Kingspan GreenGuard Plygood Ultra is an extra strong extruded polystyrene (XPS) sheathing that makes homes more energy efficient. It offers superior insulation with four times the R-Value of 7/16" OSB. With low moisture absorption and a perm rating greater than 1, it won't swell or warp and is not subject to moisture-related damage and deterioration. A reinforcing scrim facer makes Plygood Ultra extra durable. Yet it's lightweight and easy to install with staples, roofing nails, or plastic cap nails.