back the insulation
and most of the underside of the roof deck is wet. because of the extent of the moisture i dont think the roof is leaking.all the insulation was wet. i had also installed some air channels and it was wet inside them too.
1) is r-19 too thick for 2×6 rafters as it seemed to be touching the decking?
2) because the ceiling is unfinished so far is the heat getting past the insulation and condensing?
3) would a vapor barrier help?
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what is the foundation / floor system ? concrete slab.. crawl space ?
a vapor barrier would help.. but it is more important to find the source of all that water .. did you insulate right away... before the moisture level dropped to equilibrium ?
and the vents.. do you have a ridge vent ? i know you have "air channels " are they continuous from the soffits to the ridge ?
Mike Smith Rhode Island : Design / Build / Repair / Restore
If I am reading this right…………..
1- You don't state whether FG insulation is faced or unfaced, but you did state that no vapor barrier exists and I presume that no drywall or the like is place either. Sounds to me like water vapor is virtually unfettered in making its way to the insulation and the roof decking. Not good. The decking is cold up there and water vapor is naturally going to condense on it.
2- I presume you haven't installed channels all the way to the ridge as you stated that the insulation is touching the decking………this is far from ideal. The insulation is blocking the necessary air flow. IMO, I wouldn't be inclined to run channel vents all the way thru as this wouldn't allow for the best air flow to the insulation itself and you need to get it dried outand keep it that way in the future……… but the insulation must be withdrawn in some manner so as not to touch the decking. Then air can move thru there……..in each and every bay, as it should.
3- We know not what you have for "top end" venting, i.e., ridge or pan vents. In this situation, I think a ridge vent will serve you best.
Yes, IMO a vapor barrier would definitely help in the short and long term, but only after you get that insulation pulled back from the decking and insure that a ridge vent is in place. You need to get things dried out and keep them that way. I would provide for the aforementioned ASAP and then get a finished ceiling in there.
Much as I hate to say it, I think you may be in for insulation removal and a reconfigure to get a handle on this.
Sbluesixus,
Cathedral ceilings only work when there is an impeccable air barrier at the ceiling plane. It sounds like your ceiling is not installed yet. You will be plagued with condensation problems until your ceiling is installed, especially if you are trying to heat the place. So install your ceiling quickly -- and be sure the air barrier is impeccable. (Don't install tongue-and-groove boards, for instance, unless you install drywall first.) Be careful of all penetrations of the finish ceiling: at partition top plates, plumbing vents, and electrical boxes. Use caulk, gaskets, and spray foam to stop all air. Once your ceiling is installed, you're almost done addressing your problem. Now look around for sources of interior moisture. High interior moisture may be due to normal construction -- drying concrete and drywall mud. Usually things settle down into a normal range after a year or so.