ISO insulation is good as an insulator and has a great R- value however unless you can find alum faced material you may have a problem,,the facer sheets on the iso is fiberglass matt and it sheds,,also the iso material will shed off if you rub it,,bottom line is if you dont encapsulate the whole board you will be very uncomfortable,,the iso is a irratant to skin and the fiberglass gets in your skin,,if you ever used fiberglass on anything you know what happens ,,,,,you will scratch yourself to pieces,,,you may be warmer but you wont get any sleep,,,,just be careful with the stuff,,,and it aint cheap,,,1" material is about $10.00 a sheet,,not wanting to rain on the iso material but it would take several other considerations to be able to use it
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