Non foil faced polyiso
Building a new house in Southern California (climate zone 3). House is single story and about 5,000 sq. ft., so there is considerable wall square footage.
The walls will be:
1. airtight drywall (it probably won’t be perfect, but hopefully pretty good)
4. plywood or OSB (depending if it is a shearwall)
5. possibly 1″ polyiso (depends on the responses to this post)
6. Tyvek type material (still reading whether it’s better on top of plywood or on top of foam insulation). If i use foil and tape all the seams – I may not need Tyvek???
7. 1×3 to hold the polyiso and siding.
8. James Hardie type cement siding
I have looked at some used polyiso which is not foil-faced. This used polyiso (no foil) will be about $3,750 and the new (with foil) will be about $5500. The way I understand it the used polyiso will be have holes from the original screws/nails – is this an issue? I suspect in my area where we use A/C more than heat and it regularly gets to over 100 degrees in the summer the foil is important. Though I live in climate zone 3, I live in one of the hotter areas of the zone.
How important is the foil facing on the polyiso in climate zone 3?
For the amount of money the polyiso costs, is it even worth doing in zone 3?
Does anyone know of any building code which prohibits used polyiso? (This project is in the city of LA – strict codes)?
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