Continuous insulation – polyiso foiled both sides
I have read numerous articles on here but cannot find the exact procedure that I am about to undertake, which is polyiso (Carlisle) 2” thick foiled both sides of sheet over a 2×4 wall with out wood sheathing, Simpson 20g L brackets for BWL.
Austin, TX Zone-3
R-10 Polyiso 2” foiled both sides over 2×4 with out wood sheathing. Continuous sheathing so will be taped/ sealed exterior. Fiber cement board attached through the Rigid Foam/polyiso with a 3/4” strapping. Cavity insulation will be R-13. Gyp board interior with either latex paint and sealed edges or more breathable approach Lime wash type paint. (Need some more research on the last part)
Concern and Question:
I was originally looking for a polyiso foil faced on one side so that if any vapor transmission happened and hit the dew point then moisture would be able to escape… or if there’s any water penetration for what ever reason (things happen over time).
The problem is I am running on a tight schedule to get the structure up and only place in town I found with the correct thickness only has a 2 sided foil faced Polyiso. About to pull the trigger but trying to hold my self back if I use the double sided foil face, will I lead into issues for moisture not to escape?
From my research, since the structure is 2×4 wall with R-13 batt insulation in cavities along with the R-10 Polyiso to the exterior then I really shouldn’t have to worry about hitting the dew point for where I’m located.
Am I correct in thinking this or should I just hold out and find a single foil face polyiso?
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