The costs of fuels and energy in the Czech Republic have rapidly increased in the last two decades. This situation in the energy market has bolstered the interest in the development of heating and cooling systems utilizing renewable energy sources, especially solar energy. The utilization of renewable energy sources in residential and office buildings very often requires an effective way of thermal energy storage. Thermal energy storage is an essential part of most of the solar heating and cooling systems. The solar gains through the transparent part of the building envelope can reduce energy consumption for heating during the heating season thus saving the energy from conventional heat sources (electricity, natural gas, coal). On the other hand, solar heat gains through the building envelope contribute to overheating in summer or during the sunny days in spring and autumn. From this point of view the energy storage capacity of building structures plays an important role in indoor temperature control in a building. That means that building structures can be employed to store solar heat during the sunny and warm part of the day and release it at night when the outdoor temperature decreases. This approach is applicable only on sunny days with relatively high outdoor temperatures during the day and low outdoor temperatures at night. The sensible heat storage capacity of common building structures depends on the weight of the structure, its thermal capacity and the temperature difference between the start and the end of the heat storage process. Because of the thermal comfort requirements that limit the indoor temperature swing during the day the thermal capacity of common building materials is usually insufficient to provide thermal storage for this purpose. This is where latent heat thermal storage can be applied. Latent heat storage represents much more effective way to improve the thermal storage capacity of a building structure