## 4 Results
### Evaluation of the Combined Retrofit Strategies  
This section of the study assessed various combined retrofit strategies to examine their impact on cooling energy reduction while considering cost efficiency. A total of nine external wall retrofit strategies were combined with seven window retrofit strategies and four shading device strategies, resulting in an optimization process involving 224 different facade compositions. The combinations offering the best solutions form the \"Pareto front\", which is plotted along the bottom-left side of the graph (Figure 9). The optimal solutions identified prioritize both cooling energy reduction and cost efficiency, with the payback period serving as the main driver for optimization decisions. The following optimal solutions were identified:  
* S1: ETCIS, double-glazed windows insulated with Argon and louvers;
* S2: ETCIS, low-e coating windows, and louvers shading devices;
* S3: ETCIS, low-e coating with Argon insulation in windows and louvers.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Strategy Code** & **Strategy Description** & **Unit Cost** & **Total Retrofit Cost** & **Annual Cooling Cost Reduction [SAR]** & **Payback Period [Year]** \\ \hline S-S-1 & Smart Electric Blinds & 800 & 79,200 & 7484 & 10.6 \\ \hline S-S-2 & Window Louver & 300 & 29,700 & 6458 & 4.6 \\ \hline S-S-3 & Overhang-Wood & 400 & 39,600 & 5302 & 7.5 \\ \hline S-S-4 & Overhang-Metal & 750 & 74,250 & 5302 & 14.0 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Initial cost and payback period in the different shading devices retrofit strategies.  
Figure 8: Percentage of the annual reduction in glazing heat gains in the different shading devices retrofit strategies (glazing heat gains in the base case were 30,118 kWh).  
In all three strategies, ETICS is applied as external wall insulation, and louvers are used as shading devices. Therefore, the key differentiator in the comparison lies in the window retrofit approach. Strategy S3 demonstrated the highest reduction in heat gains through glazing, achieving a 50% reduction due to the combination of low-e coating and Argon gas insulation. In contrast, Strategy S1 provided the least reduction in glazing heat gains at 21.9%. These reductions in heat gains translated into annual cooling electricity savings, as shown in Table 11. Strategy S3 achieved the greatest reduction in cooling energy, with a 16% decrease compared to the base case, followed closely by Strategy S2 at 15.4% and Strategy S1 at 14.0%.  
It is important to note that the majority of the observed cooling load reduction, approximately 13%, can be attributed to the consistent use of ETICS for external wall insulation across all three strategies. This highlights the greater impact of external wall retrofits compared to window retrofits in reducing cooling electricity consumption. In terms of cost efficiency, as shown in Table 12, the three strategies demonstrated similar performance. However, Strategy S3 emerged as the most economically viable, with the shortest pay  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Strategy Code** & **Strategy Description** & **Cooling Energy [kWh]** & **Reduction [\%]** & **Sig. Value** \\ \hline S1 & ETCIS, louvers, Argon & 410,294 & 14.0 & 0.002 * \\ \hline S2 & ETCIS, louvers, low-e coating & 403,422 & 15.4 & 0.002 * \\ \hline S3 & ETCIS, louvers, low-e coating, Argon & 400,832 & 16.0 & 0.002 * \\ \hline \hline \end{tabular}
* Observed reduction is statistically significant at \(\alpha\leq 0.05\).  
\end{table}
Table 11: The annual cooling energy reduction in the examined combined retrofit strategies (compared to 477,074 kWh cooling energy in the base case).  
Figure 9: Optimization analysis results, where red points represent the optimal scenarios.