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benbern125 03-01-2011 06:49 PM

Condensation on cathedral roof being remodeled
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I am admittedly new to the forum and I've read other forums on condensing at the ceiling interface, but nothing I felt that applied to my situation. Here we go:

I've recently inherited my mother's house and ripped down all of the ceiling tiles and drywall to remodel. The home has cathedral ceilings (in other words, the outer tar and gravel roof, tongue and groove wood planks, a 2x10, and tongue and groove on the inside ,in that order). The old insulation in the roof was worn down and settled beyond salvage, so in the course of electrical we cut misc. holes in the tongue and groove to pull out the old insulation and install new R-19 24" kraft faced batts.
Let me also mention that I've also removed the A/C unit and heater
We were so excited so finally finish electrical! I don't have the time to do the drywall so I have contracted it out.
Well, when they were installing the drywall they called me over to tell me some of the insulation was wet. I was curious as to if it was a roof leak or condensation, so I went on the roof with a hose and soaked the entire area at all different angles for an hour. No leak. It rained the next day, no leak. So I told them to button up the roof and move on, that it must just be a small amount of condensation.
The contractors call me today and tell me that the beams (three 2x10s that runs horizontally throughout the house that the rafter 2x10s are nailed to) were wet and it was making the drywall wet. I went on the roof and checked and some of the tar and gravel was loose, but not enough to soak end to end of the house (~75ft). I've attached a picture of one of the wet spots, but there are at least 5 of these spots in different places on the ridge of the roof in different rooms spanning the entire middle beams of the house.
These are my thoughts:
1, There are soffit vents but no ridge vent - doesn't this counteract the ideas of either venting the attic (would need a ridge vent) or unvented attic (with the soffit vents)?
2. I'm thinking if there were any roof leak we would have noticed that amount of water when the drywall was down (for about 3 months while we were doing the electrical).
3. If it is in fact condensation, will an a/c dehumidifying the air change this problem?
Any help is appreciated!! i have pictures of the wet spots if this would help.
By the way, I am in South Louisiana.

nealtw 03-01-2011 07:22 PM

If this house was built today there would be 2x4 strapping above the 2x10s to allow for venting above the insulation. Without the strapping you will requir air gap between insulation and roof sheeting and a ridge vent to vent every bay.
That dosn't explain how it worked before you took it apart, if you have roof leak water can travel in strange ways and show up anywhere.
Compare what you took out to what you put in, there might be a clue there.

benbern125 03-01-2011 07:32 PM

Thanks for the quick reply. I'm just dumbfounded by the water appearing.
That was the main reason that I put r-19 instread of something like R-30 - to leave an air gap, which is technically there with only 6.5" of insulation in a 10" gap. This is what's making me think to cut in a ridge vent.
But could I rid myself of this problem by covering the soffit vents? Will an unvented airgap work to get rid of the high humidity air? I've read there are two types of air gaps for low roofs like mine: vented and unvented. I'm just wondering how well the unvented will work...

oldognewtrick 03-01-2011 07:59 PM

Were the drywall guys by chance running a propane heater while they were working?

benbern125 03-02-2011 09:07 AM

Hey oldog,
No, they weren't running a heater and there is no A/C or heater installed in the house. There have been no "extreme" temperatures here over the last week or two, just 50s to 70s... The pictures I've taken look more like puddled spots than an even spread across, in your experience does this lean towards condensation or leaking roof?

handyguys 03-02-2011 01:18 PM

Ugh - I think the problem may be compounded by going from R30 to R19.

You either need completely vented (air flow above each bay from soffit to ridge) or completely unvented and sealed against moisture (not fiberglass).

The unvented route, from what i have read, is usually best for a cathedral ceiling. Essentially you fill each bay with closed cell spray foam. This acts as a moisture barrior and provides max insulation. If the drywall isnt finished yet I would have your guys pull it down and then have a spray foam guy fill the bays and forget any venting. Problem solved (unless it is indeed a roof leak).

Good luck.

oldognewtrick 03-02-2011 04:57 PM

Is there by chance a chimney or wall near by?

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