Insulate, uninsulate, vent, or?
Problem: water (condensation) dripping into master bedroom.
I’ve got an old New Englander in New Hampshire. I added an extensive shed dormer 6 years ago, when I bought the house, which added a foot of space to the upstairs but made that section of the roof almost flat. The low wall height meant the window headers had to be placed in the roof system, so the rafters and collar ties are hung off the headers, blocking those rafter bays from the soffit. Where the roof meets the wall, the R-30 insulation fills the space from strapping to roof. There is partial ridge venting (where it’s possible) and a small gable vent in each gable (3 total). There is 12″, tops, between the bottom of the ridge and the top of the collar ties.
The master bedroom, and only the master bedroom, hasn’t been finished. Two years ago I put a layer of 1″ foil-faced solid insulation on the ceiling, taped the joints and screwholes, but there are a few spaces (for various reasons) with no solid insulation/vapor barrier. The remainder of the house has a poly vapor barrier in the ceiling.
This week my wife noticed brown water dripping from a seam where the tape had loosened. I took out a section of foam. The fiberglass is wet (and brown) on the bottom, and the underside of the roof is wet (and frozen). It gets better (dryer/less stained) closer to the ridge; there are also drips outside. It appears to be confined to the area of the master bedroom, which is also where most of the rafter bays are blocked.
Should I:
1- take seal up the gaps in the foil-faced insulation?
2 – Drill some holes in the header and allow some soffit venting to the blocked rafter bays?
3 – Take down the foil insulation?
4 – Totally seal off the blocked bays and put solid or spray foam insulation directly onto the underside of the roof in the blocked bays instead of fiberglass?
5 – Something else?
Right now I’m leaning towards 1 & 4, but would appreciate more opinions.
Thanks,
N.
Replies
Greetings N,
As a first time poster Welcome to Breaktime.
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
"being human is a complicated proposition"-DavidxDoud
---Never show a fool a half finished job---Grampsy
I feel like a bunny in a hillbilly meadow at noon..........jjwalters
Thanks. After talking to a few (experienced and professional) people, I'm adding additional roof vents. The consensus is that there's just not enough venting now, and the bastardized hybrid nature of my roof makes it impossible to add more. Indications are that the problem is not the amount of moisture going out of the house (though the VB issue will be addressed); it's how ambient moisture gets trapped in the attic.
I've got my fingers crossed.
Thanks!
Take it all down and spray insulation is the best solution.
If this were a new job, I would say maybe yuou could just make sure to make that VB perfect.
But since this has been going on for some time and you have lots of water and staining, theere could be more problems than you can see, so it all needs to come down anyways to be redone.
And foaming it is a gauranteed way tobe sure it doesn't happen again.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Yeah, your basic choices are to make the roof "hotter" or "colder". Hotter -- foam insulation sprayed against the bottom of the roof might be appropriate if you were starting from scratch, but at this stage it would be better to go the opposite direction:
Add as much roof venting as you can manage, and seal up the inside vapor barrier as well as you can. Putting a plastic vapor barrier, carefully taped at all seams, over the foil faced would be the best choice for VB. (And, no, you don't end up with the dreaded "double vapor barrier" that way.)
I guess I don't follow what you're doing with the 1" foam. Is there more insulation above that? An inch of foam isn't very much.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Sorry; I wasn't very clear. There's either R-30 or R-38 fiberglass above the solid isocyanurate.