By using FOAMULAR® NGX™ XPS, the R-value of LP NovaCore sheathing increases as temperatures drop while other polyiso foam products can see a decrease in their R-value as temperatures drop. With LP NovaCore sheathing, builders in some climate zones can use 2x4 studs while still meeting strict energy codes. Plus – it can be used to meet energy codes anywhere a climate zone allows an R-value of 13+5, or 20+5.