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?
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.
Great 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
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
7/16" osb I have nothing against it...
2x4, well your much better off loosing 2" on the studs and gaining it in the
(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
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.
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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