Roxul / foam EIFS wall system in zone 6A (Canada) - vapour barrier placement
I am working on a house plan for approx. 1800 s.f. The views appear well suited to mostly passive solar with some windows (dining and 3 bedrooms) facing east.
For the wall assembly I am proposing (outside in)
1x3 furring strips
4" of foil-faced polyiso foam board (est value R6 per inch or R24, taped and sealed.
2x6 wall on 24" OC with Roxul R22 cavity insulation
Total installed R value: R46.
based on average winter temperature of -10C or 14F I calculate and inside temp/humidity of 70F / 35% i calculate:
delta T = 56
insulation distribution inside/outside = R22 / R46 = 0.478
Temp @ sheathing = 70 - deltaT x 0.478 = 43.22
based on psychrometric reading dewpoint is at 40F.
Is this a good enough cushion to warrant vapour barrier @ the polyiso sheeting level, or should I be using:
-Less interior insulation (ie R14)
-more exterior insulation (ie 5-6" foam)
-a different (vapour permeable) foam sheathing and a poly vapour barrier behind the sheetrock?
Any help appreciated !
Posted Tue, 02/04/2014 - 01:49
Edited Tue, 02/04/2014 - 10:05
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