## 4 Results
### Evaluation of the Individual Retrofit Strategies  
#### 4.2.1 External Wall Retrofit Strategies  
Various external insulation strategies for the building's external walls were individually analyzed using DesignBuilder v.7 software. The study compared eight potential retrofit strategies suitable for implementation in Saudi Arabia. These strategies ranged  
Figure 4: Heat gains (**left**) and cooling electricity consumption (**right**) of the base case. Figure 5: Thermography of the base case facade (**left**) and window (**right**). from standard construction techniques, such as prefabricated wood and ETICS, to more dynamic approaches, like ventilated facades (Table 5). The ventilated facade strategy provides greater flexibility compared to standard methods, allowing for easier modifications and replacements of finishing layers. A variety of insulation materials available in the Saudi market were selected, along with different finishing layer options. Strategies such as prefabricated wood panels and ventilated facades with ACP (Aluminum Composite Panel) cladding offer low U-values of 0.153 W/m\({}^{2}\).K and 0.14 W/m\({}^{2}\).K, respectively, making them highly energy efficient. Another effective strategy is the ventilated facade with WPC (Wood Plastic Composite) cladding, known for its excellent heat retention capacity. However, the ventilated facade incorporating limestone, sandstone, or brick cladding, while offering aesthetic benefits, has a higher U-value of 0.24 W/m\({}^{2}\).K, making it less efficient in terms of thermal performance. The results revealed that all proposed retrofit strategies significantly reduced heat gains through the external walls, with reductions ranging from 50% to 75%, as shown in Figure 6. This reduction correlates with the decrease in U-values of the retrofitted walls. The ventilated facade with ACP cladding showed the most significant reduction, lowering heat gains by 75.4%, attributed to a U-value drop from 0.56 W/m\({}^{2}\).K in the base case to 0.15 W/m\({}^{2}\).K. The prefabricated wood panel strategy was closely followed with a 74.1% reduction. Other strategies, such as the ventilated facade with WPC or AAC brick cladding, also demonstrated considerable heat gain reductions. The ventilated facade with FC cladding was the least effective, offering a 47.16% reduction. In ventilated facade systems, the air gap creates a buffer zone that enables air circulation, assisting in heat dissipation and maintaining a lower temperature near the building envelope, which is advantageous during cooler months. The reduction in heat gains was directly reflected in the cooling energy demand, which, in the base case, amounted to 477,073.9 kWh. Table 5 presents the monthly cooling consumption for the various wall retrofitting strategies. The prefabricated wood strategy achieved the highest annual energy reduction at 18.04%, followed closely by the ventilated facade with ACP cladding (15.81%) and WPC cladding (15.37%). In contrast, the ventilated facade with FC cladding exhibited the lowest reduction at 11.06%. To determine whether the observed differences in cooling load were statistically significant, the Wilcoxon Signed-Rank Test was conducted using SPSS v.16 software, with a significance level of 0.05. This test was chosen as an alternative to the Paired-Samples \(t\)-test because the data did not follow a normal distribution for all strategies, as confirmed by the Shapiro-Wilk test. Table 5 shows that all the examined strategies led to a statistically significant reduction in cooling energy compared to the base case.