Pre-insulation jitters: condensation on interior side of sheathing
Zone 6/7. Calgary. Weather has been below freezing for two weeks straight.
I am concerned because we have been heating the house using portable heat to about 5°C, which in this cold weather is causing condensation and frost to buildup on the interior side of sheathing.
we are ready to begin insulating, but I am wondering if this amount of moisture will ever dry if we continue without doing something about it.
wall stacks up like this:
drywall
6mil poly
r20 fibreglass batt (I’m worried about this getting wet and never drying out)
3/4” sheathing
tyvek
3” rockwool (to be installed after interior work is underway)
rainscreen
wood siding
as you can see, the wall will be able to dry to the exterior, but I’m concerned this amount of moisture is asking for trouble.
what would you do? Wait for warmer weather? Install rockwool now and heat the house till the sheathing dries?
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Replies
See photo attached
Some other options:
1) use a heater that doesn't add moisture to the air
2) turn the heater off for long enough to get rid of most of the moisture accumulation and then turn it back on and work fast.
In case you haven't read this: https://www.greenbuildingadvisor.com/article/condensation-wall-sheathing-construction
Seeing as you're putting up exterior insulation anyways, that option does seem like a sure and easy way to remedy the problem, assuming the sequencing of doing that first isn't a real deal-breaker.
Is that a slab?
Perhaps a high powered fan blowing on the sheathing could help bring that moisture back into the air. Even better if coupled with a non-humidity introducing heater.
Also wondering if your sheathing is air-tight? It almost looks like the moisture is riding air through sheathing joints?
Thanks Tyler, for pointing out that article. Hadn’t seen it, and it looks like my question is a duplicate to these situations. The only difference is that I intend to install rockwool on the exterior - I just didn’t realize it would be an issue to do it after the interior is done.
The sheathing is not air tight. This is basically a huge gut renovation where we kept some of the original exterior walls, and those walls are sheeted with 1x8 shiplap. So, without covering with another layer of sheathing, it’s impossible to air seal it. (Which seemed like a huge waste of materials and resources at the time)
I’m going to first switch from NG heat to electric, along with allowing the house to stay cooler. Hopefully we can see some difference in the amount of condensation by doing that.
But I may have to consider pausing the interior insulating and switching gears to the exterior.