Zone 7 (Saskatchewan) need help with selecting an energy effective wall will proper air sealing
I have been reading through this site for a couple of years now and I must admit that I am somewhat more confused now than when I started out.
We are building a new house in Saskatchewan (Zone 7B I think) and we were hoping to add a bunch of extra insulation and at the same time employe some advanced air sealing techniques. However, we will be working with a builder who is familiar with building to code which in our province means 2×6 walls with cavity R20ish (not effective) insulation and an interior poly vapour / air barrier.
I understand that the code is poor and I want to build a better house than this code prescribes. However, I don’t want to get in to trouble with my builder trying to instruct him to do things that he is (a) not familiar with and (b) lacks knowledge with. I am worried that I will end up with a problem house.
Our priorities are air tight and as much insulation as feasibly possible. I have been leaning towards a 2×6 wall with some sort of batt or dense pack cavity insulation and 2 – 4 inches of continuous rigid foam on the exterior. My builder should be able to handle this as he has built homes with 1″ exterior foam in the past so I am hoping he can extrapolate to 2 layers of 2″ but I am concerned about all the detailing especially windows and doors. I am especially concerned about air sealing and moisture in the walls as my builder only know interior poly behind the drywall acting as both air and vapour barrier.
I hate the concept of using poly behind the drywall for many reasons. My main concern is that the poly is never tight given all the screws and penetrations that go through it. And if I wrap with exterior foam (2 layers) thereby limiting my wall’s ability to dry to the outside am I just opening myself up to problems given that moisture will get through from the inside but at the same time the interior poly will greatly reduce the walls ability to dry to the inside.
I guess my real question to the community is what would you do if you were in my shoes. Keep in mind that I am limited to choice of builder so getting a builder out to my site with knowledge of thick tight walls is probably not an option. Would it be safe to ask my builder to give me a 2×6 wall with R2x cavity insulation and 2 layers of 2″ rigid exterior foam knowing that he is probably not going to build the tightest walls?
Thanks for you interest and opinions.
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