The passage of heat through clothing is a complex Process involving conduction, convection and radiation. It has long bean known that thermal transfer coefficient is the one of the factors governing the flow of heat through fabrics. In this study, model experiment has been carried out with a Warmth Retaining Tester of ASTM-D1518-64 type. Total thickness, number and combination method of air layers have been given as factors in experiment. Artificial air spacers for air layer were made of 3mm thick plywood and then they were put between 4 layers of fabrics for making proper clothing weather. The conclusions of this study are as follows; 1, Within 15mm of total thickness of air layer, total thickness is in direct proportion to Thermal Insulation Value (T.I.V.). 2, T.I.V. has greater influence upon total thickness of air layers than number of them. 3, T.I.V. is greatest when air layer is 3-6mm, on the contrary, T.I.V. does not have on effect when air layer is 9mm and over.