With its closed-cell extruded polystyrene (XPS) construction, this board has high moisture resistance. An R-Value of 5.0 per inch of thickness makes it an excellent thermal insulator that increases the energy efficiency of your structures. And it retains its insulating properties over time. The board also provides an extra barrier against moisture infiltration. Choose between a square edge (CM) and an interlocking shiplap edge (SL) that helps reduce energy-robbing air leaks at seams and gaps.