Adding exterior foam
I’m re-siding a large addition (built in 1988 by previous owner) to my 1890s home just north of Toronto, Canada (Climate zone 5A?) and plan to add some rigid foam on the exterior in the process.
The wall assembly consists of 2×6 walls filled with fibreglass batts with an interior poly barrier under the drywall. On the exterior it seems there is no structural sheathing or house wrap, just 1″ of XPS tacked to the studs. The seams in the XPS are not taped (!!!). Needless to say my home did not perform well on the blower door test I had done last spring.
I’m planning to remove the existing siding, tape the seams of the existing XPS, add a Tyvek WRB, then a 1.5″ layer of faced EPS over that and tape the seams, strap it, and side it. I think I’m in the right fluffy to rigid ratio to eliminate the condensing surface inside the foam sheathing, if that’s an issue.
I’m wondering about any concerns you folks might have with this approach. Should I add sheathing? With the interior poly barrier and the now taped XPS, wrap, and EPS am I creating a mould sandwich? How does my plan look?
I’m an avid reader and subscriber of the site and would appreciate any feedback.
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