The importance of school buildings is considerable due to their function, character, purpose, and architectural design, and their refurbishment could lead to significantly better building energy performance. The current research was carried out on select school buildings and is based on a parametric study of the application of energy refurbishment of the thermal envelope (ERTE) and of select passive design systems (PD). The research analyzes the relevant parameters of planning and designing a Trombe wall system (TW), double skin facades (DSF), a green roof (GR), and shading – blinds (BL). In order to determine any possible benefits for increased energy-efficient heating and cooling, models of school buildings were designed using the EnergyPlus software. Climate data which represent a typical meteorological year for the city of Niš were used in the simulation. During modeling, the architectural features of the building were adhered to, as was the layout, the purpose, and the means of using the indoor space. The simulation results indicate that the individual application of the TW, DSF, and GR on the school building models leads to increased energy-efficient heating with decreased energy-efficient cooling. In contrast, the application of BL, independently or in combination with other PD systems, results in the significant increase in energy-efficient cooling. Adequate application of ERTE in combination with TW, DSF, and GR leads to increased energy-efficient heating, while application of ERTE in combination with BL and PD systems leads to the significant increase in energy-efficient cooling. Measures for increased energy-efficient heating and cooling include applying the TW+GR or the DSF+GR system, combined with BL, which confirms that combining numerous PD systems can contribute to significant energy efficiency improvements for the school building models. The application of proper thermal mass and glazing systems significantly increases energy - efficient heating. The application of a TW system, whose thermal mass is either a masonry wall or a 0,25m thick concrete wall, as well as the use of single glazing instead of triple glazing significantly increases energy-efficient heating. The application of a DSF system with an intermediate cavity 0,3 m wide and triple glazing leads to significantly increased energy-efficient heating, compared to applying a DSF system with an intermediate cavity 0.4 m or 0,5 m wide and single glazing. The results confirm that the application of a shading system significantly contributes to increased energy-efficient cooling for the building models. Application of a ventilated TW compared to a non-ventilated one, as well as of a ventilated DSF compared to a non-ventilated one, leads to a significant increase in energy-efficient cooling for the building models. The simulation results offer insight into which parameters provide significant energy efficiency for heating and cooling buildings and confirm the benefits of applying ERTE measures and select PD systems. The applied methodology could be modified, improved, and used in regions with similar climatic characteristics, which would provide a new approach to a decision-making process curbed by limited resources.