Interior vapour barrier and exterior rigid foam
Hi, just looking for some help on a home reno and any help would be greatly appreciated.
I’m doing my siding with fiber cement on a bungalow in Regina, Saskatchewan (Zone 7). The walls are 2×4 with roxul insulation and a 6-mil poly vapour barrier on the inside. Originally I had built the windows out to fit 1 inch EPS foam (Silverboardxs). Now that I’ve been looking into it I could see possible moisture problems from this.
If I use 1 inch EPS the dew point will be inside the wall however it will be more breathable from the exterior. Whereas, if I do 2 inch EPS it should move the dew point out, however it will create more of a double vapour barrier. I can work the trim to still look good around the windows using 2 inch EPS, however 1 inch would be less work.
Which would be the best way to go or is there another solution I’m not thinking of?
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