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Firestone ISO-R foam. 1″ R value? Worth keeping?

Canadan | Posted in Green Products and Materials on

The previous owners had our house (1957 bungalow in Zone 7) wrapped with 1″ Firestone ISO-R foam and then vinyl siding nailed onto the foam.

Not only is 1″ not enough for zone 7, the contractor just laid the foam directly over the old cedar siding, as far as I can tell this is useless because of the giant air space behind the foam.

I’m in the process of stripping the exterior to the wood plank sheathing and planning to add 2″ of foam to achieve the R-10 required.

I’m wondering if this foam is worth re-using? It seems like a nice product but I can’t find any information on its R value or if this is its intended purpose. It has a foil back if that matters?

I’d put up 2 layers with the seams offset and taped. to get the required R value for this zone if its R5

Thanks in advance for any information on this product. Here are some pics.

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  1. user-4053553 | | #1

    Fascinating, you could e-mail firestone and let them tell you they have no idea, i would personally toss it but if its in good condition you could put it on top of your new foam for fun.
    Perhaps you should just donate it to habitat for humanity if you have a local store (or any reuse store) and maybe someone out there will find a use for it.
    If i were you i would go for a lot more then R10 though, if your already doing all the work now there will never be a cheaper time to add more Rs.

  2. Canadan | | #2

    Hi Alan, thanks very much for the reply. I recently gutted our basement, so I might glue it to the exterior concrete walls before framing the interior. If, of course, it won't off-gas or something.

    I agree, more than R10 would be much wiser decision, but i'm limited to thickness because we're siding the house in hardie plank. I plan to do one continuous layer of 1/2" foamular (R3) and then a continuous layer of 1 1/2" insul-pink (R7.5) because it has channels cut in it for the furring strips.

    Not ideal, but should help keep the house warm and meet the GBA recommendations for Zone 7.

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