Hi all,

I purchased a home a few months ago that had an interior renovation done last year. It has 2×6 wood framing and 4″ of closed cell Spray Foam in the wall cavities. Drywall for the interior finish and house wrap (Tyvek or similar) w/ vinyl siding on the exterior. I’m going to be replacing the siding this summer with Hardiepanel and could use some advice.

I’m looking to install some insulation on the exterior of the house wrap to add a thermal break. I’ve read articles about keeping a vapour-permeable layer on the outside when the inside insulation is closed cell Spray Foam, so I’m considering using Rockwool Comfortboard. I’d then screw some 1×4 strapping over the insulation (I believe it is a rainscreen) and have the Hardiepanel installed on the strapping. Would there be any issue with this set up from a standpoint of trapping moisture anywhere? Or is there a better insulation product I could use to add a thermal break.

Also the Hardiepanel rep I talked to last week recommended using Tyvek DrainWrap behind any insulation I’m adding over the sheathing. Does anyone see any issues with just stapling DrainWrap overtop of the existing housewrap or should I remove the existing first? Would having 2 layers trap moisture or is it alright?

I live in Alberta, Canada – zone 3 if that affects the installation at all.

Thanks so much for any help/advice on this!