Reducing Cooling Energy Demand in Saudi Arabian Residential Buildings Using Passive Design Approaches

Abstract

In Saudi Arabia’s hot and arid climate, residential buildings account for over half of national electricity consumption, with cooling demands alone responsible for more than 70% of this use. This paper explores the hypothesis that contemporary villa designs are inherently inefficient and that current building regulations fall short of enabling adequate thermal performance. This issue is expected to become increasingly significant in the near future as external temperatures continue to rise. The study aims to assess whether passive design strategies rooted in both engineering and architectural principles can offer substantial reductions in cooling energy demand under current and future climatic conditions. A typical detached villa was simulated using IES-VE to test a range of passive measures, including optimized window-to-wall ratios, enhanced glazing configurations, varied envelope constructions, solar shading devices, and wind-tower-based natural ventilation. Parametric simulations were conducted under current climate data and extended to future weather scenarios. Unlike many prior studies, this work integrates these strategies holistically and evaluates their combined impact, rather than in isolation while assessing the impact of future weather in the region. The findings revealed that individual measures such as insulated ceilings and reduced window-to-wall ratios significantly lowered cooling loads. When applied in combination, these strategies achieved a 68% reduction in cooling energy use compared to the base-case villa. While full passive performance year-round remains unfeasible in such extreme conditions, the study demonstrates a clear pathway toward energy-efficient housing in the Gulf region.

1. Introduction

Recent projections suggest a global temperature rise of up to 1.5 °C by the early 2030s, driven largely by increasing energy demand worldwide [1]. In Saudi Arabia, this issue is particularly critical due to its hot, arid climate, where buildings consume approximately 75% of total electricity, with half of this attributed to the residential sector alone [2,3]. Over the past two decades, rapid urbanization across the Gulf region has given rise to entire cities in desert environments, accompanied by an annual increase in power consumption of up to 13.3% [4]. Saudi Arabia is the second-largest energy consumer in the Gulf and the eleventh globally. This growth has often occurred without adequate attention to cultural or environmental considerations, resulting in poorly planned buildings with low energy efficiency [5,6].

The widespread use of air conditioning, now employed daily by over 70% of the population, underscores the region’s heavy dependence on mechanical cooling to achieve indoor comfort [7,8,9]. Yet energy-efficient design remains a secondary priority in most residential developments, which are frequently shaped by client-driven specifications rather than climate-responsive performance. As a result, many buildings experience significant temperature discrepancies between indoor and outdoor environments, contributing to thermal discomfort and increased energy consumption, especially during the summer months [10,11,12]. Given the accelerating pace of climate change and rising energy demands, it is essential to explore passive design strategies that can reduce reliance on mechanical systems and enhance thermal comfort in Saudi Arabia’s residential sector.

1.1. Passive Cooling and Causes for Overheating in Buildings

Before the advent of modern mechanical cooling systems, traditional buildings in hot climates applied passive design strategies to create comfortable indoor thermal conditions [13]. Passive measures, which enhance building performance without relying on mechanical systems, are particularly effective in hot arid climates. Among these, passive cooling strategies aim to maintain indoor comfort with minimal to no energy consumption. Research consistently demonstrates that implementing such approaches can significantly reduce cooling loads before active systems are required.

Proper orientation is essential for minimizing solar heat gain in hot desert climates. Reducing exposure on the east and west façades helps limit the impact of low-angle sunlight during morning and afternoon hours. Studies have shown that building orientation and proportions significantly influence cooling energy demand [14,15]. For instance, unshaded southern façades can raise indoor temperatures by up to 3 °C during summer months [16]. Although the influence of building form is less direct than that of insulation or shading, a well-designed form can still provide passive thermal buffering for interior spaces. Shading windows and walls is one of the most effective passive strategies to reduce unwanted solar heat gain. Without shading, windows absorb only 5–6 percent of solar radiation, with most of the heat transmitted indoors, leading to increased cooling loads. By blocking direct sunlight before it reaches the glass, solar heat gain can be reduced by up to 80%, improving indoor thermal comfort. Exterior shading dissipates heat, whereas indoor blinds trap it [6,17]. In Saudi Arabia’s desert climate, optimized shading was shown to reduce annual cooling energy use by approximately 6.6% [18], while a simulation study in Jeddah reported a 21–37% reduction in cooling demand when shading was combined with other passive measures [19]. However, if poorly designed, shading can obstruct daylight and views, which is why solutions like perforated screens or adjustable louvers are often preferred.

Thermal mass, using materials such as concrete, brick, or adobe, was traditionally used in hot-dry regions to help regulate indoor temperatures. These materials absorbed heat during the day and released it at night, moderating temperature fluctuations [20]. Studies in hot-arid climates have shown that increasing thermal mass can significantly reduce reliance on mechanical cooling by lowering cooling energy use [21]. Clay Bricks are preferred in Saudi Arabia for superior energy performance and cost efficiency, consuming 16% less energy than concrete, 23% less than lime bricks, and 25% less than prefabricated walls. They also delay heat transfer by over an hour [22]. High-mass construction must be paired with proper insulation and cooling strategies; otherwise, it can store unwanted heat. Without measures like night purge ventilation, the delayed release of stored heat may coincide with evening occupancy, leading to discomfort [20]. Thus, thermal mass should be used in tandem with ventilation strategies and proper insulation to yield net benefits. Exploiting cool breezes through cross-ventilation or architectural elements like wind towers can reduce reliance on air-conditioning during milder periods. Wind towers, a traditional feature of Gulf architecture, have been recognized for their passive cooling potential [23,24,25], with studies reporting air temperature reductions of 13% to 16% [26,27]. Research has shown that even with low outdoor wind speeds, wind towers can provide effective ventilation in residential settings, making them suitable for hot and humid climates where mechanical air-conditioning is limited or unavailable [28]. However, there is a lack of quantitative analysis on the energy savings they offer, particularly when integrated with other systems [25]. While extremely effective in the pre-AC era, natural ventilation alone cannot maintain comfort during peak summer weeks when outside air is simply too hot; especially with rising temperatures.

The roof is often the most solar-exposed surface on a low-rise house, so roof treatments are vital. This directly cuts heat gain into the building. Research in hot climates has documented significant cooling energy savings from cool roofs, though specific Gulf-region studies are fewer. A study in Riyadh compared a vegetated roof to a conventional roof and found the green roof cut air-conditioning energy use by 12–33% (varying with irrigation levels and plant cover) [29]. Another experiment in Jordan saw about 17% savings in HVAC energy with even a simple green roof setup [30]. In practice, green roofs might be more feasible for larger-scale projects or as part of broader sustainability initiatives (e.g., using recycled grey water for irrigation). For typical residences, a cool roof or added conventional insulation may be more practical, but green roofs remain an intriguing option that also improves urban greenery.

Enhancing the thermal performance of the building envelope is fundamental to energy-efficient design in hot arid climates [31]. In Saudi Arabia, where many homes were built without insulation, a survey of over 100 houses found that insulated walls and roofs reduced electricity use by an average of 32% [32]. This real-world evidence, supported by simulation studies, confirms that proper insulation significantly lowers both annual cooling loads and peak energy demand. Studies across hot regions [33,34,35] have identified optimal insulation thicknesses that balance energy savings and cost, with approximately 7.8 cm of polystyrene found to be ideal for Riyadh’s climate [36]. Beyond this, additional insulation yields minimal benefit [18]. Polyurethane board was found to be the most effective thermal insulation for hot climates, with only a 1.2% variation in average monthly energy demand, outperforming other materials [37]. As a result, building codes in Saudi Arabia, the UAE, and other Gulf countries now mandate minimum insulation levels for new construction. However, many older homes built without insulation still require retrofitting, a process that can be costly and disruptive but has shown strong returns on investment in case studies. Insulation placement within wall construction significantly affects thermal performance. In hot climates, it is generally more effective to place insulation on the exterior, allowing the internal thermal mass to help stabilize indoor temperatures. Some studies have examined distributing insulation in multiple layers with air gaps, finding marginal gains of 1–3% in energy savings compared to a single thick layer, though these improvements may not justify added construction complexity [36]. Crucially, insulation strategies must be tailored to local climate conditions. For example, Jeddah’s humid climate requires slightly thinner insulation than Riyadh’s due to its lower temperature fluctuations [38], reinforcing that a universal approach is not suitable.

Windows are among the weakest thermal components in building envelopes, particularly in hot climates where single-pane, metal-framed windows (common in older Middle Eastern homes) permit significant solar heat gain [39]. Upgrading to double-glazed windows filled with air or gas can reduce the U-value by half, and adding low-emissivity coatings enhances this further, improving thermal efficiency by 14–16% [40,41]. In hot arid regions, reducing the solar heat gain coefficient is just as important as lowering U-values. Studies show that switching from single clear glass to high-performance glazing can reduce annual cooling loads by 5–7% and cut peak cooling demand by up to 40% [18,42,43]. In one case, replacing a single-glazed window with a triple low-e unit led to a 5.2% energy reduction [18]. A comparative analysis between Riyadh and Jeddah found that window upgrades offered the highest individual savings among envelope improvements- up to 27%, slightly outperforming roof insulation [38]. While improvements from single to double glazing deliver significant efficiency gains, further enhancements like triple glazing or multiple coatings offer diminishing returns. Beyond glazing type, optimizing window area, placement, and shading can yield even greater savings. Energy demand rises as the window-to-wall ratio (WWR) exceeds 20% [44,45,46].

Even efficient equipment can consume more energy than intended if not properly controlled. Occupant surveys in Saudi highlighted behaviours like leaving AC on all day even when out (to avoid a hot home on return) [47,48]. To address this, recent studies have explored the impact of smart thermostats, occupancy sensors, and user behaviour. One study conducted in the UAE investigated smart thermostats that automatically raised the setpoint temperature when occupants were away and found that this approach led to substantial cooling energy savings without significantly affecting occupant comfort [49]. While such measures fall outside typical engineering studies, they address a common challenge: the performance gap between design efficiency and actual usage. A highly efficient villa can still consume excessive energy if occupants set the thermostat to 18 °C and run it 24/7. Thus, the human factor is crucial.

1.2. Climate, Design & Energy Efficiency in Saudi Arabian Residential Buildings

The Koeppen-Geiger Climate Classification categorizes Riyadh as a hot-dry desert subzone, characterized by intense direct solar radiation, clear skies, and minimal cloud cover. The study analysed hourly weather data from Ladybug [50] on Climate Consultant. Data retrieved saw air temperatures with highs of up to 50 °C due to strong surface heating. Summer winds, mainly from the north, are ideal for passive ventilation and cooling. Wind speeds generally exceed 3 m/s, peaking at 10.0 m/s in June. Riyadh’s location in the northern hemisphere results in a predominantly sunny climate with minimal cloud cover, leading to substantial solar radiation, surface heating, and higher air temperatures. The highest global radiation levels occur from May to September, peaking in June (Figure 1). Riyadh’s dry bulb temperature remains within the comfort range of 18–27 °C for less than half the year- during winter and early spring. The hottest periods lie between May to September with temperature highs of up to 47 °C [50].

1.3. Analysis and Framework for a Typical Saudi Arabian Villa

Residential buildings in Saudi Arabia encompass a combination of four-storey apartment blocks, two-storey apartment blocks, duplexes and villas [51]. A ’villa’ denotes a detached building available in various sizes. It constitutes approximately 29% of the total housing units constructed in Saudi Arabia and is the predominant housing type in Riyadh, making up 45% of the housing units [52]. To assess thermal comfort, a base case of a typical Saudi villa with standard construction and features was analysed. This involved examining architectural elements such as wall systems, slab types, doors, and windows. In a study conducted in the Dhahran region, a sample of 200 villas was selected, and their defining features were documented. A typical villa consisted of two floors, with windows uniformly distributed across all sides of the building [53]. Orientation was generally random, although a southern orientation was most commonly assumed. Window sizes also varied, ranging between 0.6 and 3 m, with 1.2 m being the most frequently used. Another study analysing housing in the same region collected data from 300 houses in Dhahran. The findings indicated ceiling heights of approximately 3.3 m, window-to-wall glass areas averaging 13.3 percent, and widespread use of concrete for ceiling and wall construction [54]. This random sample informed the construction, materiality, size, and finish of the representative ’typical villa’ used in this study [55]. Walls were generally composed of concrete block units, with 39 percent incorporating insulation and 32 percent constructed using a cavity wall system. Concrete hollow blocks measured 20 × 20 × 40 cm. Intermediary slabs were constructed using the ’Hordi’ technique, consisting of 30 cm thick concrete. Windows were either single or double-glazed; the latter typically used a 6 × 6 × 6 mm glass-air-glass configuration [55].

1.4. Energy Efficiency in the Region

In 2010, Saudi buildings contributed to approximately 65 percent of the total electricity consumption, which is 47 percent higher than the global average for that period [56]. A study done a mere ten years later saw buildings consume 75% of energy generated, with the residential sector accounting for 48.9% of this consumption; a 10% spike within a decade [2]. Previous research has indicated that villa-type dwellings in Saudi Arabia have an annual average energy consumption ranging from 110 to 227 kWh/m²/year [19]. According to a representative from the Saudi Electricity Company, energy demand was projected to triple from 46,000 megawatts in 2010 to 120,000 megawatts by 2032 if current trends continued [51]. To address rising energy demand, Saudi Arabia introduced new building codes aimed at improving energy efficiency [57]. The Saudi Building Code (SBC), established in 2007 and based on the International Code Council (ICC), set national construction and technical standards. Among its provisions was SBC 602 (Saudi Building Code for Energy Conservation in Low-Rise Residential Buildings), which outlined minimum prescriptive and performance-based requirements for energy-efficient building envelope design [58,59]. The building code specified different minimum U-values based on climatic zones. For example, Zone 1 (Riyadh) required walls to have a U-value no greater than 0.342 W/m²K and roofs no greater than 0.202 W/m²K, while Zone 3 (Abha) allowed slightly higher limits of 0.43 W/m²K for walls and 0.273 W/m²K for roofs. Additionally, all new constructions were mandated to incorporate continuous insulation in accordance with the standard [59].

1.5. Energy-Efficient Projects Within the Region

A few exemplar projects (explored in

Table 1. Case study on energy efficient structures (Passivhaus) within the region.

Project	Building Specifications	Ref.
Qatar Passivhaus	Two 200 m2 villas compared: one built to Passivhaus standards (PHV), the other conventional (STV). PHV used 400 mm wall/roof insulation, 200 mm floor insulation, and triple glazing. PHV achieved 66% lower energy consumption than STV due to high thermal resistance and airtightness.	[60,61]
Ecohouse GUTech Oman	Compact cylindrical form cut solar radiation by 30%. Envelope included lightweight concrete-pumice blocks, perlite infill, and compressed earth bricks. Strategic window placement (no east/west openings) supported natural ventilation and daylighting. Cooling demand reduced by 90% vs. standard walls; projected 40% energy savings overall.	[62]
SABIC Home of Innovation: Riyadh	Featured a highly insulated, airtight envelope and 28 kW rooftop solar PV, achieving net-zero energy over 12 months. Used 40% less energy than a typical Saudi home.	[63]
Masdar City Eco-Villa: Abu Dhabi	Used 72% less energy than a typical Abu Dhabi villa. Combined passive design, high-performance insulation, and efficient systems with rooftop solar panels. Achieved 97 kWh/m2/year energy use.	[64]
Beirut Terraces: Lebanon	Passive cooling through staggered floor plates and deep overhangs reduced solar gain. Vegetated terraces improved air quality and microclimate. High-performance façade materials and glazing optimized daylight and thermal comfort.	[65]
Green Social Housing Initiative: Egypt	The apartment buildings were 30% more energy-efficient than standard units. Achieved via optimized orientation, natural ventilation, thicker insulated walls, and rooftop solar PV.	[66]
Hatta Solar Villa: Dubai	Retrofitted 554 villas with rooftop 4.5 kW solar PV systems each. The system generated approximately 3.6 GWh per year in total, reduced grid reliance, and supported Dubai’s 30% demand reduction goal by 2030.	[67]
Trombe Wall Passive Cooling/Heating: Egypt	Retrofited an uninsulated masonry apartment block with nanomaterial-based wall insulation and double-glazed windows reduced total energy use by 47.6%. Wall insulation alone saved 23%, glazing 26%.	[68]
Green Affordable Housing Initiative: Jordan	Retrofitted 48 homes and built 3 new low-cost green homes for vulnerable families. Upgrades included thermal insulation, double-glazing, solar water heaters, low-flow fixtures, and rainwater harvesting. Results saw noticeable energy and water savings, improved comfort, better indoor air quality, and strong community engagement. Recognized as a scalable model for affordable green housing in Arab regions.	[69]
Residential Retrofit Strategy: Jordan	Deep retrofits (insulation, glazing, HVAC, solar water heaters) projected to cut 43% of annual electricity use and reduce national peak demand by 842 MW. Pilot homes showed improved comfort and lower bills.	[70]

) were analysed to understand regional energy efficiency strategies, forming the basis for subsequent parametric simulations. Regional case studies consistently demonstrate that enhanced insulation, airtight construction, and glazing upgrades are among the most effective strategies for reducing building energy consumption. Projects that combined these elements often achieved energy savings ranging from 30 to over 60 percent. Passive design measures, such as compact building forms, strategic window placement, and the use of thermal mass, also played a key role in lowering cooling demand, particularly in hot, arid climates. In the projects reviewed, passive cooling systems were largely absent, despite their strong potential to mitigate overheating and reduce cooling energy demand, particularly in hot and arid climates like that of Saudi Arabia.

1.6. Research Objectives and Novelty

This study addresses the urgent need to improve energy efficiency in Saudi Arabia’s residential sector, particularly within the context of future climate scenarios. Although numerous international studies have explored passive design strategies, there remains a significant gap in region-specific research that holistically assesses their combined impact on cooling demand, especially under extreme heat conditions anticipated in the coming decades. Unlike much of the existing literature, which isolates passive techniques or overlooks future climate conditions, this study evaluates them in tandem and projects their performance across future temperature profiles up to 2080.

A key novelty of this research lies in the integration of modern and traditional passive strategies, ranging from optimized glazing and insulation to wind-tower ventilation, within a simulation framework that accounts for both current and projected climatic realities. Traditional techniques like the wind tower, once common in Gulf architecture, are rarely assessed in modern parametric simulations. This study repositions such methods within a modern retrofit context, testing their viability as part of a future-proof energy strategy. The primary objectives of this paper are to:

• Evaluate how typical Saudi residential villas perform under current and future climatic conditions.
• Assess the effectiveness of various passive and retrofit strategies- including envelope insulation, window-to-wall ratio adjustments, shading, and wind-towers, individually and in combination.
• Determine which combinations yield the most significant cooling energy reductions.
• Compare the energy performance of a standard (base-case) villa to a redesigned model (such that it could be retrofitted) in both present and future climate scenarios.

The central scientific question explored is: To what extent can passive design interventions reduce the cooling energy demand of Saudi residential buildings under both current and anticipated future climate conditions?

2. Methodology

To form the foundational model, the architectural attributes were derived through a thorough examination of qualitative and quantitative data obtained from various papers and publications. The simulation model used in this study was developed as a hypothetical representation of a typical Saudi villa, informed by statistical data and construction characteristics extracted from regional studies and housing surveys. While direct model calibration using real-world monitored data was not feasible due to geographic constraints, data privacy regulations, and limited public access to detailed residential energy datasets in Saudi Arabia, efforts were made to enhance the model’s reliability. Input parameters such as occupancy schedules, construction materials, glazing types, and internal loads were derived from published research conducted within the region. Moreover, the model employed standard EPW files for Riyadh, which have been validated in other peer-reviewed studies using IES-VE and shown to produce outputs consistent with observed energy use trends in similar building typologies [2,71]. Although a full empirical validation was beyond the scope of this study, this alignment with established regional literature helped support the model’s credibility.

2.1. Modelled Typical Villa

The design considerations outlined (

Table 2. Typical Saudi Dwelling Attributes.

Building Parameters	Base Case Assumptions
Location	Riyadh, Saudi Arabia
Height	7.6 m
Storey	2
Form	Rectangular- spread
Typical floor GFA	172 m2
Floor- floor height	3.5
Ground floor planning	Kitchen, living room, bedroom, guest and dining room
First floor planning	Master bedroom, regular bedroom
Window-to-wall ratio	15%
Typical glazed window	1.73 m2
External wall	Concrete blocks (20 cm thick)
Slabs	Concrete (20 cm thick)

) were utilized in the creation of a representative base case villa. The layout of the villa shown in Figure 2 was derived from the Saudi Ministry of Housing [51]. The villa is oriented towards the south. In the context of fenestration, a standard window size of 1.4 × 1.2 m was selected as the baseline case to attain the desired Window-to-wall (WWR) ratio, employing single glazing for the windows. Windows were assumed to be side-hung with an opening aperture of 50%; and configured to remain open throughout the year, closing solely in situations when the internal temperature fell below 18° or the external temperature surpassed the internal. When cooling loads were considered, HVAC was set to automatically turn on if the internal temperature rose above 23 °C. PPD was not considered, as the primary focus of the testing was to evaluate cooling energy use. Temperature data with the HVAC system turned off was used solely to quantify differences in internal temperatures.

Shading was frequently omitted in housing designs and was therefore not incorporated into the base case model. Uninsulated walls, roofs and single-glazed windows were selected due to them being the common construction technique within Saudi Arabian Villas. The walls consisted of 200 mm concrete blocks with cement plaster on both sides, lacking insulation. The single-glazed windows and walls had U-values of 3.072 W/m²K and 5.8 W/m²K, respectively.

2.2. Assumptions

This conceptual generic model served as a test bed for evaluating both thermal comfort and energy efficiency in a typical Saudi Arabian residential context. The model was assessed through dynamic simulations, incorporating systematic modifications to key variables such as construction materials and building components. A range of passive design strategies was applied to assess their impact on cooling performance. These strategies were chosen for their relevance to the regional climate and their proven influence on building energy use, as supported by existing literature. Defining a clear base case was essential, as it served as a consistent reference point for evaluating and comparing the effectiveness of each intervention.

A digital twin of the building was developed using the Integrated Environmental Solutions: Virtual Environment (IES VE) simulation platform, a widely recognized tool for conducting Building Energy Simulations [72]. The tool was selected for analysis due to its capability to quantify improvements across various strategies through its dynamic-state software. IES VE, accredited by the U.S. Department of Energy and compliant with ASHRAE Standard 140, was chosen for its ability to deliver high-fidelity energy and environmental simulations using its ApacheSim thermal engine [73,74,75]. The accuracy and robustness of IES VE have been validated across multiple peer-reviewed studies, confirming its suitability for research and professional applications in the field of building performance analysis [73,76,77]. These validations underscore the software’s reliability in simulating complex thermal and energy dynamics in the built environment.

The analysis involved multiple input parameters, encompassing architectural details, building construction elements, occupancy patterns, schedules, and weather data files (refer to

Table 3. Analysis considerations for dynamic-state modelling.

Occupancy Schedules and Analysis Considerations
Number of occupants	4
Infiltration	0.7 ACH
Sensible loads	Living space: 180 W	Master bed: 80 W	Other bed: 80 W
Lighting power (LED)	2 W/m2
Occupant heat gain	Zone	Sensible heat	Latent heat
	Living	225	165
	Bedroom	150	110
	Kitchen	150	110

and Table 4). The building’s geometry and functional spaces were generated using ModelIT within IESVE. Once the 3D model was established, construction materials and data were incorporated. Multiple rooms were analysed: the living room, master bedroom, and standard bedroom. The following considerations were made when determining factors affecting cooling:

• Although travel restrictions limit direct access to a typical Saudi villa, it is generally acknowledged that residential buildings in Saudi Arabia exhibit moderate infiltration rates. A previous study assumed an Air Changes per Hour (ACH) of 0.7 [78].
• Weather files (EPW) used for testing were based in Riyadh Airport. The chosen EPW file was morphed using CCWeatherGen [79], generating prospective weather conditions based on the climate change projections from 2002 [80]. This facilitated testing parameters against current, as well as future scenarios (2050 and 2080).
• Winter clothing levels were assigned a value of 1, while summer clothing levels received a value of 0.5.

Data and values considered during analysis were referred from CIBSE TM59, analysis of typical Saudi dwellings and similar papers testing various parameters within the region [2]. Surveys conducted [81] helped determine schedules across different spaces. The survey examined space utilization by analysing occupancy timing and monthly levels to accurately assess internal demands. Thermal comfort, influenced by occupant activities and locations, was tested separately in two bedrooms (north- and south-oriented) and the living hall.

Table 4. Schedule of occupancy [81].

	During Weekdays: Hours in the Day
Rooms	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23
Kitchen
Guest
Dining
Living
Bedroom
Empty 1
	During Weekends: hours in the day
Rooms	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23
Kitchen
Guest
Dining
Living
Bedroom
Empty 1

¹ No occupants were present. Fill colour indicates periods occupied.

Table 4. Schedule of occupancy [81].

	During Weekdays: Hours in the Day
Rooms	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23
Kitchen
Guest
Dining
Living
Bedroom
Empty 1
	During Weekends: hours in the day
Rooms	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23
Kitchen
Guest
Dining
Living
Bedroom
Empty 1

¹ No occupants were present. Fill colour indicates periods occupied.

2.3. Framework: Overview of Testing Strategy

To comprehensively evaluate the impact of rising temperatures in a hot arid country like Saudi Arabia, the base case villa was first analysed under both current and projected future weather scenarios. A series of parametric simulations were then conducted to assess the performance of well-documented passive strategies, testing their effectiveness within a modern climatic context. Building on this, the study explored architectural interventions such as solar shading and wind towers, which are known from the literature to mitigate indoor heat gains. Finally, the most effective strategies were synthesized into a hypothetical retrofitted model. This optimized design was tested to determine its energy performance under present conditions and to evaluate its resilience under future climate scenarios. The study follows a four-stage testing framework (refer to Figure 3):

• Baseline Performance Assessment: Evaluation of the base case villa under both current and future weather conditions.
• Engineering-focused analysis: Simulation of envelope components, including glazing, wall construction, and WWR.
• Architectural-focused analysis: Testing of passive cooling features like shading and wind towers.
• Synthesized Retrofit Design: Integration of the highest-performing strategies into a redesigned model, tested for both present-day and future climatic scenarios.

To help better categorise changes and their individual effects on cooling demand, testing parameters were divided into distinct categories labelled PCS1 through PCS5 (refer to

Table 5. Testing Strategy.

PCS 1	Description	Testing Parameter
PCS1	Window-to-wall ratio	20%: Base case
		15%
		10%
PCS2	Fabric	Base-case
		Insulated concrete wall
		Insulated- clay brick wall
PCS3	Glazing	Single glazed: Base case
		Double glazed
PCS4	Shading	Calculate shading
		Crate shading
PCS5	Wind tower	WT1 2: Open wind-tower
		WT2: Split wind-tower
		WT3: Split wind-tower: 3 m shorter
		WT4: Split wind-tower: 3 m taller
		WT5: Split wind-tower: reduced aperture
		WT6: Split wind-tower: closed on the east and west

¹ Passive cooling strategy; ² Wind-tower.

). PCS1 to PCS3 focused on examining engineering parameters, such as alterations of fenestrations or fabric, whereas PCS4 and PCS5 involved making minor interventions to the structures such as the inclusion of shading and wind-towers.

A structured simulation matrix was built by combining variables across WWR (5–20%), wall types (BCT, INC, ICB, TM), and glazing types (SG, DG, AR), resulting in 48 scenarios. Architectural interventions were tested independently on top-performing engineering configurations. All scenarios are labelled using the code format: [WWR]—[Wall Type]—[Glazing] (e.g., 10-TM-DG), enabling easy comparison and cross-referencing throughout the analysis.

2.4. Villa Simulated Base-Case Analysis (Typical Dwelling)

On testing external surfaces, substantial solar exposure was found on all surfaces aside. Subsequent testing revealed that the roof received the highest amount of solar radiation, double that of the walls, followed by the south, east and west. The north exhibited the lowest solar radiation while also having the smallest surface area (Appendix A: Figure A1). An average rise of up to 3 °C was noted within the structure by 2050 and 5 °C by 2080, yielding a net rise of up to 54.68 kW in sensible cooling load—a 38% spike from current (refer

Table 6. Base case villa metrics.

Scenarios	Current	2050	2080
Air temperature (°C)	30.22	33.12	35.16
Total cooling plant sensible load (kW)	89.45	120.67	144.13

). Based on earlier analysis July and August were expected as the hottest months in the region. Subsequent dynamic testing confirmed the earlier analysis, affirming that significant energy would be needed to cool indoor spaces during these months. In contrast, January and December demanded minimal to no cooling (refer to Figure 4).

In hot climates, a true north-south orientation is generally optimal [82]. Orientation was tested in 90° increments to assess thermal impact. Results showed that the south-facing configuration had higher internal temperatures due to extensive glazing. Rotating the building westward improved performance, likely due to reduced solar exposure on critical façades. Overall, north and west orientations performed slightly better, though the differences across orientations were relatively minor.

3. Parametric Analysis via Engineering Parameters

Variations were limited to the external wall, window construction, and window-to-wall glazing percentages. The following engineering parameters were varied and tested: Window-to-wall ratio: Adjustments to glazing were made, varying the WWR through the fabric. The base case featured a WWR of 15%. Aperture sizes were varied at 10% and 5% to explore the impact of reduced openings, while a 20% WWR was also examined to assess potential increases in cooling loads.

Table 7. Window-to-wall ratio and corresponding areas used in testing.

WWR Ratio	5%	10%	15%%	20%
Living room	0.81 m2	1.62 m2	2.42 m2	3.20 m2
Master bedroom	1.05 m2	2.10 m2	3.15 m2	4.20 m2

showcases WWR ratios and their respective window areas used during testing.

Glazing: Glazing varied between single and double-pane windows with U-values of 5.8 W/m²K, 2.7 W/m²K respectively and 1.3 W/m²K with Argon. Triple glazing was omitted due to multiple sources indicating marginal improvements over double glazing within the region. The chosen incremental glazing types (as seen in

Table 8. Varied glazing parameters.

	Single Glazed	Double Glazed	Double Glazed
Thickness	4 mm	24 mm	24 mm
Glass construction (From out to in)	Aluminium Cladding (4 mm) Unventilated Air Cavity (100 mm) Gypsum Blocks (60 × 60 × 10 cm)	Glass (4 mm) Air (16 mm) Glass (4 mm)	Glass (4 mm) Argon (16 mm) Glass (4 mm)
U-Value	2.7 W/m2K	2.7 W/m2K	1.3 W/m2K

) offered a precise assessment of performance, quantifying performance when transitioning from single to double glazing and altering the gas in between.

Building Envelope: This involved optimizing thermal transmittance in the building’s structure through increased thermal mass and insulation. For the opaque elements of the building envelope, improvement was achieved by adding thermal insulation materials to lower thermal transmittance. Material selection was informed by literature and preliminary simulations (see Appendix A: Figure A2). While all tested walls used similar materials, concrete and polyurethane insulation, variations were introduced to assess specific effects. The Insulated Concrete Wall (INC) tested standard insulation performance, with prior studies showing 2–14% energy savings over uninsulated alternatives [37]. The Thermal Mass Concrete Wall (TIC) increased concrete volume to explore the thermal mass impact, while the Reverse Insulated Concrete Wall (ICR) inverted the layer order of INC to expose concrete to the exterior. A Hypothetical Low U-Value Wall (TM) used thicker insulation to push U-values lower. Results (See Appendix A: Figure A3) showed that although INC achieved the lowest internal temperatures, it had the highest cooling load. TM, despite higher internal temperatures, used the least energy when cooling was active, likely due to superior insulation retaining cooled air. TIC and ICR, with higher U-values, still performed efficiently, particularly ICR, which had 2.9% lower mean loads than TIC, though with slightly warmer interiors. These findings underline the nuanced trade-offs between insulation, thermal mass, and material positioning within wall assemblies.

Among the four options, TM was chosen for testing within the matrix because of its energy efficiency. Conversely, INC was selected because it exhibited lower internal temperatures and was deemed a straightforward retrofit solution for construction in the region. The decision to use clay bricks over concrete blocks was based on studies from the literature review which indicated that clay bricks consume less energy. Therefore, the effectiveness of clay bricks in comparison to concrete was to be tested. The highest U-value construction considered in this study (INC) is approximately 27.2% better than the minimum U-values proposed by SBC 602.

Table 9. Varied materiality parameter.

	Base-Case Typical (BCT)	Insulated Concrete (INC)	Insulated Clay-Brick (ICB)	Low U-Value (TM)
Thickness	230 mm	370 mm	320 mm	530 mm
Const.	Cement Plaster (15 mm) Concrete (200 mm) Cement Plaster (15 mm)	Cement Plaster (15 mm) Polyurethane board (90 mm) Concrete (250 mm) Cement Plaster (15 mm)	Cement Plaster (15 mm) Clay Brick (100 mm) Polyurethane board (90 mm) Clay brick (100 mm) Cement Plaster (15 mm)	Cement Plaster (15 mm) Polyurethane board (200 mm) Concrete (300 mm) Cement Plaster (15 mm)
U-Value	2.736 W/m2K	0.249 W/m2K	0.244 W/m2K	0.118 W/m2K

showcases the constructions used for testing within the iterative matrix.

Ceiling: Analysis of the ceiling was not studied as a permutation due to the wall construction being considered as a single unit. The ceiling was instead considered separately. Saudi Arabia enjoys abundant annual solar radiation, with extended daylight hours typically averaging 8.89 h. The ceiling received the majority of solar exposure and radiation (2200 kWh/m² on the roof vs 1100 kWh/m² on the southward wall as per analysis from the base case) due to its high altitude increasing its energy consumption by extension. The following test aimed to quantify the net reduction in energy consumption over the base case when insulation or thermal mass was added (hypothetical construction seen in

Table 10. Hypothetical ceiling construction.

	Insulated Ceiling	Thermal Mass Ceiling
Thickness	472 mm	472 mm
Construction	Gravel bedding (60 mm) Cement plaster (12.7 mm) Polyurethane board (200 mm) Concrete (200 mm) Cement Plaster (12.7 mm)	Layers from outside to inside Gravel bedding (60 mm) Cement plaster (12.7 mm) Polyurethane board (80 mm) Concrete (320 mm) Cement Plaster (12.7 mm)
U-Value	0.110 W/m2K	0.275 W/m2K

). The hypothetical building construction was selected to ascertain whether insulation or thermal mass (concrete) had a more significant impact on enhancing energy efficiency while maintaining cooler indoor environments naturally. The components were kept of equal thickness, with concrete and insulation thicknesses varied. The thermal mass ceiling achieved U-values comparable to those specified in SBC 602.

3.1. Input Parameters & Simulation Matrix

Based on the parameters discussed earlier,

Table 11. Simulation matrix for engineering parameters.

WWR Ratio	Fabric Component	Glazing	Combination
20%	Base case typical (BCT)	Single glazed	20-BCT-SG
		Double glazed	20-BCT-DG
		Doubled glazed Ar.	20-BCT-AR
15%		Single glazed	15-BCT-SG
		Double glazed	15-BCT-DG
		Doubled glazed Ar.	15-BCT-AR
10%		Single glazed	10-BCT-SG
		Double glazed	10-BCT-DG
		Doubled glazed Ar.	10-BCT-AR
5%		Single glazed	5-BCT-SG
		Double glazed	5-BCT-DG
		Doubled glazed Ar.	5-BCT-AR
20%	Insulated concrete (INC)	Single glazed	20-INC-SG
		Double glazed	20-INC-DG
		Doubled glazed Ar.	20-INC-AR
15%		Single glazed	15-INC-SG
		Double glazed	15-INC-DG
		Doubled glazed Ar.	15-BCT-AR
10%		Single glazed	10-INC-SG
		Double glazed	10-INC-DG
		Doubled glazed Ar.	10-INC-AR
5%		Single glazed	5-INC-SG
		Double glazed	5-INC-DG
		Doubled glazed Ar.	5-INC-AR
20%	Insulated clay brick (ICB)	Single glazed	20-ICB-SG
		Double glazed	20-ICB-DG
		Doubled glazed Ar.	20-ICB-AR
15%		Single glazed	15-ICB-SG
		Double glazed	15-ICB-DG
		Doubled glazed Ar.	15-ICB-AR
10%		Single glazed	10-ICB-SG
		Double glazed	10-ICB-DG
		Doubled glazed Ar.	10-ICB-AR
5%		Single glazed	5-ICB-SG
		Double glazed	5-ICB-DG
		Doubled glazed Ar.	5-ICB-AR
20%	Low U-value const. (TM)	Single glazed	20-TM-SG
		Double glazed	20-TM-DG
		Doubled glazed Ar.	20-TM-AR
15%		Single glazed	15-TM-SG
		Double glazed	15-TM-DG
		Doubled glazed Ar.	15-TM-AR
10%		Single glazed	10-TM-SG
		Double glazed	10-TM-DG
		Doubled glazed Ar.	10-TM-AR
5%		Single glazed	5-TM-SG
		Double glazed	5-TM-DG
		Doubled glazed Ar.	5-TM-AR

presents a simulation matrix showing the different combinations tested for the building envelope. Within the naming tag: the initial digit corresponds to the WWR ratio; the letters correspond to the type of construction with the concluding digit denoting the type of glazing selected. For example, the first series of simulations encompass 20-BCT-SG, 15-BCT-SG, 10-BCT-SG, and 5-BCT-SG, which tests the effects of the four diverse WWR ratios (20%, 15%, 10%, 5%) while the building construction and glazing composition are kept consistent the typical base-case typical (BCT) coupled with single glazing.

3.2. Results and Analysis

A permutation of 48 simulations was run, testing different building envelope feature combinations (as seen in Table 11). The thermal simulations evaluated the mean temperature and cooling loads of the hottest space as identified prior—the south-facing master bedroom. The most influential parameter affecting cooling energy loads in the building was identified by determining the best and worst combinations of WWR ratio, wall type, and glazing type.

3.2.1. Evaluating Building Fabric

Table 12. Cooling loads through various envelope combinations in (kW).

Parameter	5%	10%	15%	20%
BCT SG	88.62	89.58	90.58	91.49
BCT DG	85.09	85.35	85.63	85.89
BCT AR	85.04	85.30	85.58	85.83
INC SG	68.87	69.50	70.17	70.81
INC DG	66.18	66.56	66.95	67.32
INC AR	66.13	66.50	66.88	67.25
TM SG	67.89	68.54	69.22	69.86
TM DG	65.18	65.56	65.96	66.34
TM AR	65.13	65.50	65.90	66.27
ICB SG	68.92	69.56	70.23	70.87
ICB DG	66.24	66.61	67.00	67.37
ICB AR	66.18	66.55	66.94	67.30

displays a comparison of the cooling loads of the building for all envelope combinations. The analysis revealed that the combination 5-TM-AR performed the best. This result was expected, given its low WWR ratio of 5% and a glazing type with a lower shading coefficient as seen in

Table 13. Glazing performance.

File	Minimum °C	Maximum °C	Mean °C	Mean Load	Solar Gain
BCT SG	9.76 °C	47.57 °C	30.20 °C	1.295 kW	0.439 kW
BCT DG	9.91 °C	47.01 °C	20.92 °C	1.185 kW	0.202 kW
BCT AR	9.94 °C	47.02 °C	29.94 °C	1.185 kW	0.201 kW

, combined with the thick insulation in the wall type; giving the hypothetical wall its low U-Value.

Conversely, 20-BCT-SG the un-insulated concrete wall with a 20% WWR ratio and higher shading coefficient performed the worst in energy efficiency. The simulations aimed to identify the key engineering parameters affecting the building envelope’s thermal performance. Solar gains notably influenced cooling loads, particularly with single glazing and higher shading coefficients. As the WWR ratio increased from 5% to 20%, solar gains became more significant, especially with higher shading coefficient glazing types like single glazing. TM construction consistently outperformed ICB and INC across all WWR ratios, with a reduction of 0.8–1 kW observed. Adding thermal insulation and adjusting the shading coefficient of glass effectively mitigated solar heat gain, even at higher WWR ratios.

3.2.2. Evaluating Ceiling Performance

The hypothetical building construction was selected to ascertain whether insulation or thermal mass (concrete) had a more significant impact on enhancing energy efficiency while maintaining cooler indoor environments naturally. The components were kept of equal thickness, with concrete and insulation thicknesses varied. The findings (found in Figure 5) indicated that incorporating insulation resulted in a 38% improvement in energy efficiency compared to the base case. A minimal 2.4% decrease in indoor temperatures when the HVAC system was inactive was noted. Although the thermal mass construction exhibited a 22% improvement over the base case, the former was still considered the superior construction method: thereby proving insulation as pivotal in efficiency over thermal mass (concrete).

4. Parametric Analysis via Architectural Parameters

This section shifts from engineering principles to architectural strategies for reducing solar heat gain. Testing for PS5 (solar shading) was conducted without altering the architectural layout, maintaining consistency with the base case in terms of spatial layout, construction materials, and glazing. All thermal loads and internal assumptions mirrored those established in previous sections to ensure comparability. In contrast, PS6 (wind-tower integration) required minor architectural modifications to accommodate the passive ventilation system. While the overall spatial configuration and dimensions were preserved, the model was adjusted to include a wind tower, referenced in this study as configurations WT1–WT6. These adjustments were necessary to meet the specific spatial and airflow requirements of wind-tower-based ventilation.

4.1. Solar Shading

To reduce unwanted solar heat gain through windows, it is important to block direct sunlight using effective shading strategies [83]. Previous research has demonstrated that the inclusion of solar shading devices resulted in a reduction of indoor temperatures ranging from approximately 2.5 °C to 4.5 °C [84]. Shading decisions impact thermal comfort and require rules-of-thumb and design tools for initial evaluation. Effective external shading solutions must consider geographical latitude, sun angles, and annual temperature/radiation peaks [85]. The analysis showed that the south-facing façade experienced the highest solar radiation, with the east and west receiving slightly less. This elevated exposure during the hot months of May to September significantly increased cooling energy demand, highlighting the critical need for effective shading on these sides. Using Equation (1) the options for shading devices were established.

DH = tan (90 − εε) × HW

(1)

DH = Horizontal overhang depth (m) DV = Vertical fin depth (m) HW = Window Height (m).

Evaluating Shading Performance

The hottest period of the year (refer to Appendix A: Figure A4) was considered for shading. Considering that the sun was at lower altitudes on the east and west during the early and late parts of the day, crate shading was examined for its impact on efficiency. The assessment of its effects on internal lighting levels was not significant with most of the room (master bedroom) remaining adequately illuminated throughout the day, regardless of the WWR ratios. The analysis (

Table 14. Shading across various WWRs.

WWR Ratio		5%	10%	15%	20%
BCT SG Base-case	Average	29.78	29.89	30.19	30.37
	Maximum	46.75	47.11	47.57	47.92
	Minimum	9.67	9.79	9.76	9.73
BCT SG Calculated	Average	29.69	29.80	29.93	30.14
	Maximum	46.75	47.11	47.47	47.92
	Minimum	9.57	9.66	9.61	9.55
BCT SG Crate	Average	29.64	29.62	29.79	29.90
	Maximum	46.76	47.1	47.53	47.86
	Minimum	9.42	9.36	9.31	9.35

& Figure 6) examined different WWR ratios for the south-facing master bedroom under varying shading conditions: no shading, overhang and crate shading. Using the base-case structure, shading on the south facade led to slight temperature improvements of 0.15 °C for lower WWR ratios, while higher ratios saw improvements of up to 0.5 °C without cooling. Crate shading showed a temperature savings of 0.2 °C compared to the calculated lateral overhang. With cooling activated, efficiency increased by 5.5% compared to the base case, with minimal differences between the standard calculated overhang and crate shading.

To mitigate heat gain on the east side, substantial fins were required. Testing in the eastward-oriented living room (Figure 7) demonstrated slight improvements across different WWR ratios, with a 0.2 °C temperature difference without cooling and a 0.5% reduction in HVAC load when cooling was active. Due to the sun’s higher altitude for most of the day, further reductions in heat gain through shading may be limited.

4.2. Wind Tower

A wind tower utilizes natural ventilation by harnessing pressure variations around the structure. Therefore, it was crucial to position the device to optimize the pressure contrast between the inlet and outlet [86]. To conduct parametric testing, it was necessary to modify the villa’s design. The spatial layout and dimensions were retained to match the original design. The wind tower was placed with the living room selected as the primary simulation zone. The wind tower was configured according to the specifications outlined in

Table 15. Wind-tower specifications.

Wind Tower Specifications
Tower height	13.3 m
Tower cross section	2.3 × 1.5 m
Wind catcher openings	1.6 × 2.5 m broad end; 1.6 × 1.9 m short end
Intra- floor supply openings	0.7 m × 2.2 m broad end; 0.7 × 1.6 m short end

. The tower’s width was aligned with the prevailing wind direction, ensuring that the broader side of the tower faced the north, where the prevailing winds came from during the summer. At the top of the cooling tower, was a four-sided air inlet opening serving as the wind-tower. In the digital model, the openings were emulated as windows on IES, using a continuous “always on” profile. The research conducted aimed to examine a range of factors influencing wind towers and assess their performance, particularly in terms of efficiency and internal temperatures. These parameters included wind directions, aperture sizes, and heights.

BC served as a base case without a wind tower. WT1 introduced a basic wind tower with a fixed aperture of 16 m² and a height of 13.3 m. Research previously carried out [87] revealed that internal partitions had a notable impact on the effectiveness of ventilation. These partitions divide the wind tower into smaller channels, thereby decreasing its vulnerability to varying wind directions and bolstering the structural integrity of the wind tower. Subsequently, WT2 featured a barrier between the north and south openings, redirecting northward winds into the wind tower. WT2 served as the baseline against which all subsequent wind-tower configurations were compared. WT1 was included to test the effect of removing the internal partition, while BC (the base case without a wind tower) was used to quantify the impact of incorporating a wind tower into the design. WT3 and WT4 investigated the impact of varying heights (increasing and decreasing by ±3 m). In contrast, WT5 reduced the wind tower’s opening size by 40% to 9.7 m², based on the assumption that a larger aperture might increase cooling loads, so reducing it could further reduce the loads. Lastly, WT6 examined the possibility of preventing air from escaping through the west and east sides. The different wind towers tested can be found in Figure 8.

Evaluating Wind-Tower Performance

During the evaluation of the living room, it was observed that BC had an average temperature of 29.78 °C. Cooling requirements remained relatively high at 0.97 kW. The introduction of wind towers resulted in a temperature increase when operated passively. However, when the HVAC system was activated, there was an improvement of 9%. Implementing partitions improved passive temperature control while slightly decreasing cooling loads by approximately 1.5%. Reducing the height by 3 m led to an increase in cooling loads, whereas increasing the height resulted in decreased loads. The initial hypothesis that cooling loads would decrease with smaller apertures proved to be correct. Among the wind towers, WT5 performed the best, with a 40% reduction in aperture size leading to a cooling load reduction of about 30% (listed in Figure 9).

5. Design and Recommendation

The study aimed to explore the potential for reducing energy loads in residential buildings through passive strategies. Although these strategies showed promise individually, it became clear that achieving a fully passive building was not feasible with the methods available- especially considering that future temperatures are projected to be significantly higher than current conditions. As a result, the research focused on identifying effective combinations that could substantially lower cooling demand. To realise the combined benefits of the tested strategies, a new dwelling was designed incorporating the most effective permutations. This model was then compared to the base case to evaluate the overall performance improvements. The house underwent additional testing against future climate scenarios to assess its ability to withstand and adapt to changing conditions, as compared to the base case.

The building was designed with fewer openings on the south and east façades, while windows were positioned on the north to allow diffused light with minimal solar gain. South-facing windows maintained similar dimensions and employed a window-to-wall ratio (WWR) of 10%. Although a 5% WWR proved to be more efficient, the trade-off in terms of outdoor views and occupant satisfaction was considered not worthwhile. In terms of daylighting performance, all window-to-wall ratios were found to provide adequate illumination based on the analysis of Useful Daylight Illuminance (UDI), as shown in Appendix A: Figure A5. Studies on glazing specifications indicated only slight improvements in efficiency when U-values were reduced by incorporating argon, so a standard double-glazing approach was adopted. Shading on the east side was omitted due to the large fins required, which would obstruct views and reduce interior daylight. Instead, south-facing overhangs were used, proving effective in reducing heat gains. Among the various building fabric components tested, the low U-Value TM construction performed the best. An insulated ceiling was also considered, proven to significantly reduce the cooling load. Lastly, a wind tower, specifically WT5, was incorporated into the design of the new simulated villa. While a combination of WT4 and WT5 was considered, the overall reduction in energy loads was not substantial enough to warrant its adoption. As seen in Figure 10 and Figure 11, centrally placed living areas, corridors, master bedroom and guest room were all serviced. The form of the overall building was compacted over the base case, reducing the overall footprint and by extension reducing cooling loads (refer to Appendix A: Figure A6 for CFD analysis).

When examining the cooling loads throughout the month, notable enhancements were observed in comparison to the base case, operating passively for 5 months in contrast to the base case’s 3. Moreover,

Table 16. Base case villa metrics.

Scenarios	Current	2050	2080
Air temperature (°C)	30.22	33.12	35.16
Total cooling plant sensible load (kW)	89.45	120.67	144.13

and

Table 17. Designed villa metrics.

Scenarios	Current	2050	2080
Air temperature (°C)	29.92	32.13	34.15
Total cooling plant sensible load (kW)	28.23	39.53	47.82
Improvement over base case	68.4%	67.24%	66.82%

show that the mean sensible load across the three simulation zones was reduced by more than half compared to the base case. While the passive strategies resulted in only a modest decrease in internal temperatures (0.3 °C), they led to a substantial reduction of over 68% in cooling loads under current climate conditions. Furthermore, the combined strategies resulted in the designed building’s projected cooling loads for 2080 (with a 4 °C hotter climate than current) being 40% lower than the base case’s cooling loads in current scenarios (2020’s). Additionally, future projections saw the building performing up to a degree better than the base case (as seen in Figure 12a,b).

6. Discussion

The surge in energy consumption in the Gulf Region, fuelled by rapid population growth and industrial expansion, particularly in Saudi Arabia’s harsh climate, highlights the urgent need to address energy efficiency in the region. While passive elimination of heat may not be entirely feasible, a combination of passive strategies offers promising avenues for reducing cooling loads. For instance, reducing glazing ratios to 5% showed improved performance; however, the marginal gains (a 3% reduction in loads between 5% and 15% ratios) may not justify the negative impact on aesthetics and user satisfaction. Visual access, daylight, and overall spatial experience are important to occupants and often influence design decisions. This trade-off becomes increasingly relevant as the region faces rising temperatures, which will further amplify cooling demands and place additional strain on mechanical systems, reinforcing the need for balanced, user-conscious passive design. Furthermore, it is also important to note that as external temperatures continue to rise, the effectiveness of passive measures will become increasingly critical. Higher indoor temperatures not only increase discomfort but also place additional strain on mechanical cooling systems, which must operate longer and work harder to maintain acceptable indoor conditions. This highlights the need for more aggressive passive strategies and better-performing envelopes to future-proof buildings in hot climates.

6.1. Limitations

It is important to note that although the improvements are significant and potentially replicable in a real-world building, the study’s limitations are acknowledged and discussed:

• The economic feasibility of retrofitting (particularly for low and middle-income households) poses a substantial barrier. High-performance materials, glazing systems, and structural alterations such as windcatchers or green roofs may involve significant upfront costs that are not immediately recoverable without financial incentives or government subsidies. Cost-benefit analyses and lifecycle assessments should therefore complement technical evaluations in future studies.
• Implementation challenges remain significant. Many of the passive strategies tested here, especially those involving structural redesigns or additions, may face regulatory, architectural, or construction-related obstacles. Builder familiarity and technical capacity are also major limitations. Many construction firms in the region may lack experience with advanced insulation techniques, airtight envelope detailing, or traditional passive systems like windcatchers, which have fallen out of common practice. This skill gap can lead to poor implementation or resistance from developers accustomed to conventional, low-cost construction methods.
• Aesthetic preferences and cultural norms influence design acceptance. Features like reduced glazing, visible shading devices, or rooftop windcatchers may be perceived as unattractive or outdated by homeowners or developers seeking sleek, modern appearances. This aesthetic resistance can be a significant barrier, especially in markets where housing trends prioritize visual appeal over performance.
• Occupant behaviour plays a critical role in the energy performance of buildings. Even the most technically efficient villas can become an energy liability if occupants override thermostats, misuse windows or ventilation systems, or leave cooling units running unnecessarily. Bridging this “performance gap” requires not only smart technologies but also educational efforts to promote energy-aware behaviour among residents.
• Another limitation of this study lies in the assumption of infiltration rates on values derived from previous literature. While these assumptions offered a reasonable starting point and showed limited impact on results compared to other variables in the sensitivity analysis, they may not fully reflect the variability found in real-world conditions. Infiltration rates, for instance, are highly sensitive to construction quality, detailing, and long-term maintenance, factors that differ across projects and are often underrepresented in generalized datasets.

6.2. Future Work

Future work should incorporate monitored data from actual buildings to evaluate performance outcomes within the regional context and to validate the assumptions used in simulation models. While this study focuses on Riyadh it is important to recognize that the strategies and performance levels identified may not be universally applicable across the broader Arab region or even within Saudi Arabia itself. Climatic variation across the region is significant, with some areas characterized by hot-humid conditions and others by hot-arid environments. As such, the scope of future studies should be expanded to include multiple geographic locations, enabling comparative analysis of passive strategies and retrofit effectiveness under varying climatic conditions. Furthermore, the reliance on secondary data introduces a degree of uncertainty, which may result in discrepancies between predicted and actual building performance. Incorporating empirical data from monitored residential projects would not only improve the accuracy of performance predictions but also strengthen the contextual relevance of design recommendations, ultimately supporting the development of more adaptive and climate-responsive building solutions.

6.3. Conclusions

The initial study examined the impacts of placement, thermal mass, and low U-values in the region. Intriguingly, the component with the lowest U-value initially caused the highest interior temperatures, while the simple insulated concrete wall component exhibited the lowest temperatures passively. However, when cooling was activated, the results reversed, with the lower U-value component effectively trapping cool air. Additionally, the introduction of thermal mass proved highly effective, consistent with literature findings. The characteristics of both opaque and transparent elements in the building envelope were found to have a substantial impact on the energy balance of the building. It was observed that a higher WWR ratio had a detrimental effect on cooling and internal temperatures, with better performance achieved by reducing WWR ratios. The most significant improvement, however, was observed while replacing the base case ceiling components with a hypothetical insulated ceiling. This yielded a substantial 38% improvement compared to the base case. Furthermore, the results clearly established a performance hierarchy among the wall assemblies, with the thermal mass wall (TM) outperforming the insulated clay brick wall (INC), which in turn outperformed the base case wall (BCT). This progression confirms that lower U-values consistently lead to better thermal performance, particularly in reducing cooling loads. The thermal mass wall had a U-value similar to the minimum limit set by SBC 602, yet it was significantly outperformed by the insulated wall assembly. This indicates that the current U-value requirements in SBC 602 are too lenient and could be revised to achieve more meaningful energy savings. By adopting stricter thermal performance standards, substantial improvements in building efficiency and occupant comfort can be realized, especially in the context of rising temperatures across the region.

While engineered solutions can effectively cool down spaces, it is imperative that buildings are designed with a focus on naturally reducing heat rather than addressing it as an afterthought. To address this aspect, an additional two studies were conducted, one focused on shading and the other on ventilation. The addition of shading led to a reduction in internal temperatures of up to 1 °C. Once again, it was noted that lower WWR ratios performed better. However, it is worth mentioning that the impact of shading on lower ratios was somewhat minor, and the overall decrease was not as significant as anticipated, possibly due to the high altitude of the sun in the region. Wind towers were thoroughly evaluated across several design variables. The inclusion of internal partitions significantly improved their effectiveness, and smaller apertures enhanced energy efficiency without compromising passive cooling performance. While taller wind towers performed better than shorter ones, the gains were modest. Further research is needed to refine the wind-tower concept, including assessing the embodied energy and overall carbon impact over the structure’s lifetime. While the paper extensively investigates building fabric, especially vertical elements, further research could be directed toward optimizing ceilings. For example, the addition of insulation demonstrated significant reductions in cooling loads, with the potential for further improvements through advanced construction techniques.

In conclusion, while individual elements performed well alone, the study assessed their collective impact, revealing a significant improvement in energy efficiency. This led to a notable 68.4% improvement compared to the base case, with favourable performance when projected into 2080, despite an expected 4 °C temperature rise. While the proposed design did not achieve year-round passive performance, it successfully maintained comfortable interior temperatures for approximately half the year. This highlights the inefficiency of conventional building practices.