Vapor and air barrier for continuous insulation retrofit
I am planning an energy retrofit as prescribed by an energy evaluation. My 1993 two-story home needs continuous insulation added and I am struggling to find recommendations on an appropriate WRB that can also serve as my air barrier.
The house is 2×6 framed with fiberglass batts (R-17.3 effective) and poly vapor barrier which is not taped (and even found to be missing on one basement wall!) and the sheathing is 1/2″ ply. I am in Western Canada (Zone 5-6) and my energy evaluation has spec’d adding R-11.1 continuous insulation. I will be using 3″ of comfortboard for R-12.6. I’ve read up on dew point and also used a calculator to find indeed my dew point will be outside the sheathing.
Researching on GBA has led me to understand that I need a WRB that can allow this old construction to breathe, however, I also need this layer to become the definitive air barrier. One recommendation I found on GBA was
SOLITEX MENTO 1000 (38 perms). Speaking with a local builder building new homes with the same design as my retrofit (2×6 framed, combined WRB/air barrier, continuous insulation) I found they are using Siga Majvest (54 perms). Both products meet CAN/ULC-S741-08/ ASTM E2178 specs for air leakage.
Thanks for the help,
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