Polyiso foam and fire safety
My house was built with foil faced polyiso exterior insulation under the siding. I live in a townhouse, and the siding is wood. I am worried that between those factors and the exterior insulation, the building might be rather flammable. There is one place where the foam insulation is exposed in the attic. It looks like they continued it there for convenience because the attic is unconditioned, so there’s no need for insulation there. Behind it is an exterior wall.
My question is, is it safe to leave this insulation exposed? I think not, because code requires an ignition barrier here, and I don’t think the foil facing counts. Printed on the foil it says something about how the product must be covered by sheathing.
If I’m going to cover it, I might as well use drywall. Would it be acceptable to put a sheet of drywall over all these studs (actually part of a truss), leaving a 1.5 inch gap between the drywall and the insulation, and leaving a ~1.5 inch gap at the bottom? Or should I cut pieces of drywall to fit between each of the stud “bays” and be in contact with the foam?
I’m going to blow in more insulation in the attic, so I figure I should address anything now that might need to be fixed, rather than have to disturb the insulation later.
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