This study aims to find out the optimized insulation thickness of refrigerated warehouse with different envelope structures (RC and PC wall) and insulation materials (urethane and icynene). Each of them is compared according to the thickness of insulation (100, 150, 200 mm/50 or 250 mm) and the temperature of cold storage room (0, -6, -15$^{circ}C$). As results, it is proved to have the best economical efficiency in life cycle cost when PC wall with thickness of 100 mm (0 and -6$^{circ}C$) and 150 m (-15$^{circ}C$) urethane, respectively, are applied.