In clothing engineering, in the technical design of clothing, the influence of the type of embedded materials and the construction of clothing composites on the overall thermal properties of the clothing has been insufficiently researched, which is particularly important in the case of clothing for special services (army, police, mountain rescue serrvice, firefighters, etc...). The research of the mentioned influences was carried out on an integrated measuring system for comprehensive testing of thermal properties of clothing, installed in the Laboratory for Thermal insulation properties of clothing of the Department of clothing technology at the University of Zagreb Faculty of Textile Technology. The mentioned measuring system consists of a thermal manikin, a hot plate, a multipurpose differential conductometer and a device for measuring differential gradients. The mentioned devices were designed, constructed, realized, measured and patented at the Faculty of Textile Technology. Devices for testing air permeability and water vapor resistance were also used in the research. Tests were conducted on six embedded materials (three materials for the outer shell and three materials for the lining and/or thermal insert), the combination of which was used to produce 15 clothing composites and 15 clothing systems, which were divided into three groups. In each group, clothing composites and clothing systems have the same outer shell, but they differ in the number of layers of embedding materials and the order in which they are incorporated, and the model groups differ from each other in the type of material that makes up the outer shells. The aforementioned research has shown that the type of embedding materials and the construction of clothing composites have a significant impact on the collective thermal properties of clothing, and served as the basis for establishing new guidelines and methods for the technical design of clothing with precisely defined thermal properties, in contrast to the previous ones, which are usually based on experiential knowledge. The doctoral thesis was developed within the framework of the project Development and Thermal Properties of Clothing IP-2018-01-6363 (ThermIC), funded by the Croatian Science Foundation. The materials used and the production of the clothing systems were financed by Konfeks d.o.o. Zagreb factory.