Spray or rigid foam to convert to conditioned attic in California?
Home in climate zone 3c (SF Bay peninsula), built in 1952. I am the home owner.
I had the roof replaced last year, and converting to a conditioned attic was always part of the plan (so that the ducts are inside the envelope). To that end, I used Hunter Cool-Vent panels over the roof deck. The roof assembly is as follows:
– OSB over the rafters
– 3.5 inch Hunter CoolVent panels (with R-11 rigid foam, then an air gap, then OSB)
– A fire rated underlayment (not sure which product)
– Standing seam metal roof
My rafters are unfortunately 2×4, so I had assumed that the best way to get to R-38 (even with the rigid foam on top) is to use closed cell SPF between and under the rafters.
However due to concerns about an undetectable, and untreatable termite infestation in the future (my understanding is that termites can chew through foam), I am now double-guessing this plan.
An alternative (suggested by the termite company) is to use 3.5 inch rigid foam between the rafters, then another couple inches of rigid foam under the rafters, then something like Fi-Foil Silver Shield.
Is this a reasonable plan? Are my concerns about termites with SPF warranted? Which route would you recommend?
Thanks in advance
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The concern of termites chewing through the foam to get to the wood has validity. AND, that would be for BOTH rigid and spray foams. Maybe I’m biased from all my good times in SF, but I didn’t know termites were/are a thing out there. In any case, I’m guessing the foil would act as a termite “shield”? If so, it seems that could be installed over either foam type, albeit leaving air pockets under the spray foam. However, something tells me this foil product might not keep the critters from getting their din-din. Maybe look at a treated foam board like this one: https://nisuscorp.com/product/bora-foam#:~:text=BORA%252DFOAM%C2%AE%2520is%2520polystyrene,liner%2520directly%2520to%2520the%2520board. I’m guessing there are also products to treat the wood prior to insulating it. But even then, couldn’t the termites get to the wood via the air gap in the panels? Sorry if I’m only adding more anxiety and/or questions to your process! (My wife says I’m very good at that…)
Thanks for your input. Yes, termites are very much a thing here. I think he suggested rigid foam + foil because it's removable (for termite treatment), not because it's some kind of termite shield.
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I should also mention that I'm having the rafters and roof deck treated (preemptively) with BoraCare before insulation (whether it's foam or rigid)
What's the foil for then? Otherwise assembly seems fine.
Can't termites chew thru anything to get to wood (food)?
Wouldn't anything that is removable create a potential issue with air sealing?
Here is a product I have used for a different purpose that might be useful ...
https://gapogroup.com/