## 3 Results and Discussion
### Solar Radiation and Energy Requirements  
The variation of incoming solar radiation on vertical surfaces according to the months is presented in Figure 5 for all directions. It is seen that the solar irradiance originating from the west and east orientations are maximum during months with high air temperature, such as May, June, and July, while the solar radiation coming from the south direction is at the top during months with relatively low air temperatures, including September, October, November, December, January, February, and March. Moreover, it is found that the solar radiation coming from the southeast and southwest directions are higher compared to other directions during April and August, which are the months of seasonal transitions. When the solar radiation variation is analyzed based on the months, January and July are months exposed to minimum and maximum solar radiation with the levels of 45.7 W/m\({}^{2}\) and 132.4 W/m\({}^{2}\), respectively. These differences in incoming solar radiation values are not solely dependent on the air temperature. Incoming solar radiation on vertical surfaces is equal to the sum of the direct, diffuse, and reflected solar radiations. Direct solar radiation is related to the inclination angle of the surface and the zenith angle. Diffuse solar radiation  
Figure 4: Yearly average heating and cooling degree days for various direction.  
Figure 3: Heating and cooling degree days for each month.  
is determined using the declination angle, relative sunshine duration, altitude angle and latitude angle. Lastly, reflected solar radiation is calculated using the value of reflectance of the ground and the inclination angle of the surface. Consequently, meteorological and geographical conditions of the area where the building is located affect the incoming solar radiation value on vertical surfaces.  
An examination of the annual average solar radiation according to directions reveals that the north-facing wall receives the minimum amount of radiation, with 52.1 W/m\({}^{2}\). In contrast, the walls oriented towards the south, southeast, and southwest receive the highest solar radiation exposure, with values of 111.8 W/m\({}^{2}\), 111.6 W/m\({}^{2}\), and 111.6 W/m\({}^{2}\), respectively. These results indicate that the quantity of solar radiation incident at the surface can vary by over two-fold, based on the wall's orientation, as seen in Figure 6.  
Heating and cooling energy requirements are determined considering the solar radiation impact for various wall orientations, as shown in Figure 7. When the average  
Figure 5: Incoming solar radiation on vertical surfaces for each month.  
Figure 6: Incoming annual average solar radiation on vertical surfaces for various directions.  
heating energy requirements are calculated (by summing the heating energy requirements for each direction and dividing by the number of directions), the average heating energy is determined to be 56.8 MJ/m\({}^{2}\). Similarly, the average cooling energy requirement is calculated as 11.4 MJ/m\({}^{2}\). It is clearly seen that the average heating energy requirement is approximately five times higher than the average cooling energy requirement. The heating energy requirement variation graph shows that the north and south directions have the highest and lowest energy demands with values of 58.3 MJ/m\({}^{2}\) and 54.8 MJ/m\({}^{2}\), respectively. On the contrary, the south and north directions have the highest and lowest cooling energy requirements with values of 12.1 MJ/m\({}^{2}\) and 10.9 MJ/m\({}^{2}\), respectively.