One of the largest energy consumers for many countries over the world is the housing and communal sector, so energy saving and the use of renewable energy in this sector make it possible to achieve significant energy savings. The realization of the energy saving potential is complicated by the great diversity of the existing housing stock, which requires an individual approach in solving the problems of energy saving and energy supply of buildings. The experience of Sweden, Finland, Germany and the USA in the use of passive solar heating systems is useful for Ukraine. These systems, when properly designed, have an efficiency of up to 60% and cover more than 50% of the heating load. However, the insufficient number of publications on the efficiency and implementation of passive solar heating systems for the climatic conditions of Ukraine caused the need to simulate the thermal mode of the building with such system to determine the possibility of energy needs covering. A building model has been created using the MatLab/Simulink software. This model allows determining temperatures of enclosure structures and indoor air in connection with variable environmental parameters, such as solar radiation, ambient air and soil temperatures. The solar irradiation to the building's exterior enclosure structures was calculated for each hour of the day during the year for Kherson's climatic conditions. Based on the simulation results, the indoor air temperature oscillations amplitudes, time displacement in heat input to the building, energy needs and duration of heating and cooling periods are determined. The thermal modes of the three residential building variants are compared: without a passive solar heating system, with the Trombe wall and the Trombe wall and shading shutters. It has been determined that using of the Trombe wall reduces heating energy need of 76.9%, but leads to a significant room overheating during the warm period of the year and, consequently, to increasing of cooling energy need by 3.4 times. It is shown that using of the Trombe wall with shading shutters leads to reducing the energy demand for both heating and cooling. Keywords: Trombe wall, energy need, heating, cooling, enclosure structures.