In this study, cooling degree day (CDD) and life cycle cost (LCC) analyses are applied to refrigerated warehouses in Turkey to determine the optimum insulation thickness. The external wall of refrigerated warehouses is considered as a sandwich wall and the insulation material is taken to be expanded polystyrene. Also, the base temperatures are assumed to be -20 degrees C, -18 degrees C, -12 degrees C, 0 degrees C, and 6 degrees C, while coefficient of performance (COP) values are 1.2, 1.5, 1.8, 2.1, and 2.5. As a result: (1) the insulation thickness is directly proportional to the insulation cost; (2) insulation thickness is inversely proportional to the electricity cost; (3) the maximum annual energy saving is found for a COP of 1.2, and the minimum rate is determined for a COP value of 2.5; (4) the maximum and minimum energy savings are found for -20 degrees C and 6 degrees C, respectively; (5) the maximum total cost is found for COP=1.2; (6) CO2 emissions increase with increases in CDD for the unit surface area; and (7) an increase in COP values reduces CO2 emissions. C1 [Ozturk, Hande Mutlu] Pamukkale Univ, Dept Gastron & Culinary Art, TR-20160 Denizli, Turkey. [Dombayci, Omer Altan] Pamukkale Univ, Dept Mat Sci & Engn, Fac Technol, TR-20160 Denizli, Turkey. [Caliskan, Hakan] Usak Univ, Fac Engn, Dept Mech Engn, TR-64200 Usak, Turkey.