In the article, the authors presented the basic design issues connected with application of the Active Thermal Insulation (ATI), that combines in one system reduction of heat losses and efficient use of renewable energy. Due to delivery of free or almost free energy from a low-temperature medium, thermal barrier may be created within external envelope of heated building. The authors try to answer the question how to refine the system and adjust it to the local climate conditions. For this purpose, simulations are being carried out regarding the required position of the ATI in the wall, proper selection of the type and thickness of the material layers and ATI thermal effectiveness. The higher is the temperature of the medium supplied to active insulation, the greater are the savings of the energy lost from the building space, but also the amount of energy dissipated to the external environment is increased. If renewable energy source is of limited capacity, the savings may be smaller. So the structure of the building component containing ATI and the method of selection and distribution of insulation layers must take into account energy availability as well as the type and size of the heat storage. In the case of unlimited low grade energy source the optimal location of the ATI layer should be carefully determined.