Aluminum foil that is 0.001" thick has a perm rating of 0.01 Aluminum foil that is 0.00035" thick has a perm rating of 0.05 0.0006 inch polyethylene has a perm rating of about 0.06 0.004 inch polyethylene has a perm rating of about 0.08 Conventional fiberglass insulation facing that is a ...