This walki-in freezer was REGULARLY USED. The freezer insulation is 4" thick polyurethane, with an R-value of 31 and a k-factor of .118 - UL listed flame spread25; smoke developed 200 Walk-in cooler for product shelf life, Cooler insulation is 4" thick polystyrene, with an R-value of 17 and a k-factor of .24 - UL listed flame spread 15; smoke developed 15-125.