The thermal properties of clothing products are influenced by external environmental parameters, such as temperature, humidity, air flow and parameters related to the user's body, which mainly include temperature and humidity. Depending on the type of raw material, its thickness and the material manufacturing technique, clothing products are characterised by certain insulating properties to protect the human body from external factors. A multilayer system made of different material groups can change the thermal insulating capacity significantly, which cannot be determined by the testing of individual layers used in the production. In order to determine the influence of weather conditions on thermal insulation and air permeability, tests were carried out for two types of sleeping bags (summer and autumn) produced by the same manufacturer, differing in insulation thickness. Simulations were carried out using SolidWorks and verified using a Newton thermal mannequin. During tests, both the temperature (range from -20 degrees C to 20 degrees C) and humidity values were changed (range 40-80% humidity). For sleeping bags, the effective thermal insulation decreases along with the increase of temperature and decrease of humidity. It can be observed, for the autumn sleeping bags, that for a temperature of 20 degrees C and humidity of 60%, the thermal insulation is 1.063 m(2)Greek ano teleiaKGreek ano teleiaW(-1), while for a temperature of -20 degrees C and humidity of 60% thermal insulation increases significantly and amounts to 1.111 m(2)Greek ano teleiaKGreek ano teleiaW(-1). A similar situation occurs for the effective thermal insulation of a summer sleeping bag (20 degrees C/60% thermal insulation is 0.794 m(2)Greek ano teleiaKGreek ano teleiaW(-1), while for -20 degrees C/60%-0.851 m(2)Greek ano teleiaKGreek ano teleiaW(-1). During the tests, the humidity and temperature between the layers of the clothing system were also controlled, in order to learn more about the influence of these parameters on the thermal insulation properties of the sleeping bags.
