PERSIST or modified PERSIST in Zone 4A?
I am building a small (800 sq ft) efficient cottage for my wife and I in SE Tennessee (4A zone). I own a tiny house building company and have a background in residential construction. The design is centered around simplicity, energy efficiency, and cost, but I am willing to spend a bit more money on things that will pay me back in the long run like a really well insulated envelope. It will be a simple A frame with metal roof and metal siding I am considering building a full on PERSIST method wall or at the very least adding 1″ of polyiso on the exterior. I have a few questions.
If I go the PERSIST route:
1. What foam type in walls/ceiling (I have a lead on some cheap polyiso)?
2. What thickness (R value) for walls/ ceiling in zone 4A?
3. Is going full monty PERSIST in 4A going to be cost effective compared to the option below when you factor energy cost savings (we are planning on owning this home for a long time).
4. Is there any specific implementation details I should follow with metal siding?
5. Is there any need for wall coverings on the interior with PERSIST or could I use the space for built-in shelves? As I understand it in the PERSIST method, more ventilation to the interior is a good thing.
6. Good cost effective vapor barrier to go on the outside of the bottom layer of sheathing.
If I go with 1″ foam exterior and fiberglass/mineral wool batt interior:
1. What thickness would I use for this? Seems like 1″ is adequate for my climate to ensure the dew point is not in the wall?
2. What are some good (cost effective) non-persist options for insulating a vaulted ceiling?
3. If I use foil-faced polyiso, do I still need a vapor barrier or housewrap?
In general I would also be interested in your insights about the pros and cons of how the two options compare in terms of cost and energy efficiency in zone 4A.
I will be chronicling the build on my personal website tallmantinyhouse.com
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