Can polyiso made for roofing applications be used on walls?
Ry38men8ZA
| Posted in Green Building Techniques on
I cannot find any non-foil faced polyiso for an exterior retrofit in my local area. Several retailers have polyiso made for roofing application from Altas or Hunter such as Hunter Panels H-Shield. Can these be used for wall applications?
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Replies
The reason you will not generally find polyiso rigid insulation without foil facings is that it is too water absorptive and will outgas and lose its R-value unless faced with an impermeable membrane. Under a roofing membrane, it will perform OK, but not as well as wall insulation.
However, as wall insulation, foil-faced polyiso board is a near-perfect vapor barrier and one must be very careful about placing a vapor barrier in any wall system, particularly if there is another vapor barrier or vapor-impermeable material installed.