## 8 Conclusions  
Integrating passive energy-saving measures in sports buildings offers a promising approach to enhancing energy efficiency while maintaining or improving occupant comfort. By prioritizing design improvements and material upgrades, sports facilities can achieve significant energy reductions and support broader sustainability goals. Future research should continue to explore innovative passive strategies and their impact on energy consumption, with an emphasis on practical applications and performance outcomes [6]. Incorporating passive measures into the design and renovation of sports buildings is essential for achieving a balance between energy efficiency and occupant comfort [71]. In Europe, approximately 1.5 million sports facilities have been constructed, many of which continue to operate at full capacity. This substantial number of facilities constitutes roughly 8% of the total building stock in certain countries and regions. These facilities are significant not only in terms of their number but also due to their impact on energy consumption. Sports facilities are responsible for approximately 10% of the overall global energy consumption, highlighting their importance in the context of energy efficiency improvements within the building sector. Additionally, sports facilities occupy a significant portion of built space, accounting for approximately 4% of the total built area in Europe. This considerable footprint underscores the critical role that these buildings play in regional and national energy strategies, particularly in efforts to enhance energy efficiency and reduce overall energy use [72; 73; 74]. In Serbia, while construction practices have improved recently, they have historically not focused on energy optimization. Today, energy optimization is a critical topic in professional discussions, particularly for residential buildings. Analysis of the entire building stock shows that nearly 50% of energy is consumed during building operations. This highlights the considerable economic and environmental importance of implementing measures to improve energy efficiency [75]. The implementation of targeted refurbishment measures aimed at enhancing the thermal performance of both transparent and opaque components of the thermal envelope can lead to significant reductions in energy consumption for space heating. In the context of this study, Scenario 1 (RQ1) involves the refurbishment of the building while excluding the main sports hall from the upgrades. Under this scenario, office comfort levels see an improvement of 15.8%. However, there is a noted decrease in the percentage of hours during which the office remains comfortable throughout the occupancy period. Despite this, Scenario 1 achieves a substantial 51.6% reduction in energy consumption for space heating. Scenario 2 (RQ2), on the other hand, focuses specifically on enhancing the thermal envelope of the main sports hall. This scenario results in a 20.7% decrease in heating energy consumption, alongside a notable increase in the proportion of hours with a positive comfort index, rising from 13.4% to 21.6% of the total occupancy period. This improvement is particularly significant given the varying comfort requirements of the different occupant groups within the sports hall--namely, spectators and players engaged in physically demanding activities. When the interventions outlined in Scenario 3, improvement of the whole sports facility, are implemented, it provides a 64.9% savings, and comfort conditions in the sports hall are slightly improved compared to Scenario 2, which raises questions about the economic justification of the investment. Notably, the findings suggest that implementing Scenario 1 alone yields comfort levels and energy savings comparable to Scenario 3. Therefore, Scenario 1 represents a more efficient strategy for improving the building's energy class, achieving significant energy savings while maintaining satisfactory comfort levels [59].