Theoretical model, experimental and real life tests done for estimate opportunity and gain from phase change material (PCM) application in glazing. Theoretical model and results of tests are described in the publication. Tested component was chosen according to widely used technologies and easily accessible materials. Double and triple glazed window with glazing thickness 6 mm was chosen. Pretested experiments show that pure paraffin could be used as PCM in glazing, however it has disadvantages. Annual real life test done in Temperate climate conditions. This publication explores of passive control of solar energy gain. Increasing the thermal capacity of glazing gaps leads to the decrease of thermal resistance. But if the thermal energy absorption and desorption is transformed from temperature changes to phase changes we receive specific thermal barrier with fixed defined point phase change. This barrier has its positive and negative effects. Detailed research was conducted and is described.