## 3 Results
In the case where EPS is used as the insulation material and electricity, natural gas, and coal are used as the fuels, the optimum insulation thicknesses and annual financial gains for five different wall types are presented in Figure 4.  
According to Figure 4, the smallest insulation thickness was obtained when coal was used as the fuel. This value was 0.0017 m for a 19 cm perforated brick, while it decreased to 0 m for the Ytong wall type. The biggest value of the optimum insulation thickness was obtained when electricity was used as the fuel in other wall types except the Ytong wall. In case rock wool is used as the insulation material and electricity, natural gas, and coal are used as the fuels, optimum insulation thicknesses and annual financial gains for five different walls are given in Figure 5.  
Figure 4: Interval plot of (**a**) optimum insulation thickness values (m) and (**b**) annual financial gains (USD/m\({}^{2}\)) with EPS insulation material for Hatay. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multicolumn{4}{c}{**Insulation Material: XPS**} & \multicolumn{4}{c}{**Insulation Material: EPS**} & \multicolumn{4}{c}{**Insulation Material: RW**} \\ \hline
**Wall** & **Fuel** & **Optimum** & **Financial** & **Wall** & **Fuel** & **Optimum** & **Financial** & **Wall** & **Fuel** & **Optimum** & **Financial** \\
**Type 1** & **Type 2** & **Thickness** & **Gain** & **Type 1** & **Type 2** & **Thickness** & **Gain** & **Type 1** & **Type 2** & **Thickness** & **Gain** \\ \hline
1 & 1 & 0.0069 & 1.11 & 1 & 1 & 0.0118 & 1.45 & 1 & 1 & 0.0051 & 0.85 \\
2 & 1 & 0.0000 & 0.00 & 2 & 1 & 0.0017 & 0.10 & 2 & 1 & 0.0000 & 0.00 \\
3 & 1 & 0.0011 & 0.11 & 3 & 1 & 0.0058 & 0.45 & 3 & 1 & 0.0000 & 0.00 \\
4 & 1 & 0.0059 & 0.85 & 4 & 1 & 0.0108 & 1.20 & 4 & 1 & 0.0039 & 0.59 \\
5 & 1 & 0.0000 & 0.00 & 5 & 1 & 0.0000 & 0.00 & 5 & 1 & 0.0000 & 0.00 \\
1 & 2 & 0.0024 & 6.97 & 1 & 2 & 0.0322 & 7.62 & 1 & 2 & 0.0202 & 6.46 \\
2 & 2 & 0.0126 & 1.96 & 2 & 2 & 0.0221 & 2.62 & 2 & 2 & 0.0091 & 1.46 \\
3 & 2 & 0.0166 & 3.25 & 3 & 2 & 0.0262 & 3.90 & 3 & 2 & 0.0136 & 2.74 \\
4 & 2 & 0.0214 & 6.03 & 4 & 2 & 0.0159 & 1.18 & 4 & 2 & 0.0190 & 5.52 \\
5 & 2 & 0.0000 & 0.00 & 5 & 2 & 0.0089 & 0.64 & 5 & 2 & 0.0000 & 0.00 \\
1 & 3 & 0.0227 & 7.11 & 1 & 3 & 0.0326 & 7.77 & 1 & 3 & 0.0205 & 6.60 \\
2 & 3 & 0.0129 & 2.02 & 2 & 3 & 0.0225 & 2.69 & 2 & 3 & 0.0094 & 1.52 \\
3 & 3 & 0.0169 & 3.33 & 3 & 3 & 0.0419 & 4.63 & 3 & 3 & 0.0139 & 2.82 \\
4 & 3 & 0.0217 & 6.16 & 4 & 3 & 0.0315 & 6.82 & 4 & 3 & 0.0193 & 5.65 \\
5 & 3 & 0.0001 & 0.01 & 5 & 3 & 0.0093 & 0.68 & 5 & 3 & 0.0000 & 0.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Optimum insulation thickness values (m) and annual financial gains (USD/m\({}^{2}\) year) with different insulation materials for Hatay. According to Figure 5, the smallest insulation thickness was obtained when coal was used as the fuel. When using perforated brick 19 cm, solid brick 22 cm, and Ytong 15 cm wall types, it is economically more advantageous not to use the insulation material. The reason for this is that the energy gain from insulation is lower than the insulation investment. In the case of using electricity as the fuel for a 15 cm concrete wall, the optimum insulation thickness is calculated as 0.0205 m. When examining the annual fuel savings, it is evident that using electricity as the fuel type results in higher savings compared to other fuel types. As a result of all calculations made for Hatay province, the optimum insulation thickness varies between 0.0000 m and 0.0118 m when coal is used as the fuel type, between 0.0000 m and 0.0419 m for electricity, and between 0.0000 m and 0.0322 m for natural gas. It can be seen that the lowest values were obtained when coal was used as the fuel. When each wall structure is evaluated individually, and the insulation material is varied among the five wall structures examined, the highest optimum insulation thickness is achieved with EPS, followed by XPS and rock wool, respectively. Altering the fuel type did not change this ranking.