Replacing R7 in exterior home walls

Question

I really appreciate all the great feedback from the forum members on various questions.

We are working on lots of renovations to our home that is located in Toronto, Canada. It was built in the early 70s and the external walls are built 2x4 studs with Gyproc sheathing, 1/2" air gap and 4" brick veneer. On the inside there is 1/2" drywall, no vapour barrier and R7 fiberglass insulation with kraft paper facing. Pictures included below.

We needed to open many of the exterior walls for the renos but not all. However it appears that R7 is no longer adequate in terms of insulation so we bit the bullet and asked the contractor to open up all exterior walls to replace insulation everywhere.

What insulation should we be replacing with? Some of the insulation that was removed from walls has black markings. Is this of concern or point to a possible issue?

Any pointers from the experts would be very helpful. Thanks

Answer 1

R15 is the best you can do in fiberglass and mineral wool for a 2*4 wall. Iirc you could get close to R-30 with closed cell spray foam, but that's $$$.

That black is probably dust. Unless you see black staining on the studs where it was removed from its probably not a sign of a serious problem. Still, it suggests that your wall voids are not air-tight, which probably increases the flow of heat through the wall. Now is a good time to seal them up tight. A bead of polyurethane spray foam (name brand is Great Stuff, but generics are good too) along the corner of the studs to the sheathing is what I did for my house. Try not to get it on your hands, clothes, or carpet - it sticks to everything and is difficult to remove once it cures.

The paper facing on your insulation is sufficient enough as a vapor barrier for most cases.

Answer 2

The black is dust that is deposited by air leaks.

The best building framework is passive house and the perfect wall which orders your priorities. The first is liquid water, the seconds is air, the third is vapor and the last is insulation.

If you've gone to the trouble to open all the exterior walls to increase your insulation, I am going to assume that budget isn't the top priority.

I'd get aerobarrier to give you a quote for air sealing. https://aerobarrier.net

Once it was airsealed. I'd go with roxul for insulation. A passive house membrane like intello on the warm side of the insulation for moisture barrier. Then drywall like normal.

Big project, good luck !