## 1 Introduction  
The rapid depletion of fossil fuels and its link to global warming and climate change poses a significant challenge to humanity, affecting several environmental, social, and economic aspects [1]. Projections suggest that global temperatures could rise by 1.5 \({}^{\circ}\)C by 2050 and by 2-4 \({}^{\circ}\)C by [2]. This temperature increase is expected to trigger a range of serious, interconnected consequences, including rising sea levels, altered rainfall patterns, and more frequent floods. The building sector plays a pivotal role in this issue, as it is the largest consumer of energy globally. It is estimated that buildings account for 36% of the world's energy consumption and contribute 40% of global carbon emissions [3]. The housing sector, in particular, is a major contributor, with residential buildings responsible for approximately 25% of global energy consumption [4]. There is a critical link between urbanization, global warming, climate change, and the need for building adaptation through retrofitting [5]. In this context, green investments can enhance energy efficiency across buildings, transportation, and other sectors in urban environments [6]. The rapid pace of urbanization exacerbates the strain on global resources and ecosystems, increasing the contribution of buildings to greenhouse gas emissions, which in turn accelerates global warming and climate change. As a result, buildings must be designed with a high degree of adaptability, allowing for the periodic retrofitting of construction elements and control systems. Designing for adaptability reduces the demand for unnecessary new construction and minimizes the waste and emissions associated with it. This can be achieved through strategies such as modularity, convertibility, flexibility, and upgradability [7]. Given that more than 70% of existing buildings are expected to still be in use by 2050, retrofitting is crucial for addressing environmental challenges. Retrofitting can reduce carbon emissions by 50-75% compared to new construction, especially when considering embodied carbon. Therefore, significant progress toward climate goals can be made by extending the life of existing buildings. Achieving this requires the adoption of high-performance standards, the provision of financial incentives, and the promotion of pilot projects [8]. Saudi Arabia faces the challenge of increasing energy consumption due to its hot climate, which has led to a high demand for cooling in buildings. Summer temperatures in most regions range from 35 \({}^{\circ}\)C to 45 \({}^{\circ}\)C [9]. As a result, the country has one of the highest energy consumption rates globally, with per capita emissions nearly four times the world average [10]. The average annual Energy Usage Intensity (EUI) for Saudi residential buildings is 249.5 kWh/m\({}^{2}\) for cooled spaces, resulting in an average annual Energy Cost Index (ECI) of 70.3 SAR/m\({}^{2}\) (18.75 USD/m\({}^{2}\)). The total annual energy cost for all households is estimated to be USD 1.41 billion [11]. While constructing new energy-efficient buildings that comply with green building codes is part of the solution, retrofitting existing buildings has become essential to enhance energy efficiency and improve the thermal performance of the building stock. Building retrofits are particularly crucial in Saudi Arabia, where approximately 70% of residential buildings lack thermal insulation despite the country's hot climate [12]. This emphasizes the need for retrofitting interventions to implement energy conservation and management strategies in the Saudi construction sector, where energy retrofitting of residential buildings presents a practical solution [13]. This aligns with Saudi Vision 2030, which seeks to enhance the country's environmental and economic sustainability [14]. Therefore, this study aims to propose and evaluate various individual and combined facade retrofit strategies that can reduce cooling demand in residential buildings located in hot climates while considering the investment costs.