The R-value of a stress-skin panel varies depending on the thickness and type of foam core used. According to a study by Oak Ridge National Laboratory, the "whole-wall" R-value of a wall with a 3-1/2" EPS core is 14 compared to 9.8 for a 2"x 4" wood framed wall insulated with R-11 fiberglass insulation. When the performance of the whole wall system is considered, stress-skin panels perform better than traditional systems because they are manufactured in a controlled environment characterized by uniform fabrication of components without gaps or air pockets.