## 2 An Overview of the Impacts of Green Roofs  
Private benefits of green roofs are categorized as buildings' increased aesthetic value, improved sound insulation, extended membrane longevity, and reduced consumption of energy. Further, they enable LEED certification bonuses [26], along with bringing psychological and health benefits. In addition to the individual level, green roof installations also affect the public (environmental and social benefits). Constructing a green roof can lead to a decrease in energy needed for cooling and heating, which may vary depending on the analyzed climate zone, green roof type, and building envelope. In [27], results are categorized according to their location, where maximum energy savings are obtained in intensive green roofs comparison to black roofs, especially over non-insulated roofs, reaching to 84% energy savings in the cooling season and 48% in the heating season. Similar comparison (white, black, and green roofs) is analyzed in but these types of roofs are not widely spread in the location of the presented analysis. In this paper, the impact of green roofs is investigated in Belgrade, where the climate is considered to be Cfa according to and to Koppen-Geiger climate classification system [28]. It should be emphasized that the presented data from the literature mainly reflect energy savings only for the floor under the green roof, which is also taken into account in the economic analysis in the presented paper. Ref. [29] found that the installation of a rooftop garden in a building in Singapore could result in a saving of up to 15% in the annual energy consumption. Total energy savings in the range of 24 to 35% were the result of investigation performed in hot-humid climate areas [30]. The comparison presented in [31] ranks green roof performance above the traditional roof with an insulation layer (5-14% energy saving) in the experimental analysis performed during the cooling season in Spain. A specific study in cold and hot climate zones [32] concluded that application of green roofs leads to an annual reduction in heating load by 36.5% to 55% and an annual reduction in cooling load by 27.7% to 35.8%. Based on a comprehensive literature review related to this topic, ref. [6] concluded that the maximum energy savings of greenery systems are found during summer. In contrast, for winter conditions, the results can vary and are dependent on the conditions in which the research was conducted. The high absorption of solar radiation in urban areas may cause heat island effects. As a consequence, the temperature in the city center is significantly higher than in the surrounding rural areas [33]. This temperature difference is usually larger at night than during the day and this urban heat island (UHI) effect indirectly increases building cooling demand [34]. Still, the effects of UHI have been recognized since the 19 th century [35], and today, how their negative impacts are reflected in the social, economic, and environmental aspects is especially considered. Compared to standard flat roofs, this effect could be mitigated due to the reduction in heat flux in the green roof structure. Consequently, for buildings that are not heavily insulated, the reduction in the peak indoor temperature can reach 7 \({}^{\circ}\)C [36] during the cooling season. [PERSON] [26] presented the results of the simulations indicating that the green roof concept in Toronto and New York can reduce the average temperature of the roof by 1-2 \({}^{\circ}\)C. In addition, in ref. [37], it is calculated that in Venice, the temperature could be 4 \({}^{\circ}\)C lower if the green permeable surface were used instead of existing roofs. The numerical model for Belgrade [38] showed that with a different type of green roof structure, the reduction in temperature varies from 0.5 to 1.5 \({}^{\circ}\)C and 0.5 to 1.8 \({}^{\circ}\)C for the roof and pedestrian level, respectively.