Any issues with this wall assembly
Stationhouse
| Posted in Energy Efficiency and Durability on
New to this so excuse my ignorance. I recently build a house with the following 2 x 6 wall assembly. Exterior corrugated metal, strapping, 1″ aluminum faced poly iso(Energy Shield brand), tyvek with taped joints, osb sheathing, 2″ of 2 pound spray foam, R15 fibreglass batts followed with drywall. No 6mil poly used as I’m using the spray foam as my vapour barrier. I’m in Niagara Ontario, Canada and wondering if I’ll run into moisture issues/permeability concerns. Thanks.
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Replies
There is nothing technically wrong with your wall. The 2" of SPF +exterior rigid insulation is plenty for condensation control.
The 2" of SPF on the inside is not buying you much though, closed cell foam between studs barely increases the R value of the assembly because of the thermal briding of the studs.
If you wan air tight assembly, instead of SPF, go with taped sheathing with one of the more permeable exterior rigid foams (unfaced EPS or IKO EnerAir) and a warm side vapour barrier. This gives you pretty much the same assembly R value (~R2 less) for much less money without the high environmental footprint and install cost of the closed cell foam.
For the money you save on SPF you can even bump up the exterior rigid insulation a bit and get much higher assembly R value. High density 2x6 batts + 1.5" permeable polyiso is very good wall.
I like Akos's advice. You could also consider mineral wool for the exterior insulation to get even higher vapor permeability and lower moisture risk.