Term: Insulated Sheathing

Non-structural insulating board products with varying R-values and a wide variation in vapor permeability and drainage characteristics. Materials include expanded polystyrene (EPS), extruded polystyrene (XPS), polyisocyanurate (most often foil-faced), rigid fiberglass, and mineral wool.

Source: Guide to Insulating Sheathing, IRC FAQ: Cladding Attachment Over Insulating Sheathing, RR-0604: Incorporating Insulating Sheathing into the Design of the Thermal and Moisture Management System of the Building Enclosure