How to insulate unvented attic with foil faced rigid foam in 6 inch bays?
Im currently remodeling my house in southern california. Im interested in building an unvented attic since all my HVAC equipment and ductwork are in the attic. In addition, we’ve had rats and mice nesting in the fiberglass insulation before we tore it all out. This is a single story, 3200 sqft ranch house that will have quite a few vaulted ceilings. With that in mind, what is the best way to use foil faced rigid insulation to create an unvented attic?
Option 1: 5 inches of JM AP foil-faced polyiso screwed directly to the undersides of the rafters and foamed and taped to air seal
Option 2: 4 inches of Foamular in the bays glued to the plywood and 2 inches of JM AP screwed to the rafters
Option 3: 6 inches of Foamular in the bays, Radiant barrier attached to the rafters.
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