can i get some input on what layers to use on a new (eco-ish) construction in cold canada? i am thinking of (from outside to inside) siding, firring, 1"rigid foam, 7/16"osb, 2x6 with white fibreglass insulation, reflective vapor barrier, firring, drywall. do i need typar outside?
also how common is it for mice to eat through PEX pipe? common enough that i should go for copper?
What's with all the firring? I would use the house wrap, and if you're trying to go eco-ish, skip the fiberglass and go with cellulose.
I've never heard of mice eating PEX, but I guess if they're hungry enough. The mice around here prefer PVC.
Never heard of mice eating through pex.
I agree that cellulose is a good idea. I also think firring is a good idea. It will help prevent out of plane issues with butt joints, and if you are using cedar, it will prevent cupping which is a problem with cedar on foam. Building paper is optional IMO. It can be another insurance layer for water intrusions, but you could also use strips of it as sort of z flashing at the top of every horizontal seam. Haven't really heard much about a reflective barrier inside, but i imagine it would help.
Firring creates an airspace so that the radiant barrier can do its jobs. Without an airspace, the conductive heat transfer dominates, so the radiant barrier is pointless.
Cheers, Wayne
Foamboard outside can trap moisture in the fiberglass insulation, it could mold.
Visit the Building Science web site and do whatever they recommend.
RGreat idea, but better idea would be siding, firring, 2" rigid foam, water/air barrier, 7/16" osb (air sealed at seams and ends), 2x4 with closed cell foam, glued drywall to studs and plates.
Siding offers rain,uv,mechanical protection but is not water proof. If your using vinyl for siding, you dont need the firring.
2" of rigid foam is R-20 and the kicker is there wont be any thermal bridging on the studs. (keep the joints tight or even better use 2 layers 1" stagger the seams) 2" of foam at R-20, would also keep the dew point exterior of the water/air barrier 7/16" osb I have nothing against it... 2x4, well your much better off loosing 2" on the studs and gaining it in the insulation.... (you still get to use windows and doors with 2x6 Jambs !) 4" dence pack cellulose is great for air sealing and offers a high R but the best you can get if you can afford it is closed cell foam, hell there is nothing better. Gluing the rock to the studs, top and bottom plates helps prevent air infiltration.Pay special attention to air infiltration, keep that to a minimum, but always always supply ventialtion, choose an HRV or an ERV at the least get exaust fan on a timer.
Glenn
Good idea thinking it through ahead of time. 2" rigid foam outside makes window and door installation more difficult. Firring out the flanges just completes a convective path for heat loss, and you can't nail the flanges to the foam! We use 5/8" R-5 rigid here as an add on protection, but we have to fir out the windows and doors. On the inside, have you considered Icynene? The performance is far superior to glass. A near pefect seal. It is best suited for new construction. It's also a very green product. There are other generic brands out there as well. We build dozens of Energy Star houses and a few LEED houses, all of which specify Icynene-type foam insulation, although the LEED's people seem to prefer fiberglass in the roof part, due to moisture concerns.
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