Johns Manville R-Panel® rigid roof insulation board offers R-Values of up to R-23.6, providing high thermal efficiency. R-Panel is manufactured with a closed-cell polyisocyanurate foam core bonded to fiberglass-reinforced facers and designed for use over metal, nailable and non-nailable roof decks with a variety of membrane systems. R-Panel meets the International Building Code requirements for a foamed plastic roof insulation.