GreenGuard extruded polystyrene (XPS) does not absorb moisture and retains its insulating properties over time, making it an ideal exterior insulation. With an R-Value of 5.0 per inch of thickness, the board increases the energy efficiency of your structures. Plus, it's light weight, easy to handle, and easy to cut with a knife. GreenGuard Type VI 40 psi Insulation Board is designed for use in high load applications.