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Article

Evaluation and Improvement of Daylighting Performance with the Use of Light Shelves in Mosque Prayer Halls with a Dome Structure: A Comparative Study of Four Cases in Saudi Arabia

by
Mohammed Alkhater
1,*,
Muna Alsukkar
2 and
Yuehong Su
3
1
Department of Building Engineering, College of Architecture and Planning, Imam Abdulrahman bin Faisal University, Dammam 31451, Saudi Arabia
2
Department of Architectural Engineering, Faculty of Engineering, The Hashemite University, Zarqa 13133, Jordan
3
Department of Architecture and Built Environment, University of Nottingham, Nottingham NG7 2RD, UK
*
Author to whom correspondence should be addressed.
Buildings 2025, 15(16), 2826; https://doi.org/10.3390/buildings15162826
Submission received: 27 June 2025 / Revised: 2 August 2025 / Accepted: 5 August 2025 / Published: 8 August 2025
(This article belongs to the Section Building Energy, Physics, Environment, and Systems)
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Abstract

Daylighting plays a pivotal role in mosques, shaping their sacred atmosphere and enhancing the spiritual experience for worshippers. Beyond a mere architectural consideration, the integration of natural light into mosque design fundamentally influences the ambiance and functionality of these religious spaces. This study investigates the key factors that enhance daylight levels and visual comfort within prayer halls. It specifically evaluates illuminance levels, light distribution, and glare in four domed mosques located in Saudi Arabia. Field measurements were conducted beneath the domes of these prayer spaces, each featuring clerestory windows of varying forms and dimensions. Based on architectural specifications and material properties, daylight simulations and modeling were performed using the RADIANCE engine integrated with Grasshopper. The simulation results were validated against on-site illuminance measurements to ensure model accuracy and reliability. The primary objective was to assess whether the existing daylighting conditions comply with the recommended illuminance standards for reading and prayer, typically ranging from 150 to 500 lux. This study revealed that the illuminance levels in the central dome area exceeded the recommended values, reaching over 3000 lux. To improve daylight distribution, shading systems such as flat and curved shelves were added to the drum’s windows. This research concludes that the light shelves and vacuum double glazing significantly improved indoor daylight performance by preventing direct sunlight entry into the prayer hall and redirecting it towards the dome. This intervention successfully reduced excessive illuminance levels to a more optimal level of around 447–774 lux during the noon prayer period, ensuring a balanced and comfortable environment for worshippers.

1. Introduction

The design of mosque buildings often incorporates dome structures with encircling windows on the drum, allowing continuous sunlight to illuminate the prayer hall. While this design enhances the spiritual atmosphere, it poses challenges in hot climates like Saudi Arabia, where excessive solar heat gain can lead to higher cooling demands and increased energy consumption [1]. To mitigate this issue, energy-efficient glazing solutions—such as double-glazed and tinted windows—have been adopted in contemporary mosque buildings [2,3]. Although these systems effectively reduce heat transfer [4], they often compromise the quality and uniformity of daylight distribution [5]. Direct sunlight penetration through these windows can create areas of excessive brightness and deep shadow, leading to visual discomfort within the prayer space. To address these limitations, researchers have explored advanced daylighting strategies [6]. One promising solution is the use of light shelves—horizontal elements installed above eye level to reflect daylight deeper into the interior while diffusing it to reduce glare.
These systems have proven effective in channeling and redirecting sunlight towards the ceiling while dispersing it more evenly, thereby enhancing visual comfort and the overall quality of daylighting [7,8]. Integrating light-redirecting components into the clerestory windows can enhance vertical light penetration and improve overall illuminance, especially within the first few meters from the windows [9]. Moreover, studies have shown that optimized daylighting through light shelves can significantly reduce reliance on artificial lighting, thereby lowering energy consumption [10,11] and mitigating visual discomfort [12]. For instance, light shelf systems have been reported to increase the benefit of daylight by up to 17.5% [13] and reduce visual discomfort by nearly 90%, while achieving energy savings of up to 29% [14].
In parallel, advanced glazing technologies, including vacuum glazing, low-emissivity coatings, and photovoltaic (PV) glazing—have been developed to improve both daylight control and thermal performance [15,16]. Some smart glazing systems dynamically respond to external lighting conditions, offering adaptive solutions that enhance visual comfort and energy efficiency throughout the day.

1.1. Historical Development of Daylighting Control in Dome Buildings

The integration of clerestory windows beneath domes has historically served as a fundamental daylighting strategy, particularly within religious buildings, where it exemplifies early approaches to passive lighting design [17]. This technique is prominently illustrated in the architectural composition of Hagia Sophia. Scholars such as Gervase Mathew and Thomas Whittemore have highlighted the purposeful interaction between the dome’s curved geometry and the reflective surfaces conceived by Anthemius. These elements work in concert to capture and redistribute natural light, creating a diffused, luminous environment beneath the dome [18,19]. The use of dual reflectors enhances this effect, producing a transcendent visual experience that reinforces the symbolic elevation of the sacred space above the earthly domain.
A comparable approach is evident in the dome of the Megistis Lavra Monastery, where an advanced daylighting control method was employed to modulate solar penetration. This involved widening the clerestory window openings inwardly while subtly angling the windowsills outward, directing sunlight upward toward the dome’s apex. Moreover, the strategic placement and orientation of reflective surfaces were designed to maximize light admission from the greatest number of windows at any given moment, thereby optimizing interior illumination, as seen in Figure 1.

1.2. Previous Studies on Daylighting Performance in Mosques

Extensive research has investigated daylighting strategies in mosque buildings, with particular attention given to the role of domes in modulating interior illumination. Domes, often paired with clerestory or drum windows, not only improve daylight distribution but also contribute to acoustic quality and thermal comfort by mitigating excessive solar heat gain [20,21]. Additionally, studies highlight the psychological and behavioral effects of lighting on worshippers, reinforcing the significance of well-designed daylighting systems in sacred spaces [22,23]. Hassan and Arab [24] performed a simulation-based analysis comparing two mosque roof designs—a pendentive dome and a pyramidal structure—in Mostar, Bosnia. Employing 3DStudio Max with EnergyPlus, their results demonstrated that the pendentive dome achieved more uniform illuminance levels, thereby optimizing natural light diffusion in the prayer hall. Similarly, Aljofi [25] assessed the effectiveness of domes in daylight distribution within mosques in Alkhobar. Through field surveys and experimental testing of different opening configurations, the study identified disparities in lighting uniformity, suggesting the necessity for adaptive control mechanisms to enhance illumination balance in worship areas. Further insights were provided by Ali and Mustafa [26], who examined the relationship between mosque morphology and daylight performance using metrics such as daylight autonomy and glare index. Their findings revealed that courtyards and strategically positioned vertical windows significantly improved visual comfort, underscoring the impact of architectural form on daylighting quality.

1.3. Research Problem

Mosques require well-balanced natural lighting to ensure visual comfort, functionality, and energy efficiency. While dome structures and clerestory windows are traditional architectural features that facilitate daylight entry, they often create challenges in controlling daylight levels and distribution. Specifically, excessive daylight under domes can result in glare and uneven illumination, compromising the visual comfort of worshippers and forcing them to fully block the windows, which leads to increased reliance on artificial lighting. Conversely, inadequate daylight in the peripheral areas of prayer halls can result in dim zones unsuitable for reading and praying. Despite the prevalence of these challenges, limited studies have evaluated daylight performance within domed mosque buildings using empirical field data and simulation-based validation. Therefore, a quantitative evaluation of daylighting effectiveness in large domed prayer halls is essential to enhance building performance and inform future design strategies.

1.4. Research Objective

The objective of this research is to evaluate and enhance daylighting performance in four selected mosques, which were used as case studies. To reach this objective, first, field measurements of daylight illuminance on specific days in September were conducted. Following this, the prayer halls of the mosques were then modeled using Grasshopper based on Rhinoceros, as shown in Figure 2. The simulation models were calibrated and validated against the field measurements to ensure accuracy. Ultimately, the implementation of light shelves (both flat and curved) was suggested to test their influence on enhancing daylighting performance on 21 September, 21 June, and 21 December during the noon prayer period.

2. Methodology

This study employs a mixed-method approach that integrates on-site measurements, digital simulations, and comparative analysis to assess the daylighting performance of mosque prayer halls with domed roofs. The primary objective is to assess the accuracy and reliability of the RADIANCE simulation plugin for Grasshopper by comparing its outputs with actual daylight levels recorded during field measurements. This validation step is crucial to ensuring that any subsequent daylighting improvement strategies are grounded in reliable data and reflect real-world lighting conditions.

2.1. Description of Case Studies

A comprehensive field survey was carried out across 24 mosques located in the Eastern Province of Saudi Arabia. The findings highlighted a high degree of architectural uniformity, with most mosques featuring a prominent domed structure emblematic of traditional Islamic design in the region. Due to limited time and resources, four domed mosques were selected from this larger sample for detailed daylighting analysis. These mosques were chosen not only for their accessibility but also for their representation of diverse architectural features and typical regional designs, allowing meaningful comparison and cautious generalization of findings to similar mosque configurations across the region.
Each selected mosque includes a central prayer hall topped with a dome and surrounded by clerestory or upper-level windows intended to facilitate daylight penetration. These prayer halls also share consistent architectural characteristics, such as a square layout and orientation toward the Qiblah, indicative of a unified regional design approach. The four case study mosques, presented in Figure 3, are as follows: A: Alotaibi Grand Mosque; B: Masjid Ibrahim Al-Ajami; C: Jaama Saad Bin Maaz; and D: Al Hada Mosque.

2.2. Field Measurements

Field measurements were conducted in the four selected case study mosques to evaluate the daylight levels within the prayer halls. These measurements focused on the central areas of the prayer halls, specifically the space beneath the domes. A section measuring 13 m × 13 m was chosen to evaluate the daylight performance of the top windows. Hourly illuminance value measurements were taken on a grid with a spacing of 2.0 m × 2.0 m divided into 36 squares of equal dimensions, as shown in Figure 4, positioned at a reading level of 0.35 m above the ground (at the Quran stand level) [27]. Except for the horizontal and vertical axes, they were taken on a grid with a spacing of 1.0 m × 1.0 m. The levels of illumination were then measured at the center of each square using the lux meter. The measurements campaign was limited to four days (one day for each case), from 19 to 22 September, and measurements were conducted three times a day during the noon prayer period at 10:30, 12:00, and 13:30. Daylight was measured under a clear and sunny sky, and electric lights were turned off during the measurements.

2.3. Illuminance Simulation

The results of the RADIANCE version 5.4a simulation were compared with the field measurements during the same period of 10:30–13:30 on 21 September to validate the simulation model. The validated simulation models were then used to assess the daylight performance of the proposed shading devices on 21 September, 21 June, and 21 December. Rhinoceros 3D was utilized to model the four chosen case study mosques considering the design and material characteristics of existing mosque buildings. The RADIANCE engine [28] in Grasshopper is employed to assess the daylight performance of shading devices operated through the “Honeybee and Ladybug” environmental software plugins for Grasshopper [29]. The analysis plane was set up at 0.35 m above the floor, with a 13 m × 13 m grid size to match the measurement setup. Adjacent test points were 0.50 m apart in the simulation. The estimated reflectance values of various elements such as walls, dome ceiling, and the light transmittance of windows for the simulation models are detailed in Figure 5 [30,31,32]. Weather file data sets (EPW) were used for the location of the city of Dammam (Eastern Province) in Saudi Arabia.

2.4. Daylight Metric

Useful daylight illuminance (UDI) is a widely used measure for dynamically evaluating the availability of daylight [33]. The introduction of this concept occurred in 2005 by Mardaljevic and Nabil [34]. This measure classifies daylight levels into three categories to assess their utility: adequate daylight, inadequate daylight, and excessive daylight. A previous study by Holmes [35] suggests that the optimal illumination level in prayer halls is 150 lux for praying purposes and 500 lux for reading the Quran. Based on these considerations, the UDI metric (150–500 lux), which represents the illuminance level of reading and praying requirements, was used as the evaluation and optimization metric for the daylighting objective in this study.
In addition, for the purpose of assessing the quality of visual comfort, the discomfort glare probability (DGP) is used as the metric in this study. The concept of DGP was initially introduced in 2005 [36] and validated in 2006 [37]. According to several studies [38,39] on human visual comfort, glare is unlikely to disturb occupants if the DGP level is lower than 0.35.

3. Comparison and Validation

The measurements and simulations were conducted in the selected four mosques’ prayer halls during the noon prayer time, specifically from 21 to 24 September, between 10:30 and 13:30. This time frame was chosen to correspond to the equinox’s solar availability during the year, ensuring consistent solar conditions for the measurements. A comparative analysis was performed between field measurements and the simulation modeling outputs generated in Grasshopper to verify their accuracy. The primary objective of this study was to conduct a comparison between the illuminance levels measured in the real world and the corresponding test points incorporated in the simulation model.
The analysis showed that there was significant variation in the average distribution of daylight illuminance levels within the prayer halls on an hourly basis, as shown in Figure 6. In the first scenario (Case B), the dome openings allowed for high levels of direct sunlight, ranging from 1438 to 2962 lux. However, these levels significantly decreased towards the lower sections of the windows, reaching as low as 220 lux and 303 lux. Thus, the daylight coverage during the noon prayer time did not exceed 38% of the recommended range of 150–500 lux.
On the other hand, in Cases A and C, more than 61% of the average illuminance in the prayer halls exceeded the recommended level. The maximum values recorded were 2240 lux and 1822 lux in both case studies, respectively, which are considered relatively high. However, in Case D, the measured illuminance levels were notably insufficient, with all data points falling below the minimum requirement. The highest recorded illuminance level in this case was only 139 lux, which is considered significantly low.

4. Daylighting Improvement Approach

An analysis from the previous section of this study revealed that the current utilization of glazing imposes limits on achieving the desired levels of daylighting in prayer halls. In Cases A, B, and C, excessive illuminance levels under the domes were observed during noon prayer time. Conversely, in Case D, insufficient levels of lighting were observed due to the low transmittance of the glass and the inadequately designed shading devices. Consequently, it is imperative to investigate replacing the existing glass with a higher-performing alternative.
The improvement approach incorporated the implementation of vacuum double glazing, which shows outstanding characteristics in improving light transmission, superior heat insulation, and thermal efficiency, as indicated in Table 1. Furthermore, informed by prior research on shading device effectiveness, two types of external aluminum light shelves—flat and curved, each with a reflectivity of 75%—were proposed to improve daylight distribution, as illustrated in Figure 7. These devices are designed to redirect incoming sunlight toward the dome ceiling, which then diffuses the light through its curved surface and distributes it more evenly within the prayer space. Both types of light shelves were evaluated in a horizontal configuration (0° tilt), with their depth calculated using Equation (1) [40]:
Light   shelf   depth   =   X tan VSA
where VSA is the vertical shadow angle, and X is a louver spacing.

5. Daylighting Improvement Results

The main objective of this phase is to use the base cases for prayer halls and improve their daylighting performance with the aim of achieving an acceptable range of useful daylight illuminance between 150 and 500 lux for user visual comfort.
The improvement method utilized the same RADIANCE materials and specifications as in the cases analyzed using the validation approach (as described in Section 2.3). This allowed us to conduct a comparative analysis of the performance of the daylight redirecting systems in the same prayer halls under consistent conditions, including weather data and grid settings, at three typical times: 21 June, 21 September, and 21 December during the noon prayer time.

5.1. Comparison Study Findings for 21 September at the Noon Prayer Time

The results from Figure 8 and Figure 9 show that incorporating light shelves achieved a notable enhancement in the daylight coverage percentage in the four selected case studies. The addition of flat shelves resulted in average coverage percentages of 72%, 79%, 58%, and 84% for Cases A, B, C, and D, respectively. Similarly, the curved shelves achieved average coverage percentages of 76%, 80%, 59%, and 81%, respectively, for the same cases. In comparison, the base scenario without any shelves achieved lower coverage percentages of 54%, 70%, 40%, and 15%, respectively.
In terms of glare evaluation, the amount of glare in Case B remained consistent across all scenarios, ranging from 0.25 to 0.23. However, in Cases A, C, and D, the introduction of proposed shadings resulted in slightly higher levels of glare compared to the unshaded scenario, with increases of 3%, 6%, and 17%, respectively. These increases can be attributed to the second reflection from the bottom of the light shelves.
On the other hand, the cross-sections in Figure 10 illustrate the different levels of daylight illuminance observed in the prayer halls. The implementation of light shelves had an important impact on decreasing the high levels of average illuminance observed in the base cases (A, B, and C). In the absence of light shelves, the intense solar radiation resulted in measured illuminance levels of 1551 lux, 3202 lux, and 1391 lux under the domes for Cases A, B, and C, respectively. However, upon introducing flat and curved shelves in these cases, a noticeable reduction in illuminance levels was observed. Specifically, the measured illuminance values decreased to 784–753 lux, 782–697 lux, and 753–695 lux, respectively, which are almost approaching the maximum value of the acceptable range of illumination levels of 500 lux.
In Case D, the improvement process resulted in notable enhancements in illuminance levels. It expanded the range from 77 lux to 183 lux in the base scenario, reaching a range of 198 lux to 585 lux in the flat shelf scenario. Additionally, during the curved shelf scenario, the improvement led to a range of 214 lux to 606 lux, further augmenting the illuminance levels.

5.2. Comparison Study Findings for 21 June and 21 December at the Noon Prayer Time

On 21 June, as shown in Figure 11 and Figure 12, at 12:00, the implementation of light shelves played a significant role in mitigating the impact of intense solar radiation, thereby minimizing excessive lighting. These light shelves have improved the percentage of useful daylight coverage in Cases A, B, and C, ranging from 5% to 10%. Notably, in Case D, the improvement increased from 39% to 77% of the coverage for the daylight illuminance range of 150~500 lux, due to the reduced exposure to intense solar radiation resulting from the smaller window size. While the proposed light shelves have demonstrated their effectiveness in mitigating the impact of intense solar radiation during periods of high solar radiation, notable improvements in the percentage of useful daylight coverage area have also been observed at 10:30 and 13:00. Specifically, in Cases A, B, and D, the percentage of useful daylight coverage has increased by 71%, 75%, and 83%, respectively. With a slight preference for curved shelves, an average increase of up to 7% has been observed. This is due to the curved shape’s distribution effect, which diffuses the received light more frequently than the flat shape’s tendency to reflect the same amount of the received light. However, in Case C, the performance of the shelves was affected by the larger windows size, as the percentage of useful daylight coverage did not exceed 48%.
On 21 December, as shown in Figure 13 and Figure 14, the performance of the light shelves in Cases A, B, and D is almost similar during the noon prayer time. The useful illuminance coverage percentage ranges from 69% to 84%, which is considered satisfactory for ensuring visual comfort for worshippers in prayer halls. Furthermore, when evaluating glare, the daylight glare probability (DGP) results for both the base cases without shading and the suggested shading solutions are below 0.3 on most dates and times. However, on 21 June, 21 December (at three specific times), and 21 September, both light shelves generate slightly more glare (at 3% and 19%) compared to the base cases without any shading. The reason for this is that the amount of light reflected off the surface of the shelf can contribute to an increase in brightness levels. This issue will be addressed in a future study by implementing advanced shading systems.

6. Discussion

This study aimed to enhance daylighting performance within four domed mosque prayer halls located in hot climatic regions. A comprehensive validation process was conducted, combining daylighting simulation with on-site illuminance measurements to assess daylight levels and distribution. The goal was to identify optimal daylighting performance in prayer halls by employing a simulation model with an exterior light shelf (flat and curved).
-
Evaluation
The analysis revealed a significant disparity in the distribution of daylight across the prayer halls. Specifically, the central zone directly beneath the dome receives intense levels of daylight, often resulting in excessive brightness and direct sunlight. This over-illumination can cause visual discomfort and glare, necessitating the use of shading devices or complete window closures to reduce its impact. In contrast, as one moves away from the center of the dome toward the periphery of the prayer hall, daylight levels gradually decrease, eventually approaching the minimum illumination levels recommended for visually performing prayers.
These findings highlight a critical imbalance in daylight distribution caused by the current window configuration. While the dome-side clerestory windows provide abundant daylight to the central zone, they fail to adequately illuminate peripheral areas of the prayer hall. This uneven daylighting pattern not only compromises visual comfort but also increases reliance on artificial lighting in underlit zones, thereby affecting both energy efficiency and user experience.
-
Validation
In the validation process, the average illuminance was calculated for each prayer hall. Consequently, the average error for illuminance levels is calculated by comparing the simulated illuminance values with the actual or measured illuminance values in each case. The results showed that the average error for illuminance levels in the four selected cases were as follows: A: 16.6%; B: 5.9%; C: 11.8%; and D: 20.4%. In Case D, one of the key challenges encountered in this study was the inability to directly assess the physical condition of the upper clerestory windows surrounding the central dome. These windows are sealed and composed of two glazing layers (double façade window system), and they have accumulated a significant amount of dust and debris over time. Due to their inaccessibility, it was not possible to accurately evaluate the degree of cleanliness, light transmittance, or the current state of the glazing material. This limitation may have contributed to the observed discrepancies between the measured daylight levels and the simulated results. The simulation assumed ideal or nominal transmittance values for the glazing, which may not reflect the actual conditions, thereby influencing the accuracy of the comparison. However, these error values fell within an acceptable range based on previous studies, which considered simulation errors ranging from 20 to 30% [42,43]. Therefore, this margin of error is considered acceptable and will be utilized for further analysis.
-
Improvement
The implementation of light shelves highlighted their effectiveness in improving lighting performance across all four case studies. At all times, there are no light patches on the prayer hall plane when light shelves are applied. By efficiently blocking and reflecting sunlight towards the dome ceiling, they successfully reduced the intensity of solar radiation. Additionally, the curved ceiling of the dome played a vital role in distributing and diffusing the reflected sunlight in the prayer halls.

7. Conclusions

In conclusion, this study has demonstrated the significance of daylighting strategies in mosques, specifically in prayer halls with dome structures. The research focused on evaluating and analyzing the indoor daylight quality of four selected existing mosques on 21 September during the noon prayer period. The results of the field measurements were then compared with the RADIANCE simulation results during the same period of 10:30–13:30 on 21 September to validate the simulation model. The findings revealed that the existing illuminance levels under the domes exceeded the recommended values, leading to discomfort and glare for worshippers.
To address this issue, this study implemented shading systems in the form of flat and curved shelves on three typical days: 21 June, 21 September, and 21 December during the noon prayer time. By utilizing proposed elements of shading and glazing through simulation and modeling tools, such as Grasshopper, a parametric software plugin based on Rhinoceros 3D, the daylighting quality was analyzed using Honeybee and Ladybug plugins as engines for RADIANCE. The results of the improvement showed that the application of light shelves significantly improved the indoor daylighting performance in the prayer halls. The average coverage percentages of useful daylight illuminance between 150 and 500 lux increased, with the average reaching up to 73%, 59%, and 70% using the flat shelves scenario and 74%, 61%, and 71% for using the curved shelves scenario on 21 September, 21 June, and 21 December, respectively. These improvements ensured a more balanced and visually comfortable environment for worshippers.
Although there was a slight increase in glare in some cases after the improvement, the overall advantages of enhanced daylight distribution exceeded this issue. The implementation of light shelves successfully reduced the intensity of solar radiation and controlled the illuminance levels. The curved ceiling of the dome also played a crucial role in distributing and diffusing the reflected sunlight. As a result, the proposed approach has significant potential for reducing electrical lighting energy consumption and achieving energy savings in mosque buildings, along with potential cooling energy savings. Therefore, future research in this area could investigate the integration of energy-efficient lighting technologies, such as LED lighting or smart lighting controls, in conjunction with the proposed systems to assess how these technologies can further enhance energy savings and improve lighting quality. Additionally, field measurements in this study were limited to midday during a short research visit from the UK. Future studies should conduct extended measurements across different times of day and seasons to capture dynamic daylighting conditions and improve the reliability and accuracy of simulation validation.
In conclusion, this study highlights the importance of improving indoor daylight quality in the prayer halls of mosques with dome structures. The implementation of advanced glazing systems and utilization of aluminum exterior light shelves proved to be effective in improving the distribution of daylight and reducing excessive illuminance levels.

Author Contributions

Methodology, M.A. (Mohammed Alkhater), M.A. (Muna Alsukkar) and Y.S.; Software, M.A. (Mohammed Alkhater) and M.A. (Muna Alsukkar); Validation, M.A. (Mohammed Alkhater); Formal analysis, M.A. (Mohammed Alkhater) and M.A. (Muna Alsukkar); Investigation, M.A. (Mohammed Alkhater), M.A. (Muna Alsukkar) and Y.S.; Resources, M.A. (Mohammed Alkhater); Writing—original draft, M.A. (Mohammed Alkhater); Writing—review & editing, M.A. (Muna Alsukkar) and Y.S.; Supervision, Y.S.; Project administration, M.A. (Mohammed Alkhater). All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Illustration of the path of reflected light, traced from Anthemius’ reflectors toward the dome and the sloped surface of the windowsill [18].
Figure 1. Illustration of the path of reflected light, traced from Anthemius’ reflectors toward the dome and the sloped surface of the windowsill [18].
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Figure 2. The four case studies of mosques for daylighting measurement.
Figure 2. The four case studies of mosques for daylighting measurement.
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Figure 3. Elevations, daylighting strategies, and architectural elements of the four case study mosques.
Figure 3. Elevations, daylighting strategies, and architectural elements of the four case study mosques.
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Figure 4. Interior view of the test prayer hall (left); grid of measurement points (right).
Figure 4. Interior view of the test prayer hall (left); grid of measurement points (right).
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Figure 5. A perspective view of the base model configuration in a virtual prayer hall.
Figure 5. A perspective view of the base model configuration in a virtual prayer hall.
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Figure 6. The cross-sectional view of the comparison between measured and simulated illuminance levels for four cases during the noon prayer time on 21 September: (A): Case A; (B): Case B; (C): Case C; and (D): Case D.
Figure 6. The cross-sectional view of the comparison between measured and simulated illuminance levels for four cases during the noon prayer time on 21 September: (A): Case A; (B): Case B; (C): Case C; and (D): Case D.
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Figure 7. The proposed scenarios of light shelves (flat and curve) for daylighting improvement.
Figure 7. The proposed scenarios of light shelves (flat and curve) for daylighting improvement.
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Figure 8. A comparison of daylight glare probability and illumination maps for base scenario and two light shelf design (curved and flat) scenarios for Case A on 21 September.
Figure 8. A comparison of daylight glare probability and illumination maps for base scenario and two light shelf design (curved and flat) scenarios for Case A on 21 September.
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Figure 9. A comparison of coverage percentage for the daylight illuminance range of 150–500 lux and daylight glare probability during noon prayer times on 21 September for all case studies.
Figure 9. A comparison of coverage percentage for the daylight illuminance range of 150–500 lux and daylight glare probability during noon prayer times on 21 September for all case studies.
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Figure 10. The cross-section view of a comparison of the illuminance levels of the base scenario and improved scenarios (flat and curved) on 21 September for all case studies: (A): Case A; (B): Case B; (C): Case C; and (D): Case D.
Figure 10. The cross-section view of a comparison of the illuminance levels of the base scenario and improved scenarios (flat and curved) on 21 September for all case studies: (A): Case A; (B): Case B; (C): Case C; and (D): Case D.
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Figure 11. A comparison of daylight glare probability and illumination maps for the base scenario and two light shelf design (curved and flat) scenarios for Case A on 21 June.
Figure 11. A comparison of daylight glare probability and illumination maps for the base scenario and two light shelf design (curved and flat) scenarios for Case A on 21 June.
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Figure 12. A comparison of coverage percentage for the daylight illuminance range of 150–500 lux and daylight glare probability during noon prayer times on 21 June for all case studies.
Figure 12. A comparison of coverage percentage for the daylight illuminance range of 150–500 lux and daylight glare probability during noon prayer times on 21 June for all case studies.
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Figure 13. A comparison of daylight glare probability and illumination maps for base scenario and two light shelf design (curved and flat) scenarios for Case A on 21 December.
Figure 13. A comparison of daylight glare probability and illumination maps for base scenario and two light shelf design (curved and flat) scenarios for Case A on 21 December.
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Figure 14. A comparison of coverage percentage for the daylight illuminance range of 150–500 lux and daylight glare probability during noon prayer times on 21 December for all case studies.
Figure 14. A comparison of coverage percentage for the daylight illuminance range of 150–500 lux and daylight glare probability during noon prayer times on 21 December for all case studies.
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Table 1. Vacuum double glazing window specifications [41].
Table 1. Vacuum double glazing window specifications [41].
NameThickness (mm)U-ValueG-ValueVisible Transmittance
Vacuum double glazing9.21.40.610.73
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MDPI and ACS Style

Alkhater, M.; Alsukkar, M.; Su, Y. Evaluation and Improvement of Daylighting Performance with the Use of Light Shelves in Mosque Prayer Halls with a Dome Structure: A Comparative Study of Four Cases in Saudi Arabia. Buildings 2025, 15, 2826. https://doi.org/10.3390/buildings15162826

AMA Style

Alkhater M, Alsukkar M, Su Y. Evaluation and Improvement of Daylighting Performance with the Use of Light Shelves in Mosque Prayer Halls with a Dome Structure: A Comparative Study of Four Cases in Saudi Arabia. Buildings. 2025; 15(16):2826. https://doi.org/10.3390/buildings15162826

Chicago/Turabian Style

Alkhater, Mohammed, Muna Alsukkar, and Yuehong Su. 2025. "Evaluation and Improvement of Daylighting Performance with the Use of Light Shelves in Mosque Prayer Halls with a Dome Structure: A Comparative Study of Four Cases in Saudi Arabia" Buildings 15, no. 16: 2826. https://doi.org/10.3390/buildings15162826

APA Style

Alkhater, M., Alsukkar, M., & Su, Y. (2025). Evaluation and Improvement of Daylighting Performance with the Use of Light Shelves in Mosque Prayer Halls with a Dome Structure: A Comparative Study of Four Cases in Saudi Arabia. Buildings, 15(16), 2826. https://doi.org/10.3390/buildings15162826

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