I have access to several 4'x 8' sheets of Johns Manville AP Foil Faced Foam Sheathing. It is 3" thick.http://www.jm.com/insulation/building_insulation/products/bid0022_ap_foil-faced.pdf
I thought if it is similar to OC 700 series I could strip off the foil and straddle 2' x 8' pieces of it across corners. Could add fiberglass behind it too if helpful. Anyone know,or can tell from the link, if it is useful.
Don