Dow STYROFOAM™ Brand Residential Sheathing is an extruded polystyrene board with plastic film facers on both sides to reduce job site damage to the insulation boards. In new construction and residing applications, it provides a level, even surface for the exterior sheathing and for new siding material. Plus, Dow STYROFOAM™ Brand Residential Sheathing helps enhance energy efficiency, reduce condensation and create an attractive, long-lasting home exterior.