## 4 Results
### Evaluation of the Individual Retrofit Strategies
#### 4.2.2 Windows Retrofit Strategies  
Achieving an effective facade retrofit in hot climates requires minimizing solar gains through windows as well. At the case study site, direct solar radiation lasts from 9:00 \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Strategy Code** & **Strategy Description** & **Unit Cost** [**SAR/m2**] & **Total Retrofit Cost** [**SAR**] & **Annual Cooling Cost Reduction** [**SAR**] & **Payback Period [**Year**]** \\ \hline S-WA-1 & VF with ACP cladding & 430 & 873,614 & 24,128 & 36.2 \\ \hline S-WA-2 & VF with FC cladding & 200 & 406,332 & 16,881 & 24.1 \\ \hline S-WA-3 & ETICS & 150 & 304,749 & 19,805 & 15.4 \\ \hline S-WA-4 & Prefabricated wood & 450 & 914,247 & 27,536 & 33.2 \\ \hline S-WA-5 & \begin{tabular}{c} VF with limestone \\ cladding \\ \end{tabular} & 380 & 772,031 & 17,133 & 45.1 \\ \hline S-WA-6 & \
\begin{tabular}{c} VF with sandstone \\ cladding \\ \end{tabular} & 430 & 873,614 & 17,147 & 51.0 \\ \hline S-WA-7 &
\begin{tabular}{c} VF with AAC brick \\ cladding \\ \end{tabular} & 240 & 487,598 & 20,935 & 23.3 \\ \hline S-WA-8 & VF with WPC cladding & 340 & 690,764 & 23,470 & 29.4 \\ \hline \hline \end{tabular}  
* AAC = Autoclaved Aerated Concrete, ACP = Aluminum Composite Panel, ETICS = External Thermal Insulation Composite Systems, FC = Fiber Cement Board, VF = ventilated Facade, WPC = Wood Plastic Composite.  
\end{table} 
Table 6: Initial cost and payback period of the different wall retrofit strategies. Figure 6: Percentage of the annual reduction in wall heat gains in the different external wall retrofit strategies (wall heat gains in the base case were 56,650 kWh). a.m. to 7:00 p.m. during the summer, peaking at 0.86 kW/m\({}^{2}\) at midday. To mitigate the resulting heat gains, replacing the glass panes of existing windows is an efficient method to reduce cooling demand. In this study, the base window consists of double 6 mm bronze glass with a 13 mm air gap, with a U-value of 2.66 W/m\({}^{2}\).K and a SHGC of 0.497. The study assessed the impact of various glazing retrofit strategies on the cooling load. These strategies included upgrading to triple glazing, applying low-e coatings, and incorporating smart electrochromic glazing. Additionally, the study explored enhancing insulation by filling the gaps between glazing panes with Argon gas. Table 7 summarizes the various strategies evaluated. Figure 7 illustrates the annual reduction in glazing heat gains achieved through various window retrofit strategies. The results indicate that the combination of smart glass and Argon gas insulation achieved the highest reduction in heat gains, with a notable decrease of 45%. This significant reduction can be attributed to the strategy's low U-value and SHGC. The inclusion of Argon gas markedly enhanced performance, increasing heat gain reduction by 9% for the smart glass strategy. Following this, the smart glass without Argon gas and the low-e coating strategies demonstrated reductions of 36% and 33%, respectively. In contrast, filling the base case window with Argon gas had a minimal impact, resulting in only a 2.72% reduction in heat gains. This difference is directly reflected in the observed annual cooling electricity consumption, as shown in Table 7. The most effective window retrofitting strategy overall was the smart window option, regardless of whether it was insulated with Argon gas, leading to reductions of 7.1% and 7.9% in cooling energy, respectively. The triple glazing and low-e coating strategies followed closely behind, while the effect of Argon gas in the base case window was negligible. Generally, the results suggest that the reduction in air conditioning energy consumption due to window retrofit strategies was statistically significant in most cases. However, the double glazing with Argon gas (S-W-4) exhibited a very low reduction; nonetheless, it is considered statistically significant due to its standard deviation being very close to that of the base case.