Korwall Industries have been building sandwich panels since 1958. In those early days we used honeycomb for core and plywood for the skins. All the volume for such new products was in the mobile home and the recreational vehicle Industry and those were our only customers for many years. Much has changed in all that time as you know. Our energy efficiency is very important and keeping cost down also. Since 1973 we have been building and marketing whereever possible the Expanded Polystyrene Sandwich Panel. Also in 1973 a waferboard plant in Minnesota started making large sheets of material in the standard thicknesses. Sandwich construction came out of the aricraft industry in the late 30's. They took aluminum H/C and bonded very thin skins to that for a very strong, light weight, structure for wings, fuselage, bulkheads and floors. Their strength is in the H/C and not the skins. We reversed that idea and bonded our 3/8" waferboard skins to E.P.S for structural panesl 8' wide and 24' long with no seams.