Building assembly error
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Hi all,
I’m a contractor in southeastern Ontario, Canada, in Zone 6. About 5 years ago I rebuilt my own house, an old farmhouse with some very poorly built additions, and in the youth of my career did what I thought was a good quality retrofit. I replaced rotted sheathing, taped the seams, added R5 foam on the exterior, a rain screen, and cedar siding. We have vaulted ceilings and I spray foamed the roof, which is metal on the exterior, though not very well done.
I did not however use an interior vapor barrier because of my impermeable exterior insulation. These days I use the ProClima system with Intello, Rockwool and Mento, but back then I was worried about trapping moisture. I think I even posted on this forum and got some advice not to have an exterior vapor barrier, because the assembly has to be perfect otherwise condensation can occur.
I am now wondering how to fix this mistake, mostly with air quality/ mold growth in mind. The more homes I have renovated the more mold and rot I have seen and the less I trust my system in my own house.
I can imagine pulling down the drywall and adding Intello to the studs, but I suppose I could also just add the Intello directly to the drywall and add a second layer. I guess I see no easy solution so am looking for the least worst solution. Removing the siding, rain screen, and exterior insulation would be the least favorable option, both time and cost wise .
Whatever happens a re-roofing is in my future, as I want to make sure I’m not introducing any excess moisture to the walls/ roof.
Any ideas, would be appreciated!
Spencer
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Replies
What type of foam did you use on your walls? If XPS or unfaced EPS, you will probably be fine--they are both permeable enough to allow drying to the exterior, especially when there is a rain screen.
Have you done a blower door test? The tighter your house is, the less likely you are to have moisture accumulation.
Do you monitor your indoor relative humidity? Keeping it below 50% or so will help keep your walls dry.
Do you use air conditioning in the summer? That will help dry any moisture that accumulates over the spring season, when vapor drive to the exterior is weak.
If you don't use air conditioning or plan to use it in the future, you could paint the walls with vapor-retarding paint.