Zip R9 in Climate Zone 5
I’ve poured through this site and others in an attempt to decide on a wall system for a new house I am building. I’m in zone 5 (12572), the house is a simple gable box (4 walls + raised heel truss gable roof + full basement) with plan area of about 1,100 s.f. per floor – so modest size and simple massing. I am not shooting for any particular performance target, I am looking to get the best building I can for the relatively tight budget I’m on but no particular metric.
I am in the building industry and perhaps unduly biased (negatively) but I highly prefer to keep the detailing/system as simple as possible. I’ll buy a slightly less efficient system if it means its more likely to get done right.
Based on the above I had arrived at: clapboard siding (boral or cedar, tbd) + rainscreen (homeslicker or sim.) + zip R9 + 2×6 with rockwool batt. Air sealing will be the best I can draw and enforce within reason.
Despite a lot of reading I’m finding a hard time getting full comfort with the zip r9. From what I’ve been able to gather my ratio of batt to exterior rigid should be about safe (even with polyiso derated?). In the chance that there is condensation the back face is the polyiso not the osb, the back face of the osb seems relatively well protected. The rainscreen should give me a little extra insurance. I’m an engineer and not worried about the structural issues (or I should say I will sort them out). I see plenty of drawbacks with the zip r and I know it’s probably not the best R for my money – but I really like how it seems to involve very little atypical detailing and very easy to make sure it’s well executed. Is this a safe and reasonable assembly for my zone?
I would have expected this assembly/zone to have been beaten to death but I can’t find any good q&a or info on my setup in my zone. Any input on this assembly or pointing me to an article is appreciated.
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