## 4 Discussion  
### Buildings' Thermal Loads  
According to the existing literature, the energy demand for heating and cooling in buildings can vary depending on the climatic characteristics of the location, as well as the construction typology and boundary conditions. Regarding the city of Athens, the specific heating energy demand of the two examined buildings was equal to 23.67 kWh/m\({}^{2}\) for B1 and 16.59 kWh/m\({}^{2}\) for B2, while the specific cooling energy demand was calculated at 31.83 kWh/m\({}^{2}\) for B1 and 14.34 kWh/m\({}^{2}\) for B2. These results are corroborated by multiple studies that investigate the thermal performance of residencies for the Athenian climatic conditions. Initially, in a study concerning a flat roof single-family house and the implementation of various retrofit techniques, the specific energy demand for heating was found to range between 18.09 kWh/m\({}^{2}\) and 31.02 kWh/m\({}^{2}\), while for cooling, it was between 31.65 kWh/m\({}^{2}\) and 37.21 kWh/m\({}^{2}\)[37]. Similarly, a study that examined a two-story residential building of 75 m\({}^{2}\) per story calculated the specific heating energy demand in the range of 21.64 kWh/m\({}^{2}\) and 26.95 kWh/m\({}^{2}\), and the specific cooling energy demand in the range of 24.69 kWh/m\({}^{2}\) and 38.83 kWh/m\({}^{2}\)[38]. Additionally, for a holistically retrofitted energy-positive four-story multi-family building in Athens, the specific heating/cooling energy demands were calculated at 10.7 kWh/m\({}^{2}\) and 24.4 kWh/m\({}^{2}\), respectively [11].  
Furthermore, for the Spanish city of Barcelona, the calculated annual specific heating energy demand was found at 25.93 kWh/m\({}^{2}\) for B1 and 21.63 kWh/m\({}^{2}\) for B2, and the specific cooling energy demand at 22.19 kWh/m\({}^{2}\) for B1 and 6.04 kWh/m\({}^{2}\) for B2. For the Mediterranean Spanish cities, according to the study of [PERSON] et al. [39], the annual specific heating demand for a mid-rise multifamily building varies between 27.8 kWh/m\({}^{2}\) and 68.4 kWh/m\({}^{2}\) and the specific cooling energy demand between 1.0 kWh/m\({}^{2}\) and 5.6 kWh/m\({}^{2}\). Additionally, for a three-story university building with a total floor area of around 4000 m\({}^{2}\) in the same climatic category as Barcelona, renovated according to the national guidelines of Spain, the specific heating energy demand was around 47 kWh/m\({}^{2}\) and the specific cooling energy demand was around 18 kWh/m\({}^{2}\)[40]. For the city of Munich, the calculations of the present analysis indicated a specific energy demand for heating at 35.57 kWh/m\({}^{2}\) for B1 building and 30.73 kWh/m\({}^{2}\) for B2, while the cooling demand was found to be 6.5 kWh/m\({}^{2}\) for B1 and 0.64 kWh/m\({}^{2}\) for B2. According to the literature, in a two-story single-family house in Munich, the yearly specific heating energy demand was calculated at around 28.0 kWh/m\({}^{2}\), while the specific cooling energy demand was at 1.5 kWh/m\({}^{2}\)[41]. [PERSON] et al. [42] examined the energy performance of typical buildings in the city of Munich for various energy standards. According to their calculations, the yearly specific heating energy demand varies between 12.7 kWh/m\({}^{2}\) for the Passive House standard and 54.5 kWh/m\({}^{2}\) for the KfW 85 national energy efficiency standard of Germany. For the Swedish city of Stockholm, the yearly energy demand for space heating was calculated at 37.88 kWh/m\({}^{2}\) for B1 and 32.65 kWh/m\({}^{2}\) for B2, while the cooling demand was found to be negligible. According to the national technical guidelines of Sweden, the newly constructed residential buildings should not overcome the maximum energy demand for heating at 40 kWh/m\({}^{2}\)[43] and a total energy performance of 55 kWh/m\({}^{2}\)[44]. Considering that the examined building was a well-designed one, the slightly lower specific heating demand is reasonable.