The Role of Regional Codes in Mitigating Residential Sector Energy Demand Sensitivity to Climate Change Scenarios in Hot–Arid Regions

Abstract

Rising temperatures are intensifying residential cooling demands in hot–arid regions, with national building codes playing a pivotal role in mitigating these effects. This study evaluates the energy performance of two high-density residential buildings, Noor City in Cairo and Banan City in Riyadh, using DesignBuilder version 7.0.2.006 simulations for 2023, 2050, and 2080 under RCP 4.5 projections, followed by comparative and code-swapping analysis that assessed the role of envelope design parameters. All parameters were constant, except for those dictated by each country’s code. Results show that under future climate conditions, cooling loads in the uninsulated Noor City rise by 69% by 2080, compared to a 32% increase in Banan City. A code-swapping analysis confirmed the regulatory impact; applying the Saudi envelope to Noor City reduced annual energy use by over 40%, while using the Egyptian code in Banan City increased it by more than 50%. Solar exposure analysis further revealed that Noor City’s unshaded façades contribute to elevated thermal loads. Additionally, a 20.48 kWp rooftop photovoltaic system offsets 32:35% of annual energy consumption in both cases. While operational benefits are evident, no full life cycle cost (LCC) analysis was conducted; future studies should address economic feasibility to guide code adaptation in lower-income contexts.

1. Introduction

In recent decades, global climate change has emerged as a pressing challenge, particularly given its impact on the built environment. As temperatures continue to rise, cities worldwide are experiencing increased energy demand, predominantly driven by a need for cooling in residential and commercial buildings [1]. In regions characterized by extreme climates, such as the Middle East, this surge in energy demand is amplified due to prolonged and intense heatwaves. This issue is especially critical in high-density urban areas, where the urban heat island effect compounds the warming effects of climate change, further straining energy infrastructure and increasing operational costs [2] (see Figure 1).

Buildings account for a significant portion of global energy consumption and greenhouse gas emissions, contributing approximately 30% of global energy demand and nearly 40% of greenhouse gas emissions [4]. Within buildings, energy is primarily consumed for heating, cooling, lighting, and appliances, with HVAC systems dominating energy use. Cooling loads are expected to grow sharply as global temperatures rise, placing increasing pressure on energy systems, particularly in arid and semi-arid regions [5]. These challenges underscore the critical importance of addressing energy efficiency in the building sector as part of global sustainability efforts [6].

In Egypt and Saudi Arabia, the building sector represents a substantial share of national energy consumption. Residential buildings alone account for approximately 42% of total energy use in Egypt and nearly 50% in Saudi Arabia [7]. Cooling loads dominate these figures, contributing 60:70% of total energy use in residential buildings, particularly in Saudi Arabia due to its extreme climate. Despite this, building codes in both countries differ significantly in their focus and enforcement [8]. Saudi Arabia has adopted a proactive approach to energy efficiency, enforcing strict insulation standards and regulatory frameworks under national initiatives, such as Saudi Vision 2030 and the Saudi Energy Efficiency Center (SEEC) [8]. This approach is facilitated by the country’s high-income status, centralized governance, and robust institutional capacity, which together enable the implementation of mandatory building codes. In contrast, Egypt’s building regulations have historically prioritized addressing urgent housing needs over long-term energy performance, reflecting its lower-middle-income status and the high demand for affordable housing. The fragmented nature of Egypt’s policy landscape and limited fiscal resources have hindered the enforcement of advanced energy codes [9]. Although Egypt introduced initiatives like the Green Pyramids Rating System (GPRS) and the Green Buildings and Energy code, these remain voluntary and have seen limited uptake, underscoring the broader socio-economic and institutional barriers to mainstreaming sustainability in its construction sector [10].

These disparities are further complicated by the rapid urbanization and high-density residential developments in both Cairo and Riyadh [11]. As two of the most populous and urbanized cities in the Middle East, they exemplify the contrasting challenges posed by rising energy demands. In Cairo, the absence of robust energy efficiency standards leaves residential buildings vulnerable to inefficient cooling systems and increasing energy consumption as temperatures rise [12]. Meanwhile, Riyadh faces the dual challenge of managing extreme climatic conditions while balancing the need for energy-efficient housing with ambitious urban development plans [13]. These conditions present an urgent need to reassess and adopt building practices to mitigate the impact of climate change and rising energy demands in both cities.

1.1. Objective, Research Questions, and Significance

This study aims to investigate how climate change will impact the energy performance of residential buildings in Cairo, Egypt, and Riyadh, Saudi Arabia, and to determine the role of regional building codes and practices in moderating these effects. The focus is on two high-density residential developments by Talaat Moustafa Group: Noor City in Cairo [14] and Banan City in Riyadh [15]. Both cities are situated in arid or semi-arid regions with intense summer climates, but they exhibit notable differences in their building codes and energy efficiency regulations. By simulating current and future energy demands under Representative Concentration Pathway (RCP) 4.5 climate projections for 2050 and 2080, this research seeks to reveal how regulatory differences contribute to building resilience against warming trends. The core objectives of this research are threefold:

• To quantify and compare the energy consumption and cooling load increases in the Noor City and Banan City case studies under projected climate scenarios.
• To assess the extent to which the regional building codes and design standards in Egypt and Saudi Arabia influence these projected increases.
• To provide actionable insights and design recommendations for developers and policymakers aiming to enhance the energy resilience of residential buildings in the Middle East.

Based on these objectives, the study addresses the following research questions:

• How will climate change affect the energy consumption and cooling loads of residential buildings in Cairo and Riyadh by 2050 and 2080?
• To what extent do regulatory differences contribute to the projected increase in energy demand in Noor City buildings compared to Banan City buildings under future climate scenarios?
• What design and regulatory strategies could be implemented to reduce future energy demands and enhance building resilience in both regions?

By addressing these questions, this research fills a critical gap in the literature by developing a comprehensive framework that integrates building energy simulation with regional regulatory analysis, an approach that has received limited attention in existing studies. Although previous work has examined climate adaptation and energy performance in buildings, few studies have systematically compared how differing building codes affect energy resilience in high-density residential contexts in hot–arid regions. By focusing on Cairo and Riyadh, our study not only highlights the distinct climatic challenges and regulatory approaches of these cities but also provides a novel comparative analysis of the Noor City and Banan City case studies under future climate scenarios (2050 and 2080). This rigorous investigation offers new insights into the interplay between building design, local codes, and climate resilience and yields actionable recommendations for developers, policymakers, and urban planners seeking to enhance energy efficiency and mitigate cooling loads.

1.2. Research Scope

Although this study focuses on residential developments in Cairo and Riyadh, addressing the unique climatic challenges and regulatory frameworks of key Middle Eastern contexts, the findings are limited in their direct applicability to regions with different climate profiles, urban configurations, or regulatory environments. Simulations were based on morphed climate data under the RCP 4.5 scenario for 2050 and 2080, introducing uncertainties and not capturing the full range of potential conditions (e.g., RCP 2.6 and RCP 8.5). Moreover, the research scope was confined to new constructions and building-code-related design features, deliberately excluding retrofitting of aged buildings and multi-factor influences (such as the temporal decay of insulation performance, HVAC efficiency variations, and occupants’ energy conservation behavior). Additionally, the environmental benefits of thermal insulation materials were assessed solely in terms of energy consumption without conducting a full life cycle assessment (LCA). Future research is recommended to incorporate diverse regional case studies, multiple climate scenarios, and comprehensive LCAs to enhance generalizability and support the development of more balanced, region-specific building codes and energy efficiency strategies. Additionally, the simulations were conducted without modeling the influence of adjacent buildings or urban shading effects, which may affect cooling loads in high-density contexts. This was performed to isolate the impact of building envelope characteristics; however, future studies should incorporate urban form interactions to capture microclimatic influences more comprehensively. It is acknowledged that the occupancy schedules derived from ANSI/ASHRAE 62.1-2022 may not fully represent the cultural and social occupancy patterns typical of Egyptian and Saudi households. However, in the absence of standardized regional data, this choice ensures methodological consistency and allows for a controlled comparison focused on building code characteristics. Future research should prioritize developing localized occupancy profiles to further refine such assessments.

2. Literature Review

2.1. Energy Demand in Residential Buildings

Residential buildings are significant contributors to global energy consumption, particularly in regions with hot climates where cooling demands are high. In the Middle East, residential energy consumption is a primary component of total electricity demand, with air conditioning accounting for the largest share of energy use during peak summer months [16]. This dependency on cooling systems places considerable strain on electrical grids, elevates operational costs, and contributes to increased greenhouse gas emissions [17]. Consequently, understanding the patterns and drivers of energy demand in residential buildings is crucial for developing effective energy policies and designing resilient urban environments [18].

The factors influencing energy demand in residential buildings are multi-faceted and include building design characteristics, occupant behavior, and climate conditions [19].

Table 1. The primary factors affecting residential energy use [19].

Factor	Description
Building Envelope	Insulation, glazing type, and materials used in walls and roofs.
HVAC Efficiency	The efficiency of air conditioning units and other HVAC components.
Occupancy Patterns	Number of occupants, activity levels, and usage of indoor spaces.
Local Climate	Temperature, humidity, and solar radiation levels vary by season and region.
Building Codes	Regional regulations for energy efficiency, insulation, and sustainable practices.

below summarizes some of the primary factors affecting residential energy use, with a specific focus on cooling loads.

These factors become even more critical in urban centers with high-density residential buildings, where cumulative energy demands can overwhelm infrastructure during extreme weather conditions [20]. In response, many countries have implemented building codes aimed at enhancing energy efficiency, which are particularly relevant for regions like Saudi Arabia, where national energy policies are tightly integrated with urban planning initiatives. For instance, Saudi Vision 2030 and SEEC mandates emphasize stringent insulation and efficient cooling systems to mitigate rising energy demands [21].

However, despite these regulatory efforts, the effectiveness of energy efficiency standards often depends on enforcement and adaptation to local climatic needs [22]. In Egypt, building codes are generally less stringent for insulation and passive cooling measures, partly due to historical reliance on natural ventilation in residential spaces [23]. This regulatory contrast sets the stage for a comparative analysis of the Noor City and Banan City developments, illustrating how local building practices influence the long-term energy resilience of residential buildings under climate change scenarios [24].

2.2. Impact of Climate Change on Building Energy Performance

The ongoing effects of climate change are anticipated to significantly impact energy demands in buildings worldwide, with particularly severe consequences for regions experiencing extreme temperature increases [25]. Rising global temperatures lead to increased cooling requirements in residential and commercial buildings, which can place enormous pressure on energy infrastructure [23]. Studies have shown that in arid and semi-arid climates, such as those in the Middle East, cooling loads are projected to rise sharply in response to even moderate temperature increases, making climate resilience a critical consideration in building design and energy planning [26]. Climate projections under the Intergovernmental Panel on Climate Change’s (IPCC) Representative Concentration Pathways (RCPs), which represent different greenhouse gas concentration trajectories, indicate that rising global temperatures will have substantial effects on building energy performance, particularly by increasing cooling loads in hot climates. Under the RCP 4.5 scenario, a stabilization scenario where emissions peak and then decline, temperatures are expected to increase by approximately 1.5–3 °C by the mid-21st century [27].

Table 2. The anticipated effects of climate change [28].

Climate Variable	Projected Change (RCP 4.5)
Temperature	Increase of 1.5–3 °C by 2050
Humidity	Variable, with a possible increase in arid areas
Solar Radiation	Potential increases in solar gain levels
Extreme Heat Events	Increase in frequency and duration

illustrates the anticipated effects of climate change on building energy performance in high-temperature regions, focusing on residential cooling demands [28].

As temperatures rise, buildings in warm regions require more intensive cooling to maintain indoor comfort, leading to increased energy consumption and higher operational costs. In response, building codes in some countries, such as Saudi Arabia, have begun incorporating climate-responsive strategies like enhanced insulation and lower window-to-wall ratios [29]. Such measures help mitigate the impact of rising temperatures by reducing heat gains, ultimately stabilizing energy consumption in the face of climate change [30]. In contrast, in regions where energy efficiency codes are less enforced, buildings may become increasingly vulnerable to rising energy costs and grid instability as cooling needs intensify. This difference underscores the importance of robust regulatory frameworks in fostering climate resilience in the built environment [31].

2.3. Influence of Contemporary Building Codes on Energy Performance Under Future Climate Scenarios

Comparative research published over the last five years confirms that the specific clauses embedded in national building codes, particularly those governing opaque-element U-values, glazing solar-heat-gain coefficients (SHGC), and envelope airtightness, strongly mediate a dwelling’s sensitivity to warming trends. Allard et al. compared the latest Finnish, Norwegian, Swedish, and Russian codes and found that tightening wall/roof U-values from ≈0.45 to 0.18 W/K.m² and imposing explicit air-leakage caps (≤0.6–1.5 h⁻¹ at 50 Pa) lower annual space-conditioning energy by 15–30% in Nordic test buildings; they stress that countries relying only on primary-energy caps without prescriptive envelope thresholds achieve markedly smaller savings [32].

In hot–arid contexts, Elnabawi’s parametric analysis [19] of four Gulf Cooperation Council (GCC) codes demonstrated that adopting Abu Dhabi’s ESTIDAMA envelope package (walls 0.30 W/K.m²; roof 0.20 W/K.m²; windows 1.9 W/K.m², SHGC 0.23) curtails annual electricity and cooling loads in a Bahraini villa by 24% and 29%, respectively, while the Saudi SBC yields ~15% energy and 16% cooling relief; Bahraini and Kuwaiti prescriptions with looser glazing limits exhibit negligible benefit. These studies highlight glazing U-value/SHGC and roof insulation depth as the dominant levers for peak-summer demand reduction [19].

Emerging urban-scale modeling reinforces those conclusions under explicit climate change pathways. Using shared socio-economic pathway weather files for 2050, Deng et al. [33] showed that Geneva neighborhoods face a 95–173% surge in cooling demand, yet a code-compliant retrofit that tightens roof and wall U-values to 0.21 W/K.m² and upgrades windows to U = 1.1 W/K.m²/SHGC 0.19 offsets 18:22% of that increase, with combined envelope measures producing 41.7% heating and 18.6% cooling savings. Parallel simulations for Cairo and Riyadh reveal that mandatory insulation in Saudi Arabia constrains 2080 peak-cooling escalation to +32%, whereas Egypt’s non-insulated baseline accelerates to +69% [33].

2.4. Building Codes and Regulations in Saudi Arabia and Egypt

Building codes play a pivotal role in shaping the energy efficiency and climate resilience of residential structures [34]. These codes govern various aspects of building design, including insulation standards, glazing requirements, and HVAC efficiency, which directly influence a building’s energy performance and its capacity to withstand climatic shifts [35]. In the Middle East, where extreme heat intensifies energy demand, building codes have gained increasing attention as tools for mitigating the environmental impact of urban development [36].

Saudi Arabia has taken substantial strides toward integrating energy efficiency and sustainability within its building practices [31]. The Saudi Energy Efficiency Center (SEEC) and the objectives outlined under Saudi Vision 2030 have established a framework that promotes energy conservation through rigorous building codes. Among these regulations, mandatory insulation standards and limitations on window-to-wall ratios (WWRs) are particularly influential in reducing the thermal gains in residential buildings, thus moderating cooling loads during peak summer months [37].

The Saudi Building Code (SBC) specifies that new residential buildings incorporate thermal insulation for walls and roofs and use high-performance glazing. These measures are designed to minimize heat transfer, thereby reducing the load on HVAC systems [30]. Table 3 summarizes key aspects of Saudi Arabia’s building code and Egypt’s building code requirements relevant to energy performance. These requirements have contributed to a more climate-resilient built environment in Saudi Arabia, particularly as cities like Riyadh continue to expand under extreme temperatures. The compliance and enforcement of such codes create a regulatory environment that supports sustainable urban growth and energy efficiency [37].

In contrast, Egypt’s building codes for residential structures have historically placed less emphasis on energy efficiency, partly due to a milder climate and the widespread use of natural ventilation in traditional housing [10]. While recent policy discussions have called for stricter energy regulations, mandatory insulation requirements and other climate-responsive measures are still limited [38] (see Table 3). The building codes in Egypt provide general guidelines for thermal comfort but lack the enforceable standards seen in Saudi Arabia for insulation, WWRs, or HVAC efficiency. This regulatory gap has implications for the energy performance of residential buildings, particularly as Egypt’s urban areas, like Cairo, face growing demands for cooling [39].

Table 3. Energy performance requirement comparison between Saudi Arabia and Egypt [40,41].

Building Code	Areas	Properties of the Building Envelope
		U-Value (W/m2·K)					SHGC
		Walls	Roofs	Windows			Glazing
				Façade Area < 40%	Façade Area 40:50%	Façade Area > 50%
Saudi Arabia	Riyadh	0.454	0.272	2.89	2.38	1.87	0.25
Egypt	Cairo *	-	-	-	-	-	-

* Egypt’s building codes primarily offer general guidance on thermal comfort without strict mandates related to insulation and glazing.

Table 3. Energy performance requirement comparison between Saudi Arabia and Egypt [40,41].

Building Code	Areas	Properties of the Building Envelope
		U-Value (W/m2·K)					SHGC
		Walls	Roofs	Windows			Glazing
				Façade Area < 40%	Façade Area 40:50%	Façade Area > 50%
Saudi Arabia	Riyadh	0.454	0.272	2.89	2.38	1.87	0.25
Egypt	Cairo *	-	-	-	-	-	-

* Egypt’s building codes primarily offer general guidance on thermal comfort without strict mandates related to insulation and glazing.

3. Methodology

This study follows a structured approach to evaluate the energy performance of two high-density residential developments, Noor City in Cairo, Egypt, and Banan City in Riyadh, Saudi Arabia, under both current (2023) and future climate scenarios (2050 and 2080). The methodology integrates building energy modeling, climate projection, code-swapping simulations, and comparative economic analysis to assess how regional building codes influence energy demand and cooling loads, as illustrated in Figure 2. The research process began with the collection of detailed data for both case studies, encompassing architectural features, HVAC systems, and occupancy patterns, ensuring accurate input parameters for energy modeling. Regional building code requirements for Egypt and Saudi Arabia were analyzed to define key envelope characteristics, including insulation levels, window-to-wall ratios (WWRs), and glazing types. Subsequently, energy models for both buildings were developed using DesignBuilder version 7.0.2.006 which employs the EnergyPlus simulation engine. Baseline simulations were conducted for 2023 to establish current energy performance profiles. To account for future climatic impacts, weather files for 2050 and 2080 were generated using the “CCWeatherGen” tool under the IPCC RCP 4.5 scenario, incorporating temperature projections while maintaining consistency in other climatic variables. Critical operational parameters, such as HVAC setpoints, internal loads, and occupancy schedules, were standardized across both models to isolate the effects of building code differences. The occupancy patterns were based on the ANSI/ASHRAE 62.1-2022 multifamily residential diversity profile, selected to provide a harmonized comparison framework while controlling for cultural variability, aligning with the study’s objective of isolating code-driven effects. To further validate the influence of code-specific envelope provisions, a code-swapping analysis was conducted, wherein Saudi code requirements were applied to the Noor City model and Egyptian code specifications were applied to the Banan City model. This allowed for a controlled assessment of regulatory impacts independent of climatic and morphological variables. Finally, the comparative simulations were expanded to evaluate the economic implications of code adoption, quantifying operational cost differences and life cycle trade-offs. The outcomes of this comprehensive methodology informed actionable design recommendations and policy insights aimed at enhancing energy resilience in hot–arid regions.

3.1. Case Study Description

This study investigates two residential developments by the Talaat Moustafa Group: Noor City in Cairo and Banan City in Riyadh. Both projects are representative of high-density residential contexts in their respective regions. However, the effect of adjacent buildings was not directly modeled in the DesignBuilder simulations. This decision was made to isolate the impact of building envelope characteristics and regulatory frameworks on energy performance while maintaining controlled and comparable boundary conditions. Noor City reflects the Egyptian approach, with less emphasis on energy efficiency measures like insulation, while Banan City adheres to stringent Saudi codes mandating energy-saving practices. The common developer further ensures design consistency, enabling a focused analysis of how local building codes and environmental factors influence energy performance under current and future climate scenarios.

The projects were chosen due to their geographic and climatic contrasts, alongside their identical total floor areas, despite differences in vertical distribution. Noor City has more floors, while Banan City compensates with larger per-floor areas. This equivalence was essential to attribute differences in energy consumption and cooling loads to variations in building envelope characteristics, local regulations, and climate rather than size. Critical architectural parameters, including façade and roof areas, were normalized between the two developments. However, a divergence was noted in the window-to-wall ratio (WWR), as Saudi Arabian standards require a lower WWR to minimize solar heat gain, whereas Egyptian regulations permit a higher ratio. This distinction was explicitly integrated into simulation models. Data for these case studies were obtained directly from the developer and relevant national building codes and further corroborated with findings from the prior literature on similar projects, ensuring that the simulation results reflect realistic and validated operating conditions.

Noor City, located in Cairo’s New Administrative Capital, represents a typical high-density residential project in Egypt. The selected building (Type D) has a ground floor plus seven typical floors, as demonstrated in Figure 3. Due to Egypt’s relatively mild winter temperatures and lack of stringent building regulations, Noor City does not include additional insulation or passive cooling features. The building is heavily reliant on mechanical cooling through split AC systems, which could lead to increased energy demands under rising temperatures [14].

However, Banan City, situated in Riyadh, Saudi Arabia, is another multi-story residential development by Talaat Moustafa Group. Banan City’s R4 building comprises a ground floor and six typical floors, as demonstrated in Figure 4, which is designed to comply with Saudi Arabia’s stringent building codes, which mandate insulation and efficient glazing [15].

Table 4. Noor City and Banan City case studies’ characteristics [14,15].

Attribute	Noor City, Type D Characteristics (Egypt)	Banan City, R4 Building Characteristics (Saudi)
Location	Cairo, Egypt (latitude: 30.0′ N; longitude: 31.5′ E; elevation: 243 m)	Riyadh, Saudi Arabia (latitude: 24.7′ N; longitude: 46.7′ E; elevation: 620 m)
Building type	Multi-story residential building	Multi-story residential building
Floors	Ground floor + 7 typical floors (489.4 m2/floor = 3915.2 m2 total floor area)	Ground floor + 6 typical floors (557.4 m2 per floor = 3902 m2 total floor area)
Total units	28 apartments (4 apartments per floor)	24 apartments (4 apartments per floor)
WWR	17.60% (690 m2)	10.52% (349.9 m2)
Net external wall area	3238.1 m2	3149.1 m2
Unit sizes	Apartments range from approximately 60 to 152 m2, including bedrooms, bathrooms, reception areas, and kitchens	Apartments range from approximately 60 to 152 m2, including bedrooms, bathrooms, reception areas, and kitchens
Wall construction	20 mm plaster (exterior) + 150 mm hollow concrete block + 20 mm plaster (interior) U-value = 0.955	20 mm plaster (exterior) + 150 mm hollow concrete block with 50 mm polystyrene insulation + 20 mm plaster (interior) U-value = 0.353
Roof construction	25 mm roofing tiles + 25 mm mortar + 10 mm sand + 320 mm concrete slab + 13 mm cement plaster U-value = 0.256	25 mm roofing tiles + 25 mm mortar + 10 mm sand + 50 mm polystyrene insulation + 320 mm concrete slab + 13 mm cement plaster U-value = 0.183
Glazing	Single-glazed, clear frosted windows with aluminum frames	24 mm double-glazed (6 mm glass + 12 mm air gap + 6 mm glass), clear frosted windows with aluminum frames
Air infiltration	0.8 air changes per hour (ACH)	0.8 air changes per hour (ACH)
HVAC system	Split air conditioning units; Coefficient of Performance (COP): 4.0; cooling set points: 24 °C to 28 °C; no fresh air unit	Split air conditioning units; Coefficient of Performance (COP): 4.0; cooling set points: 24 °C to 28 °C; no fresh air unit
Lighting power	3.3 W/m2, using LED lighting	3.3 W/m2, using LED lighting
Equipment power density	5.0 W/m2 across all living areas	5.0 W/m2 across all living areas
Domestic hot water	Stand-alone electric water heater, 11.4 L/person/day, with a COP of 0.85	Stand-alone electric water heater, 11.4 L/person/day, with a COP of 0.85
Occupancy assumption	6 residents per apartment (2 adults, 4 children), aligned with typical Egyptian residential occupancy patterns	6 residents per apartment (2 adults, 4 children), aligned with typical Saudi residential occupancy patterns

summarizes the main characteristics of Banan City. Occupancy patterns were obtained from ANSI/ASHRAE Standard 62.1-2022 [42]. The use of ANSI/ASHRAE Standard 62.1-2022 occupancy schedules ensures a standardized basis for both case studies, thereby isolating the impact of building code parameters on energy performance, as per the methodological approach.

3.2. Simulation Tools and Data Sources

This study employs DesignBuilder, a widely used building energy modeling software, to simulate the energy performance of Noor City and Banan City under both current and future climate conditions. DesignBuilder, which uses the EnergyPlus engine, allows for precise input of building characteristics, HVAC specifications, and operational schedules, making it ideal for detailed energy analysis across diverse climates. For this study, models of both buildings were developed with DesignBuilder, incorporating structural details, HVAC systems, and occupancy patterns based on data collected for each case study, as shown in Figure 5. Monthly outputs for energy consumption and cooling loads were generated to enable a seasonal analysis of demand.

To assess the influence of architectural features on façade solar exposure, solar incident simulations were conducted for both Noor City and Banan City case studies. Figure 6 presents the annual solar irradiation maps, highlighting the effects of balconies, protrusions, and façade orientation on solar gain distribution. The simulation results reveal a marked difference in solar exposure patterns between the two buildings. In Banan City, the presence of deeper balconies and recessed façade elements significantly mitigates direct solar exposure on vertical surfaces. This is evident from the prevalence of green to yellow zones (350–700 kWh/m² annual exposure) on most façades, with only limited areas, such as lower corner zones, exhibiting higher exposure exceeding 1000 kWh/m². These architectural shading devices effectively reduce solar heat gain, contributing to improved thermal performance. Conversely, Noor City displays extensive areas of high solar exposure, with large façade sections receiving over 1000 kWh/m² annually, as indicated by the dominant orange and red color bands. The limited use of shading elements and higher window-to-wall ratio (WWR) exacerbate solar gains, particularly on south- and west-facing façades. This comparative analysis underscores the critical role of passive architectural features, such as balconies and façade articulations, in moderating solar heat gains. The findings align with the observed differences in cooling loads and support the argument for integrating shading strategies into Egypt’s building code provisions to enhance energy resilience.

To project future climate conditions for the years 2050 and 2080, the study utilized the “ccweathergen” tool to create weather files under the Representative Concentration Pathway (RCP) 4.5 scenario, which has been developed and validated for its results by researchers at Southampton University [43]. In RCP-4.5-based weather files, temperature changes are guaranteed, but other variables remain unchanged unless specifically modified based on climate projections. Specifically, the baseline input for ccweathergen was derived from climate data files obtained from the ASHRAE weather database incorporated within DesignBuilder [44], ensuring that all adjustments were made on a reliable and standardized dataset. This scenario, representing a stabilization pathway where global emissions peak and gradually decline, anticipates a temperature rise of approximately 1.5–3 °C by mid-century (see

Table 5. Key parameters changed in weather data files [43].

Parameter	Current Scenario	2050 Projection (RCP 4.5)	2080 Projection (RCP 4.5)
Average Temperature Increase	Baseline (DesignBuilder weather data)	+1.5 °C to +2 °C	+2.5 °C to +3 °C
Other Variables	Unchanged (based on current data)	Unchanged	Unchanged

). The adjusted weather files created using ccweathergen reflect these projected increases and were applied in DesignBuilder to simulate the energy impacts of climate change on both buildings.

The combination of DesignBuilder and ccweathergen provides a robust framework for evaluating how each building performs under evolving climate conditions. This approach allows for a consistent comparison of energy demands across current and projected scenarios, laying the foundation for an analysis of the buildings’ resilience and the role of regional building regulations in moderating future energy demands.

4. Results and Discussion

The results present a comparative analysis of the energy consumption and cooling loads of Noor City and Banan City under current and projected climate conditions for the years 2050 and 2080. By analyzing monthly data, this study evaluates the impact of regional building codes and climate resilience on each building’s energy demands, emphasizing how design and regulatory differences influence energy performance under climate change.

4.1. Current and Future Weather Data Analysis

The temperature projections for 2050 and 2080 shown in Figure 7 and Figure 8 are based on ccweathergen-morphed weather files, following the RCP 4.5 scenario as detailed in Jentsch et al. (2008) [43] while ensuring consistency with the simulation framework described in Section 3.2. The weather profiles of Cairo and Riyadh reveal distinct climatic conditions that significantly influence the energy performance of buildings in each city. In 2023, Cairo experiences winter temperatures ranging from 2.4 °C to 21 °C in January, with an average relative humidity of 68%. Summer highs reach up to 44 °C, while humidity remains moderately high (50–60%). Climate projections indicate a gradual warming trend; by 2050, January temperatures are expected to range between 5 °C and 22.6 °C, increasing further to 24.1 °C by 2080, with summer peaks approaching 50 °C. Relative humidity is projected to remain relatively stable (Figure 7). In contrast, Riyadh’s 2023 climate is characterized by a drier profile, with January temperatures ranging from 4.6 °C to 28 °C and an average humidity of 43%. Summer temperatures peak at 45.2 °C, while humidity drops below 11%. Future projections show Riyadh’s January temperatures rising to 7.1–30.2 °C by 2050 and reaching 31.4 °C by 2080, with summer highs also hitting 50 °C. Humidity levels during peak months are expected to remain consistently low, around 7–10% (Figure 8). These divergent climatic trends imply that Cairo’s higher humidity and gradual warming will result in prolonged but moderate cooling demands. Conversely, Riyadh’s extreme temperatures and low humidity are anticipated to amplify peak cooling loads. This climatic analysis provides a critical foundation for understanding how regional weather patterns and future climate projections directly impact residential energy consumption and cooling performance.

4.2. Validation of Simulation Models

The simulation results were validated by comparing the annual energy consumption figures derived from the DesignBuilder models with well-established reference levels reported in the literature. In this study, the Banan building exhibited an annual energy consumption of 100.59 kWh/m², while the Noor building demonstrated a value of 81.50 kWh/m². These outcomes are consistent with the performance benchmarks documented in previous studies. For instance, Aldossary et al. (2017) recommend energy performance reference levels for domestic buildings in Saudi Arabia within the range of 77–98 kWh/m²/year [45]. This benchmark supports the overall validity of the simulation outputs, affirming that the energy performance modeled for the Banan building is representative of high-density residential construction in Riyadh. Similarly, Umbark et al. (2020) reported that apartment-style buildings in Egypt typically consume around 69–79 kWh/m²/year, further reinforcing the credibility of the simulation results, particularly for the Noor building, which closely mirrors this typology [46] (see Figure 9). By aligning the simulation findings with these established reference values, the reliability of the modeling approach is substantiated. This validation confirms that the DesignBuilder simulations offer a robust framework for assessing the energy performance of residential buildings under both current and projected climate conditions.

4.3. Current Weather Data Scenario Comparison

Under current climate conditions, Noor City’s case study demonstrates lower energy consumption and cooling loads for much of the year, which can be attributed to both Cairo’s relatively milder climate and the building’s specific configuration. As illustrated in Figure 10, the absence of shading elements and higher exposure to direct solar radiation in Banan City contrasts with Noor City’s recessed façades and balconies, influencing thermal performance alongside climatic factors.

In January, Noor City registers minimal cooling loads at 2.72 Wh/m², while Banan City, reflecting Riyadh’s warmer winter baseline and solar exposure patterns, records a significantly higher value of 173.08 Wh/m². As seasonal temperatures rise into spring and early summer, both buildings experience increased cooling demands. By June, Noor City’s cooling load reaches 8219.91 Wh/m², while Banan City records 10,498.13 Wh/m². The insulating envelope in Banan City contributes to moderating this increase by reducing direct heat gains. During peak summer months, the vulnerability of uninsulated buildings becomes more evident. In July, Noor City’s cooling load slightly exceeds that of Banan City, at 11,338.51 Wh/m² compared to 11,293.39 Wh/m², despite Cairo’s less severe summer temperatures. This trend reflects the compounded impact of the lack of insulation and solar exposure on energy demand. By December, cooling loads in Noor City drop to 90.12 Wh/m², whereas Banan City maintains elevated demand at 274.63 Wh/m², consistent with Riyadh’s higher winter temperatures.

Overall, Banan City experiences higher annual energy use due to climatic severity, but its energy performance benefits from thermal insulation and façade design, which help manage peak loads more effectively. In contrast, Noor City’s reliance on mechanical cooling during warmer months, exacerbated by climatic and design limitations, highlights the necessity of thermal barriers and passive design strategies for improving resilience to external heat stress.

4.4. The 2050 Weather Data Scenario

Under the 2050 climate scenario, projected temperature increases of 1.5–2 °C significantly affect energy consumption and cooling loads in both case studies, with Noor City’s case study showing a sharper rise due to the absence of insulation. In July, Noor City’s cooling load increases to 15,901.72 Wh/m², reflecting a 40% rise compared to current conditions. In contrast, Banan City’s case study demonstrates greater energy resilience, with cooling loads in July increasing to 13,385.36 Wh/m², an 18% rise from the current scenario. These differences illustrate the moderating effect of insulation, which reduces the rate of increase in cooling demands under rising temperatures (see Figure 11 for the simulated monthly energy consumption and cooling loads).

Seasonal trends further highlight the impact of insulation. In spring, Noor City’s cooling load rises by 30% in April, reaching 5478.33 Wh/m², compared to a smaller 15% increase for Banan City’s case study, which reaches 6679.52 Wh/m². During peak summer months, the lack of insulation in Noor City’s case study results in higher sensitivity to external heat, causing steeper increases in cooling loads. In transitional months, Banan City’s insulation continues to provide benefits by moderating fluctuations in cooling demand, ensuring more stable energy use year-round.

In summary, the 2050 scenario underscores the critical role of insulation in mitigating the impact of climate change on energy demands. While both case studies experience increased cooling loads, Banan City’s case study benefits from its regulatory requirement for insulation, demonstrating greater energy efficiency and resilience. Noor City’s case study, without insulation, faces a higher rate of increase, emphasizing the need for improved thermal performance measures to adapt to future warming conditions.

4.5. The 2080 Weather Data Scenario

By 2080, projected temperature increases of 2.5–3 °C result in substantial rises in energy consumption and cooling loads for both case studies, with the effects being more pronounced in Noor City’s case study due to the lack of insulation. In July, cooling loads for Noor City’s case study rose to 19,127.41 Wh/m², representing a 69% increase compared to current conditions. Conversely, Banan City’s case study, benefiting from insulation, shows a more moderate rise in cooling loads to 14,869.19 Wh/m², reflecting a 32% increase. This comparison highlights the long-term advantages of insulation in slowing the growth of energy demands under extreme temperature conditions. See Figure 12 for the simulated monthly energy consumption and cooling loads.

Seasonal variations further emphasize the differences between the two case studies. In cooler months like January, Noor City’s case study shows minimal cooling loads of 32.27 Wh/m², while Banan City’s case study records 884.98 Wh/m², reflecting Riyadh’s warmer winter baseline. During peak summer, Noor City’s lack of insulation leads to significantly higher sensitivity to external temperature increases, resulting in steeper rises in cooling demands. In contrast, Banan City’s insulation continues to mitigate heat gain effectively, ensuring a slower rate of increase across all seasons.

In summary, the 2080 scenario highlights the growing importance of insulation as an adaptive measure for buildings facing rising temperatures. While both case studies exhibit increased energy demands, Banan City’s case study demonstrates greater energy resilience due to its compliance with insulation standards. Noor City’s case study, lacking such measures, faces unsustainable increases in cooling loads, underscoring the need for robust thermal performance standards to enhance climate resilience in residential buildings.

4.6. Code-Swapping Scenarios: Isolating the Influence of Building Codes

To directly address the influence of building code requirements on energy performance, additional simulations were conducted using a code-swapping approach. In this scenario, the Saudi Building Code parameters, lower window-to-wall ratio (WWR), enhanced insulation, and double-glazed windows were applied to the Noor City case study. Conversely, the Egyptian code parameters, higher WWR, uninsulated walls and roofs, and single-glazed windows were applied to the Banan City case study.

Table 6. Code-swapping characteristics applied.

Case Study	WWR (%)	Wall U-Value (W/m2·K)	Roof U-Value (W/m2·K)	Glazing Type
Noor (Egyptian Code)	17.6	0.955	0.256	Single-Glazed
Noor (Saudi Code)	10.52	0.353	0.183	Double-Glazed
Banan (Saudi Code)	10.52	0.353	0.183	Double-Glazed
Banan (Egyptian Code)	17.6	0.955	0.256	Single-Glazed

summarizes the key building envelope characteristics applied in each code-swapping scenario.

The annual energy consumption results are presented in

Table 7. Annual energy consumption under code-swapping scenarios.

Case Study	Code Applied	2023		2050		2080
		Energy Usage (kWh)	Cost (USD)	Energy Usage (kWh)	Cost (USD)	Energy Usage (kWh)	Cost (USD)
Noor	Egyptian Code	319,068	12,443	404,001	15,756	492,403	19,203
	Saudi Code	191,013	7449	239,450	9338	285,574	11,137
Banan	Saudi Code	392,493	22,764	464,359	26,933	521,121	30,225
	Egyptian Code	572,429	33,200	695,005	40,310	797,258	46,241

Note: Egypt’s energy rate = USD 0.039/kWh [47]; Saudi Arabia’s energy rate = USD 0.058/kWh [48].

. Noor City’s energy demand decreased significantly under Saudi code parameters, while Banan City’s consumption increased substantially when subjected to Egyptian code parameters.

The economic implications of these code-swapping scenarios further emphasize the influence of building codes on operational costs. Applying Saudi code measures to Noor City results in significant cost savings, reducing annual energy expenses by approximately 40% across all future scenarios. Conversely, applying Egyptian code parameters to Banan City leads to a substantial increase in annual energy costs, rising by over 50% by 2080 compared to the Saudi code-compliant case. These monetary differences underscore the long-term economic benefits of stringent energy codes.

However, the adoption of such energy-efficient measures entails an initial capital investment, particularly for insulation and high-performance glazing, which can pose economic challenges, especially in lower-middle-income countries like Egypt. While Saudi Arabia’s higher income levels and supportive policies facilitate these investments, Egypt’s economic constraints and housing affordability challenges often hinder the enforcement of advanced energy codes. While this study does not include a full life cycle cost (LCC) analysis, the energy savings demonstrated in the simulations suggest potential long-term operational benefits. For instance, the cost difference observed in Noor City between Egyptian and Saudi code applications translates to cumulative savings of over USD 8000 annually by 2080. Over a typical building lifespan of 30 years, these savings can significantly surpass the upfront costs of implementing insulation and efficient glazing. This analysis demonstrates that despite economic barriers, investing in energy-efficient building codes offers substantial financial benefits over time. Therefore, integrating life cycle cost assessments into policy frameworks is essential for promoting code adoption, providing evidence-based justification for initial expenditures, and aligning energy efficiency goals with economic realities in both Egypt and Saudi Arabia.

4.7. Discussion of the Results

The comparative analysis of Noor City’s and Banan City’s case studies across current and projected climate scenarios underscores the substantial impact of climate, building design, and regulatory standards on energy performance. The trends observed highlight both the immediate and long-term effects of climate change on energy demands, specifically cooling loads, emphasizing the role of insulation in moderating these demands under increasingly extreme temperatures.

4.7.1. Seasonal Energy and Cooling Load Variations

Under current climate conditions, Noor City benefits from Cairo’s milder weather, maintaining lower energy consumption and cooling loads for most of the year. In January, Noor City’s total energy use is 3843.63 Wh/m², with minimal cooling loads of 2.72 Wh/m². In contrast, Banan City, reflecting Riyadh’s warmer winter climate, records a higher cooling load of 173.08 Wh/m², marking 97% greater demand compared to Noor City. This highlights how climate alone significantly affects baseline energy needs. As temperatures rise into spring, both case studies see notable increases. By June, Noor City’s total energy use reaches 10,262.05 Wh/m² with cooling loads of 8219.91 Wh/m²—an increase of approximately 167% from January. Banan City’s total energy reaches 13,200.04 Wh/m², with cooling loads of 10,498.13 Wh/m², a 208% rise from January, despite the moderating impact of its insulation. During peak summer, the effects of extreme heat intensify. In July, Noor City’s energy use climbs to 13,408.26 Wh/m², with cooling loads of 11,338.51 Wh/m²—a 33% increase from June. Banan City shows a smaller increase, reaching 14,061.48 Wh/m² in total energy and 11,293.39 Wh/m² in cooling loads, marking only a 7% rise, check Figure 13. This smaller increment underscores how insulation effectively mitigates additional cooling demand under extreme heat conditions.

4.7.2. Impact of Projected Climate Scenarios for 2050 and 2080

The projected climate scenarios for 2050 and 2080 reveal critical insights into the vulnerabilities and strengths of each case study under sustained temperature increases. By 2050, both Noor City’s and Banan City’s case studies will experience a marked rise in energy consumption, particularly in cooling loads. These increases are a direct response to the anticipated temperature rise of approximately 1.5–2 °C by 2050, with an even greater increase of 2.5–3 °C expected by 2080. This shift underscores the cumulative energy impact that climate change could impose on residential buildings, especially in regions with warm or arid climates.

In the 2050 climate scenario, Noor City’s case study in Cairo shows a significant increase in total energy use, with a notable rise in cooling loads across all months. By July, Noor City’s case study reaches a cooling load of 15,901.72 Wh/m², a 40% increase over the current scenario’s July cooling load of 11,338.51 Wh/m². This increase highlights the vulnerability of uninsulated buildings to climate-driven temperature escalations, as the building’s internal environment relies heavily on mechanical cooling to counteract the rising external temperatures (see Figure 14).

In contrast, Banan City’s case study in Riyadh shows a more controlled increase in cooling loads under the 2050 scenario, with July cooling demands rising to 13,385.36 Wh/m², an 18% increase from the current July load of 11,293.39 Wh/m². While the increase is still substantial, the 18% rise compared to Noor City’s 40% illustrates the benefits of insulation in slowing the rate of energy demand growth (see Figure 15). Banan City’s case study thus exhibits greater resilience, likely due to the polystyrene insulation in its walls and roof, which effectively reduces heat gain and maintains a more stable indoor temperature relative to Noor City’s uninsulated structure.

The 2050 scenario highlights insulation’s moderating effect on seasonal energy demands. In April, Noor City’s cooling load rises by 30% to 5478.33 Wh/m², while Banan City records a smaller 15% increase, reaching 6679.52 Wh/m² from 5986.56 Wh/m². This demonstrates how insulated structures maintain more stable indoor conditions despite rising ambient temperatures. By 2080, these differences become more pronounced. Noor City’s cooling load surges by 69% in July, reaching 19,127.41 Wh/m², compared to 11,338.51 Wh/m² currently, illustrating the heavy burden on uninsulated buildings under extreme heat. In contrast, Banan City’s July cooling load increases by only 32%, from 11,293.39 Wh/m² to 14,869.19 Wh/m², reflecting insulation’s enduring role in mitigating peak demands. Seasonal variations further emphasize these effects. In January 2080, Noor City’s cooling load remains low at 32.27 Wh/m² with a modest 15% increase, while Banan City’s January load rises significantly by 78% to 884.98 Wh/m², driven by Riyadh’s warmer baseline climate. Similarly, in transitional months like April 2080, Noor City’s cooling load increases by 43%, whereas Banan City’s increases by only 20%, underscoring insulation’s effectiveness in reducing HVAC burdens across seasons (Figure 16). Overall, the 2050 and 2080 scenarios confirm that insulation significantly enhances energy resilience in hot climates. Noor City, lacking insulation, faces unsustainable cooling load increases, while Banan City’s insulated design shows a slower rate of increase. These findings support the adoption of mandatory, cost-effective insulation standards—complemented by comprehensive life cycle cost (LCC) analyses—to guide implementation in regions like Egypt, where such measures could play a critical role in mitigating the long-term energy impacts of climate change.

4.8. National Increase in Energy Demand and Associated Carbon Emissions

The analysis reveals contrasting energy and emission trajectories between Riyadh and Cairo (

Table 8. City-wide residential energy consumption and CO₂ emission projections.

City	Year	Case Study Energy (kWh)	City Residential Energy (GWh)	CO₂ Emissions (Million Tons)
Riyadh	2023	392,493.46	42,975.0	293.4
	2050	464,359.65	50,843.8	347.2
	2080	521,121.04	57,058.7	389.6
Cairo	2023	319,068.68	18,612.06	127.3
	2050	404,001.12	23,566.38	161.2
	2080	492,403.69	28,723.12	196.4

). Riyadh’s regulated building codes, emphasizing insulation, result in slower demand growth despite higher initial consumption. In contrast, Cairo’s weaker regulations lead to accelerated energy and emissions increases, nearly doubling Riyadh’s rate by 2080. This disparity underscores how stringent building standards mitigate climate impacts, while lax policies exacerbate strain on infrastructure and decarbonization efforts. The findings emphasize the critical role of energy-efficient codes in aligning urban development with climate resilience in hot–arid regions.

5. Actionable Insights and Recommendations

5.1. Impact on Building Codes and Insulation

The comparative and code-swapping analyses of Noor City and Banan City underscore the pivotal role of building envelope requirements, particularly insulation and the window-to-wall ratio (WWR), in shaping a building’s energy resilience under current and future climate conditions. In Saudi Arabia, mandatory insulation measures significantly reduce heat transfer, stabilize indoor temperatures, and lower HVAC loads. In contrast, Egypt’s regulatory framework lacks such mandates, leaving buildings more sensitive to temperature extremes. This contrast is clearly demonstrated through the code-swapping simulations. When the Saudi code envelope was applied to Noor City, annual energy consumption was reduced by over 40% across all climate scenarios. Conversely, applying the Egyptian envelope to Banan City resulted in a 46:53% increase in energy consumption. These results confirm that differences in code requirements, rather than building form or climate alone, drive substantial variations in energy performance. The lower WWR required by the Saudi code minimizes solar heat gain, while the Egyptian code allows for higher WWRs, which contribute to elevated cooling loads. The results of the solar exposure analysis (Section 3.2) reinforce this effect.

The economic analysis further illustrates these regulatory effects. Applying Saudi code specifications to Noor City resulted in operational cost reductions of over USD 8000 annually by 2080, while the Egyptian envelope led to notably higher operating costs in Banan City. While this study does not include a full life cycle cost (LCC) analysis, these findings point to the potential economic advantages of code-driven energy savings. However, we emphasize the need for future work to assess cost-effectiveness using full LCC methodologies.

In light of these findings, we recommend that Egyptian building codes incorporate insulation and WWR standards tailored to the country’s climatic conditions and supported by rigorous economic feasibility assessments. Such enhancements would contribute to reducing peak cooling loads, enhancing indoor thermal comfort, and advancing national energy sustainability objectives.

5.2. Lack of Renewable Energy Integration in Design Codes

Despite significant advancements in building standards and energy efficiency measures, the integration of renewable energy systems into building design codes remains limited in both Saudi Arabia and Egypt. Current codes emphasize energy efficiency measures, such as insulation and optimized window-to-wall ratios, yet they do not mandate the inclusion of decentralized renewable energy technologies, such as rooftop photovoltaic (PV) systems or solar thermal panels. This omission represents a critical gap in the sustainability strategies of these countries, particularly given the growing energy demands driven by increased cooling loads in hot climates.

Simulations comparing the net site energy consumption of both the Banan (Riyadh) and Noor (Cairo) models, evaluated with and without PV cells, further underscore the potential benefits of integrating renewable energy into the building envelope. The integrated PV system was assumed and sized at 20.48 kWp using monocrystalline silicon panels with an efficiency of 18% under standard test conditions. The system’s energy yield was modeled with a grid-tied inverter (96% efficiency), accounting for 8% losses from temperature derating, wiring, and soiling, and optimized using location-specific irradiance data and a tilt angle of 25° for both Riyadh and Cairo. Simulation results are summarized in

Table 9. Simulation results for each scenario with and without PV cells.

	2023 Scenario		2050 Scenario		2080 Scenario
	Energy Consumption Without PV Cells (Wh/m2)	Energy Consumption with PV Cells (Wh/m2)	Energy Consumption Without PV Cells (Wh/m2)	Energy Consumption with PV Cells (Wh/m2)	Energy Consumption Without PV Cells (Wh/m2)	Energy Consumption with PV Cells (Wh/m2)
Noor model, Egypt	80,756.43	55,146.03	102,252.87	77,401.67	124,627.61	99,531.51
Banan model, Saudi	100,587.76	65,162.22	119,005.54	83,232.44	133,552.29	97,624.29

.

The integration of PV cells leads to substantial reductions in net site energy consumption for both case studies. For instance, in the 2023 scenario, the Banan model shows a reduction of approximately 35,425.42 Wh/m² (a reduction of about 35%), while the Noor model exhibits a reduction of around 25,610.47 Wh/m² (approximately 32%). Although the percentage reductions slightly decrease in future scenarios, indicating that the benefits of PV integration may be moderated as overall energy demands rise, the absolute energy savings remain significant. This trend persists through the 2050 and 2080 projections, demonstrating that renewable energy systems can provide consistent and measurable reductions in energy consumption over time. Moreover, the efficiency of PV systems is highly sensitive to design parameters, such as orientation, tilt angle, and shading. In this study, systems were simulated under optimal conditions, with a 25° tilt and unobstructed solar access, which are typical for maximizing annual yield. However, deviations from these settings, such as east–west orientations or partial shading due to nearby structures, can reduce energy output by 10–30% based on prior empirical studies [49]. Therefore, local implementation strategies should incorporate site-specific optimization to ensure the projected energy savings are realistically achieved in residential deployments.

These findings highlight the substantial impact that mandatory integration of renewable energy technologies could have on reducing the energy footprint of residential buildings. Incorporating requirements for rooftop PV systems and solar thermal panels into building codes could offset a significant portion of the cooling-related energy demands, thereby enhancing the overall sustainability and resilience of the built environment. In the context of both Saudi Arabia and Egypt, where climate change is projected to intensify energy consumption patterns, updating building codes to include renewable energy provisions represents a critical strategy for long-term energy sustainability.

Despite the demonstrated energy-saving potential of PV integration, its widespread adoption in the residential sector remains constrained by the local policy landscape. Both Saudi Arabia and Egypt benefit from high solar irradiance levels, making PV systems technically viable for household use. Economically, the declining cost of PV panels and improvements in system efficiency have enhanced their feasibility; however, the lack of robust financial incentives, such as feed-in tariffs or targeted subsidies for residential installations, limits widespread adoption. Current frameworks, while aligned with national sustainability goals like Saudi Vision 2030, require further regulatory and financial support to mainstream household PV integration.

6. Conclusions

The main aim of this research was to evaluate the influence of regional building codes on the energy performance and cooling load sensitivity of residential developments under climate change conditions using two comparable case studies: Noor City in Cairo and Banan City in Riyadh. Through DesignBuilder simulations incorporating climate projections based on the RCP 4.5 scenario for 2050 and 2080, followed by comparative analysis and code-swapping analysis that assessed the role of envelope design parameters, particularly insulation and the window-to-wall ratio (WWR), we assessed energy consumption trends in hot–arid regions.

The results clearly demonstrate that the stringent insulation and WWR standards mandated under Saudi Arabia’s building codes significantly mitigate cooling load increases. In contrast, the absence of insulation and higher WWR allowances under Egyptian codes led to steeper energy demand growth in Noor City. Solar exposure simulations revealed that Banan City’s façades receive substantially higher solar radiation due to limited shading and greater surface exposure, contributing to elevated cooling loads. These findings emphasize the importance of integrating passive shading strategies into future building code development as a complementary measure alongside insulation.

The code-swapping analysis provided additional validation by isolating the performance impact of regulatory parameters. Applying Saudi code specifications to Noor City yielded substantial energy savings, while the application of Egyptian code parameters to Banan City resulted in significantly increased energy demand. These simulations revealed differences of up to 40–50% in annual energy consumption, underscoring the critical role of building codes in enhancing energy resilience.

An economic comparison based on operational energy costs also demonstrated notable savings when Saudi code measures were applied in the Egyptian context. However, it is important to note that the current study did not include a full life cycle cost (LCC) analysis involving discounting or detailed payback period modeling. Therefore, while the operational benefits are promising, the feasibility of implementation must be interpreted with caution, particularly in lower-income contexts, such as Egypt, where initial investment barriers may be significant. A comprehensive LCC assessment is strongly recommended in future research to fully evaluate the economic viability of such strategies.