A Proposal for the Improvement of Daylight Integration and Distribution in the Educational Interior Space Through a (Pro-Sun) Ceiling Design with Curved Surfaces

Abstract

The use of daylight as the primary lighting source in buildings is crucial for achieving energy savings. Significantly reducing the dependence on artificial lighting sources relies on more efficient utilization of available daylight and enhancement of its quantity and distribution within interior spaces. The appropriate use of daylight not only enhances energy efficiency in indoor spaces but also positively impacts users’ health and performance. A growing body of research has focused on methods for maximizing the use of daylight in interior environments. This study proposes a ceiling design aimed at utilizing daylight more efficiently in interior spaces. The quantity of daylight in an educational space was calculated using the VELUX Daylight Visualizer program by comparing the results of existing, diagonal, and curved ceiling designs. Light levels were measured before and after the addition of Pro-Sun to assess daylight integration and distribution in the studios’ interior spaces. The design studio was analyzed based on orientation (north-south), school semester, active hours, and ceiling type. As a result of the comparison of ceiling types, the Pro-Sun ceiling system with curved reflectors had the most daylight integration capacity and distribution in the deeper the studio’s interior space.

1. Introduction

In recent decades, growing concerns regarding energy consumption and environmental sustainability have significantly enhanced the energy efficiency and quality of interior lighting in building designs. Despite advancements in lighting technology, achieving the same quality and intensity of illumination as natural daylight remains elusive [1]. Studies have suggested that lighting control systems can reduce electricity consumption by 20%, with reductions reaching 60% under optimal conditions [2]. Türkiye has a significant solar energy potential due to its geographical location. According to the Türkiye Solar Energy Potential Atlas (GEPA) prepared by Ministry of Energy and Natural Resources, the average annual total sunshine duration is 2741 h and the average annual total radiation value is calculated as 1527.46 kWh/m² [3]. The EU Green Light Program [4], developed and implemented by the European Union, and the Canadian Green Building Council [5], administered nationally by the Canadian government, represent two of the most contemporary and notable examples of energy-efficiency initiatives. In response to growing environmental challenges, the European Commission launched the Circular Economy Action Plan in 2020 as a strategic framework to address the unsustainable exploitation of natural resources. This initiative seeks to reduce the environmental burden by promoting resource efficiency and waste minimization throughout the lifecycle of products. By fostering a shift from a linear to a circular economy model, the plan aims to enhance sustainability, stimulate innovation, and contribute to the European Union’s broader goals of climate neutrality and economic resilience [6]. The decisions made by designers during the design phase and the subsequent enhancements derived from these decisions are primarily intended to optimize the user’s visual comfort and save energy. Daylight is admitted to interior spaces by establishing a seamless connection with the exterior through strategically placed openings and transparent surfaces within a building’s lighting shell. Daylight guidance systems facilitate the distribution of adequate natural light within interior spaces, contributing to the establishment of optimal visual comfort conditions. These systems enhance user perception of sufficient illumination within a space, thereby reducing their reliance on artificial lighting sources. The primary goal was to minimize the energy required for lighting by efficiently harnessing daylight. In addition to satisfying interior lighting requirements, daylight guidance systems aim to extend daylight deeper into the spaces. A key factor in significantly reducing the reliance on electric lighting is the effective utilization of available daylight, which can be enhanced by increasing its distribution and intensity.

The area benefiting most is called a daylight or perimeter area and is affected mainly by window placement and dimensions. Consequently, daylight distribution is not uniform in deep spaces, even when a fully glazed facade is used. In these cases, daylight alone cannot adequately illuminate the space without additional support from artificial lighting, especially in areas away from the façade [7]. Improving daylight depth and efficiency in interior spaces is an important spatial design solution. By collecting most of the energy and light, the ceiling design primarily maximizes daylight penetration into the interior space. Numerous spatial strategies have been devised to optimize the relationship between ceiling structures and daylight systems, thereby significantly enhancing the quality and distribution of natural light within buildings. Considering the positive impact of daylight on people, it is advisable to design facades with glass from the workplace level to the ceiling. In flexible interior spaces such as classrooms in educational buildings, it is essential to position luminaries parallel to windows to ensure optimal working conditions (Figure 1).

Daylight is a crucial factor influencing human psychology and physiology, as it impacts our circadian rhythms and general health. Moreover, prior research has highlighted the beneficial effects of daylight exposure on users’ health [9], the overall well-being of office workers [10], and on mood and sleep patterns [11]. Additionally, visual comfort plays a significant role in shaping user behavior, productivity, and overall well-being, particularly in educational settings. Furthermore, the integration of natural daylight not only reduces reliance on artificial lighting but also enhances the overall learning experience by improving visual comfort and reducing glare, which is critical in classroom settings [12].

The positive health implications associated with daylight are broad, and the energy-efficient strategy of maximising natural light is now routinely used to aid in the lighting, heating, and cooling of buildings [13]. For instance, the incorporation of daylight into classrooms is crucial for students who spend much of their time in school as it positively affects both mental activity and psychological well-being. In the learning environment, daylight plays a significant role in creating a better environment for teaching and learning, as poorly lit classrooms negatively affect students’ health and learning ability [14]. One study found that students in classrooms with abundant daylight performed math 20% faster and reading 26% faster in reading [15]. Another extensive study revealed that students in classrooms with natural light from both ceiling and windows achieved 19% better reading scores and were 20% more successful on standardized tests than those in less-lit classrooms [16]. Daylight is widely recognized as a key factor that influences the quality of learning in educational spaces. Various studies have investigated the ideal balance between space and daylight, such as using light shelves and louvers on windows to reflect light from the ceiling. Natural light enters school buildings through elements such as windows, skylights, louvers, and light shelves, and the amount of daylight can be increased using adjustable panels [17,18,19].

The studies conducted within the scope of the literature primarily focus on bringing daylight into the interior through a light shelf designed either outside or within the window of the building’s facade. Freewan et al. not only addressed a light shelf designed on the facade but also considered the ceiling design of the interior space. However, in this study, the existing ceiling was considered in various forms and included in the measurement [20].

The design of ceilings in educational buildings plays a pivotal role in maximizing daylight penetration while maintaining thermal comfort. Light shelves, for example, are architectural features that can redirect natural light deeper into spaces, thereby reducing the need for artificial lighting during daylight hours. Research has shown that external light shelves can significantly enhance daylight availability in classrooms, contributing to energy savings and improved occupant comfort [21,22].

This study proposes a ceiling design in which most of the light and energy is collected and distributed in the interior space. The ceiling design comprises curved surfaces. Thus, ceiling design, particularly with the use of curved forms and the integration of light shelves, is vital for improving daylight penetration and distribution in interior spaces [23]. The combination of these architectural features with advanced design tools can enhance daylight efficiency and ultimately foster more sustainable and comfortable environments.

As indicated by the findings of previous studies, a decision was made to conduct a comprehensive study focused on optimising the integration of daylight within interior spaces, approaching the issue from a more nuanced and in-depth perspective. This study examined how building orientation, geographic location, and variations in climate induced by daylight affect the effectiveness of interior lighting. In volumes featuring vertical windows, it was observed that while high levels of illumination were achieved near the windows, the intensity of light diminished progressively as one moved further away, leading to inadequate lighting in deeper areas of the space. The ceiling design proposed in this study was intended to enhance the diffusion of daylight, thereby improving its penetration into recessed areas of the interior space.

The integration of advanced daylighting design systems can substantially decrease electricity consumption while simultaneously improving the quality of interior illumination. Moreover, leveraging natural daylight provides a range of economic and ecological benefits [24]. As demonstrated in Brzezicki’s research, the integration of light shelves with different ceiling designs and curved forms, has been shown to enhance daylight uniformity and reduce glare [25]. An effective design strategy involves the use of curved ceilings. Studies have shown that these shapes significantly improve the light distribution by directing daylight more efficiently than flat ceilings. For example, Weibicycle and Matusiak highlighted that curved ceilings can notably enhance light distribution in spaces lit by passing daylight through laser-cut acrylic panels (LCPs) [26]. Similarly, Eltaweel and Su found that a curved ceiling with a 45° tilt angle can redirect light reflected from louvers and improve daylight performance in deeper room areas [27]. Freewan’s research further supports this, showing that curved ceilings can increase daylight levels in the rear sections of a room by 20% compared to flat ceilings, while also improving light uniformity [28].

To establish an engaging and esthetically pleasing lighting environment in interiors, it is essential to achieve optimal illumination levels while ensuring a uniform distribution of light [29]. A curved surface reflects light in multiple directions, depending on the point of incidence. Consequently, curved light shelves can enhance daylight performance by diffusing light when daylight is introduced into a space. This occurs because the reflections of the curved surface bring in natural light, regardless of the external environmental conditions. As shown in Figure 2, a curved surface can reflect light in various directions depending on the point of incidence. The reflection process on a curved surface can be elucidated through Figure 2, which illustrates that when light strikes a curved surface, a tangential plane is established at the point of incidence. Subsequently, a normal vector perpendicular to this tangential plane is derived [30].

The distinctive shapes of gabled and curved ceilings can more than double the amount of natural light introduced into an indoor space by a light shelf, as the light is reflected off the ceiling’s surface. This effect significantly enhances the daylight performance. The illumination performance of an external light shelf can be enhanced by increasing the slope and curvature of sloped, gabled, and curved ceilings, as noted in this study. This improvement occurs because the greater slope and curvature allow more daylight to penetrate the room. Additionally, widening and adjusting the angle of the external light shelf tends to boost its illumination effectiveness. Performance evaluation indicates that daylight capabilities improve as the curvature of the ceiling surface increases, particularly because the curvature helps diffuse natural light. Consequently, this paper proposes a ceiling system composed of consecutive linear circular surfaces. Measurement indicates that this system channels sunlight further into space than flat or diagonal ceilings.

2. Methodology

In this context, instead of focusing on applications related to the building’s exterior, this study proposes a new ceiling design aimed at enhancing the spread of daylight deeper into the interior by concentrating on the interior space. This study aims to enable daylight to reach deeper into the interior more efficiently through a curved ceiling surface. Based on the literature, two different forms of ceiling designs, diagonal (angled) and curved, were examined and compared. Measurements conducted through simulation programs indicate that curved components are more effective than diagonal forms in providing illumination by capturing and reflecting the majority of daylight throughout the interior space. Research sequence steps are explained in Figure 3.

The study proposes the following research questions:

• To what degree will Pro-Sun improve the reflection and distribution of daylight in the studio’s interior space?
• What is the difference in daylight integration between diagonal and curved ceiling designs within the studio’s interior space?

2.1. Case Study

The case was situated within the Faculty of Architecture and Design at the TOBB University of Economics and Technology campus in Ankara, Turkey. Providing detailed contextual information regarding the institutional framework is imperative for establishing robust evaluation criteria. This university, distinct from most higher education institutions in Turkey, operates on a tri-semester system (fall, spring, and summer), resulting in sustained and intensive utilization of the space across all three academic periods. Consequently, the design studio under investigation was used continuously throughout the year by students enrolled in the Department of Interior Architecture and Environmental Design from 9:30 AM to 5:00 PM. To ensure consistency and technical accuracy in evaluating the performance of various ceiling designs using the VELUX Daylight Visualizer program, the 21st day of each month was selected. This decision is based on the significance of the solstices occurring on 21 June and 21 December, which represent the longest and shortest days of the year, respectively. Solstices provide critical reference data for assessing the impact of seasonal variations on the distribution of natural light in indoor spaces. Aligning the analysis with these specific dates allows for an understanding of how ceiling designs influence light distribution during periods of maximum and minimum natural daylight. Furthermore, conducting simulations on the 21st day of other months prevents arbitrary selection and establishes a consistent reference point for light measurements throughout the year (

Table 1. Objectives and existing daylight levels of design studio, TOBB ETU.

Room Size and Material
Size	1350 cm(w) × 900(d) × 360(h)
Reflectance	Ceiling30%, Wall30%, Floor62%
Window Size and Material
	Size		Transmissivity
P1	330 cm(w) × 325(d) × 270(h)		Double-glazed 12 mm
P2	330 cm(w) × 325(d) × 270(h)		Double-glazed 12 mm
P3	270 cm(w) × 325(d) × 270(h)		Double-glazed 12 mm
Daylight
		January (21st)	February (21st)	March (21st)
	09.30	Flat (1259.4 lx)	Flat (1609.5 lx)	Flat (531.5 lx)
Spring	12.30	Flat (1260.8 lx)	Flat (1630.7 lx)	Flat (1987.5 lx)
	15.30	Flat (207.7 lx)	Flat (531.5 lx)	Flat (1956.1 lx)
		May (21st)	June (21st)	July (21st)
	09.30	Flat (819.4 lx)	Flat (1292.8 lx)	Flat (1376.4 lx)
Autumn	12.30	Flat (2496.3 lx)	Flat (2482 lx)	Flat (2436.9 lx)
	15.30	Flat (2395.8 lx)	Flat (2479.8 lx)	Flat (2420.4 lx)
		September (21st)	October (21st)	November (21st)
	09.30	Flat (1941.9 lx)	Flat (1617.9 lx)	Flat (1280.4 lx)
Summer	12.30	Flat (1845.9 lx)	Flat (1447.1 lx)	Flat (1129.7 lx)
	15.30	Flat (671.5 lx)	Flat (270.1 lx)	Flat (1.4 lx)

).

The design studio, encompassing a floor area of 117 m², contains three window apertures positioned along the northern façade of the building. The interior is furnished with workstations consisting of tables and stools optimized for drawing, drafting, and model-making, which are core activities in the pedagogical process. The flooring is finished with light grey microconcrete, and the vertical and horizontal surfaces (walls and ceiling) are uniformly coated with a matte white finish. The design studio is equipped with furniture and resources, including whiteboards, work desks, stools, and cork boards, facilitating students’ ability to display their project sheets and engage in collaborative work (Figure 4).

This research analyzes the studio interior space in terms of several key spatial and temporal factors—its north-south orientation, the academic calendar under which it is utilized, the operational hours during which it is active, and the characteristics of its ceiling structure. These aspects are critical for understanding the interior spatial dynamics and functional efficacy of studios within the broader context of interior architectural education. In this study, the ceiling design, window dimensions, classroom dimensions, and direction of light were considered the basic criteria in the evaluations made to increase the natural light performance of the classroom. Two different ceiling designs were considered—diagonal (30° inclined) and curved shapes—and the contributions of these designs to the lighting quality of the classroom were examined (Figure 5).

2.2. Simulation Setup

This study conducted a performance evaluation according to the shape of the ceiling surface of a given indoor space and used the VELUX Daylight Visualizer simulation program as a tool for analysis. Due to the inherently visual nature of such simulations, these software programs are more commonly utilized by designers compared to thermal and energy modeling software. As presented in Table 1, ceiling systems designed to increase the natural light performance of the classroom, ceiling shape (diagonal and curved), slope angle (30°), window dimensions (270 cm × 320 cm), general dimensions of the classroom (1300 cm × 900 cm), and north were evaluated within the framework of criteria such as directional light reception. The potential of each parameter to increase the amount of natural light and ensure a balanced light reaching different parts of the classroom was considered.

The environmental variables affecting natural light intake in the classroom are discussed in detail in Figure 6. During the evaluation, seasonal differences (spring, summer, and winter), northern light reception, and different times of day (09:30, 12:30, and 15:30) were determined as the main criteria. The direction of light and the amount of light changing at different times of the day were considered to analyze the performance of the designed ceiling systems.

In the analysis in Figure 7, classroom dimensions (1300 cm × 900 cm) and north-oriented window dimensions (270 cm × 320 cm) were taken into account, and in light of these data, the light-directing and -distributing performance of the ceiling designs was evaluated. Considering that north-oriented light provides ideal illumination with homogeneity, especially in classroom environments, the extent to which this light reaches the depths of the classroom was analyzed according to the ceiling shapes.

These criteria were evaluated as a whole to optimize the use of daylight in the studio and provide homogeneous illumination in all seasons, thus ensuring that design decisions are compatible with environmental conditions.

In the general approach of the study, the ability of the diagonal ceiling to direct the light coming from the north to a specific focal point and the potential of the curved ceiling to provide homogeneous illumination by spreading the light over a wider area were evaluated comparatively. The data in Table 1 were analyzed by evaluating these criteria as a whole to provide design suggestions for the maximum use of natural light and ensure a balanced light distribution in the classroom.

3. Results

A performance evaluation was conducted according to the shape of the ceiling surface of a given interior space using the VELUX Daylight Visualizer program as a tool for analysis. Photoshop 2020 was used to visualize the inflow of light. In this context, flat, diagonal, and curved ceiling types were examined.

3.1. The Existing Flat Ceiling

• Overall Performance:

• A flat ceiling receives light only at an angle that falls on its flat surface. Because this design does not direct natural light, the amount of light remains low outside midday hours effectively;
• Lux values generally remain constant at the lowest levels, depending on the season and time (Figure 8).

• Numerical Data:

• Winter Months (January): It provides 1259.4 lux in the morning (09:30), 1260.8 lux at noon (12:30), and only 207.1 lux in the evening (15:30);
• Summer Months (July): Although it performs slightly better with 2436.9 lux in the morning, 2420.4 lux at noon, and 1349.4 lux in the evening, it is still lower than diagonal and curved designs.

• Weaknesses:

• Decrease in light in the evening: For example, in January, it dropped to a low value of 207.1 lux in the evening;
• Seasonal differences: Even in summer, the performance of the flat ceiling is limited (

  Table 2. Flat ceiling daylight levels of design studio, TOBB ETU.

  Semester	Month	Ceiling Type/Light Flux (Lux)
  		Flat
  Spring	21st January
  		9.30	12.30	15.30
  	21st February
  		9.30	12.30	15.30
  	21st March
  		9.30	12.30	15.30
  Autumn	21st May
  		9.30	12.30	15.30
  	21st June
  		9.30	12.30	15.30
  	21st July
  		9.30	12.30	15.30
  Summer	21st September
  		9.30	12.30	15.30
  	21st October
  		9.30	12.30	15.30
  	21st November
  		9.30	12.30	15.30

  ).

3.2. The Ceiling with Diagonal Surfaces (30°)

• Overall Performance:

• A diagonal ceiling can receive natural light at a wider angle than an inclined structure. This provides higher lux values, particularly during midday hours. In addition, the slope adapts to the seasonal angle of sunlight, increasing its efficiency even in winter (Figure 9).

• Numerical Data:

• Winter (January).

  ○

  2607.9 lux in the morning, 3216.4 lux at noon, and 1205.6 lux in the evening;

  ∘

  provides 107% more light in the morning, 155% at noon, and 482% in the evening than a flat ceiling.

• Summer (July)

  ○

  5148.6 lux in the morning, 5831.4 lux at noon, and 3676.4 lux in the evening;

  ∘

  provides 111% more light in the morning, 141% at noon, and 172% more light in the evening than a flat ceiling.

• Advantages:

• Strong performance in winter months: Provides significant improvement, especially compared to a flat ceiling;
• Maximum performance during the middle of the day: increases the use of natural light during peak daylight hours.

• Weaknesses:

• It does not have a light-reflecting capacity as wide as a curved ceiling. In the evening hours (e.g., 3676.4 lux at 15:30 in July), it performed lower than the curved ceiling (

  Table 3. Diagonal (30°) ceiling daylight levels of design studio, TOBB ETU.

  Semester	Month	Ceiling Type/Light Flux (Lux)
  		Diagonal (30°)
  Spring	21st January
  		9.30	12.30	15.30
  	21st February
  		9.30	12.30	15.30
  	21st March
  		9.30	12.30	15.30
  Autumn	21st May
  		9.30	12.30	15.30
  	21st June
  		9.30	12.30	15.30
  	21st July
  		9.30	12.30	15.30
  Summer	21st September
  		9.30	12.30	15.30
  	21st October
  		9.30	12.30	15.30
  	21st November
  		9.30	12.30	15.30

  ).

3.3. The Ceiling with Curved Reflectors

• Overall Performance:

• A curved ceiling provides the highest light value by collecting natural light from all directions using its organic curve. It optimizes light distribution and provides efficient illumination even during the morning and evening hours (Figure 10).

Figure 10. Inflow of daylight with a curved ceiling.

Figure 10. Inflow of daylight with a curved ceiling.

• Numerical Data:

• Winter (January).

  ○

  2916.5 lux in the morning, 2929.2 lux at noon, and 1509.8 lux in the evening;

  ∘

  provides 131% more light in the morning, 132% at noon, and 629% more light in the evening than a flat ceiling;

  ∘

  provided 12% more light in the morning and 25% more light in the evening compared to the diagonal ceiling.

• Summer (July)

  ○

  5636.6 lux in the morning, 5665.8 lux at noon, and 4075.0 lux in the evening;

  ○

  131% more light in the morning, 134% at noon and 202% more light in the evening compared to a flat ceiling.

Compared with the diagonal ceiling, it receives 9% less light in the morning and 1% less light at noon, but 11% more light in the evening.

• Advantages:

• Highest performance in all seasons: It has the best light reflection and distribution systems;
• Superiority in the evening hours: Even when the evening sun shines at low angles, light reception is high;
• Esthetic advantage: This provides a modern esthetic appearance from an architectural perspective.

• Weaknesses:

• Cost and application difficulty: Due to its complex structure, it may be costlier than other ceiling designs (Table 4).

Table 4. Curved ceiling daylight levels of design studio, TOBB ETU.

Semester	Month	Ceiling Type/Light Flux (Lux)
		Curved
Spring	21st January
		9.30	12.30	15.30
	21st February
		9.30	12.30	15.30
	21st March
		9.30	12.30	15.30
Autumn	21st May
		9.30	12.30	15.30
	21st June
		9.30	12.30	15.30
	21st July
		9.30	12.30	15.30
Summer	21st September
		9.30	12.30	15.30
	21st October
		9.30	12.30	15.30
	21st November
		9.30	12.30	15.30

Table 4. Curved ceiling daylight levels of design studio, TOBB ETU.

Semester	Month	Ceiling Type/Light Flux (Lux)
		Curved
Spring	21st January
		9.30	12.30	15.30
	21st February
		9.30	12.30	15.30
	21st March
		9.30	12.30	15.30
Autumn	21st May
		9.30	12.30	15.30
	21st June
		9.30	12.30	15.30
	21st July
		9.30	12.30	15.30
Summer	21st September
		9.30	12.30	15.30
	21st October
		9.30	12.30	15.30
	21st November
		9.30	12.30	15.30

Table 5. Comparison of flat, diagonal, and curved ceiling types in terms of season, months, and hours (Design Studio, TOBB ETU).

Semester	Month	Hour	Ceiling Type/Light Flux (Lux)
			Flat	Diagonal (30°)	Curved
Spring	21st January	9.30	Flat (1259.4 lx)	Diagonal (2607.9 lx)	Curved (2916.5 lx)
		12.30	Flat (1260.8 lx)	Diagonal (3216.4 lx)	Curved (2929.2 lx)
		15.30	Flat (207.7 lx)	Diagonal (1205.6 lx)	Curved (1509.8 lx)
	21st February	9.30	Flat (1609.5 lx)	Diagonal (3347.0 lx)	Curved (3717.5 lx)
		12.30	Flat (1630.7 lx)	Diagonal (3977.9 lx)	Curved (3957.1 lx)
		15.30	Flat (531.5 lx)	Diagonal (1938.7 lx)	Curved (1522.5 lx)
	21st March	9.30	Flat (1987.5 lx)	Diagonal (4229.6 lx)	Curved (4843.5 lx)
		12.30	Flat (1956.1 lx)	Diagonal (4718.6 lx)	Curved (4086.8 lx)
		15.30	Flat (819.4 lx)	Diagonal (2604.1 lx)	Curved (3100.8 lx)
Autumn	21st May	9.30	Flat (2496.3 lx)	Diagonal (5351.2 lx)	Curved (6093.8 lx)
		12.30	Flat (2395.8 lx	Diagonal (5767.4 lx)	Curved (5557.8 lx)
		15.30	Flat (1292.8 lx)	Diagonal (3620.1 lx)	Curved (4024.3 lx)
	21st June	9.30	Flat (2482.0 lx)	Diagonal (5317.7 lx)	Curved (5978.1 lx)
		12.30	Flat (2479.8 lx)	Diagonal (5774.1 lx)	Curved (5653.6 lx)
		15.30	Flat (1376.4 lx)	Diagonal (3732.2 lx)	Curved (4217.2 lx)
	21st July	9.30	Flat (2436.9 lx)	Diagonal (5148.6 lx)	Curved (5636.6 lx)
		12.30	Flat (2420.4 lx)	Diagonal (5831.4 lx)	Curved (5665.8 lx)
		15.30	Flat (1349.4 lx)	Diagonal (3676.4 lx)	Curved (4075.0 lx)
Summer	21st September	9.30	Flat (1941.9 lx)	Diagonal (4341.0 lx)	Curved (4659.9 lx)
		12.30	Flat (1845.9 lx)	Diagonal (4673.1 lx)	Curved (4417.7 lx)
		15.30	Flat (671.5 lx)	Diagonal (2326.8 lx)	Curved (1611.8 lx)
	21st October	9.30	Flat (1617.9 lx)	Diagonal (3657.4 lx)	Curved (3972.3 lx)
		12.30	Flat (1447.1 lx)	Diagonal (3806.0 lx)	Curved (3473.2 lx)
		15.30	Flat (270.1 lx)	Diagonal (1375.5 lx)	Curved (943.7 lx)
	21st November	9.30	Flat (1280.4 lx)	Diagonal (2847.0 lx)	Curved (3049.2 lx)
		12.30	Flat (1.4 lx)	Diagonal (3099.6 lx)	Curved (2847.8 lx)
		15.30	Flat (1.4 lx)	Diagonal (765.7 lx)	Curved (1313.2 lx)

is a comparison of flat, diagonal, and curved ceiling types in terms of season, months, and hours. According to these analyses:

• Curved ceiling: Provides the best light intake throughout the year. This is the optimal solution considering the season, time, and amount of light. It also provides effective results when light is limited, such as during winter and autumn;
• Diagonal ceiling: It shows a strong performance in summer and spring. It can be considered an effective alternative in case of budget constraints;
• Flat ceiling: It is inadequate compared with alternatives and does not have the potential to increase the amount of natural light entering the classroom. It is important to replace existing ceilings (Table 5).

The use of contemporary techniques developed to ensure visual comfort in buildings and reduce lighting-related energy consumption is becoming increasingly widespread. This study compared the performance of different ceiling types designed to increase the amount and distribution of daylight. In this study, the light reflection and distribution capacities of flat, diagonal, and circular surfaces are investigated. The research questions focused on the extent to which these designs increase daylight integration into the interior space, how they improve the reflection and distribution quality of light, and what advantages curved surface ceilings offer compared to diagonal ceilings.

4. Discussion and Conclusions

This study compared the performance of different ceiling types designed to increase the amount and distribution of daylight. The study was structured to address the research questions formulated at the outset, and in line with this framework.

Q1. To what degree will Pro-Sun improve energy efficiency, light distribution, and homogeneity of daylight in the studio’s interior space?

The data obtained in

Table 6. Evaluation of energy efficiency, light distribution, and homogeneity of flat, diagonal, and curved ceilings.

Feature	Flat	Diagonal(30%)	Curved
Light Distrubition	Irregular and inadequate	wider spread	homogeneous and balanced
Lighthing Homogenity	%30	%60	%90
Energy Effiency	300W	200W	150W

were calculated using the formula (E = A × ΔL × U) [31]. Accordingly;

• E: Energy savings (measured in Watts);
• A: Illuminated area (measured in m²);
• ΔL: Increase in natural light gain (measured in lux);
• U: Energy conversion coefficient of the artificial lighting system (measured in Watts per lux).

According to Table 6, flat surfaces exhibit irregular and inadequate light distribution, resulting in poor performance. In contrast, diagonal surfaces provide a wider spread of light, while curved surfaces offer homogeneous and balanced light distribution, making them the most effective option. Lighting homogeneity varies significantly across the surface types. Flat surfaces achieve a low homogeneity level of 30%, whereas diagonal surfaces improve this to 60%, indicating moderate performance. Curved surfaces demonstrate the highest level of homogeneity at 90%, ensuring superior lighting quality. Energy efficiency also differs markedly between the surfaces. Flat surfaces consume 300 W, making them the least energy-efficient. Diagonal surfaces reduce energy consumption to 200 W, showing better performance. However, curved surfaces require only 150 W, making them the most energy-efficient option. Consequently, curved surfaces outperform both flat and diagonal surfaces in all evaluated aspects, making them the optimal choice for applications requiring effective light distribution, high lighting homogeneity, and reduced energy consumption. Deeper daylight reaches the space, reducing the need for artificial lighting and offering significant energy-saving potential.

Q2. What is the difference in daylight integration between diagonal and curved ceiling designs within the studio’s interior space?

This study evaluated the light reflection and distribution capacities of flat ceilings, diagonal ceilings, and ceilings with circular surfaces. The use of daylight in interior spaces not only reduces energy consumption but also increases user comfort and efficiency. In this context, the study revealed the limitations of flat ceilings, which show low performance, particularly in winter and late hours of the day. According to the simulation results, flat ceilings cause insufficient lighting in the deep parts of the space because they reflect daylight only in the direction of the angle falling on their surfaces. In contrast, the diagonal ceiling type increases performance by reflecting light from a wider angle, but it cannot provide a homogeneous distribution. The curved ceiling design has emerged as the most suitable solution in terms of both energy savings and user comfort. It was determined that flat ceilings must be modified or improved. With the flat ceiling, the lux values were generally low, and there was an imbalance in the light distribution. In winter, light performance decreased significantly during the evening hours. The diagonal ceiling directed daylight better during winter and summer. It reached its maximum performance at noon. The diagonal ceiling provided homogeneous light distribution throughout the day and carried daylight deeper into the space. It exhibited superior performance, even in the evening (

Table 7. Evaluation of diagonal and curved ceiling types in terms of semesters and hours.

Hour	Semester	Month	Flat	Diagonal (30°)	Curved	Suggestion
9.30	Spring	January	1259.4 lux	2607.9 lux	2916.5 lux	Curved
12.30	Spring	January	1260.8 lux	3216.4 lux	2929.2 lux	Diagonel
15.30	Spring	January	1260.8 lux	1205.6 lux	1509.8 lux	Curved
9.30	Summer	July	2436.9 lux	5148.6 lux	5636.6 lux	Curved
12.30	Summer	July	2420.4 lux	5831.4 lux	5665.8 lux	Diagonel
15.30	Summer	July	1349.9 lux	3676.4 lux	4075.0 lux	Curved

).

The curved ceiling type showed the highest performance with its ability to reflect light in multiple directions. This design provides effective lighting, even during the morning and evening hours, and contributes significantly to energy savings. The diagonal ceiling type presented better performance compared to flat ceilings but could not reach the efficiency of curved ceilings. Therefore, the research questions focused on the extent to which these designs increase the integration of daylight into the interior space, how they improve the reflection and distribution of light, and the advantages curved ceilings offer over diagonal ceilings. In addition, the curved ceiling can direct daylight and allow light to reach deeper into the interior. In particular, in the morning and evening hours, the curved ceiling showed a higher performance than the other designs. The results obtained with the VELUX Daylight Visualizer simulation program used in the study revealed that the curved ceiling provided homogeneous lighting, even in the morning and evening. It was, therefore, determined that this design was sensitive to seasonal changes throughout the year and could equally distribute light to every corner of a space.

This study revealed that ceilings are a solution that maximizes the potential for utilising daylight in interior spaces. The results of this study, which was conducted in a design studio, provide valuable information for more efficient utilisation of daylight, especially in educational buildings. The curved ceiling type appeared to be the most effective option in terms of energy efficiency, user comfort, and esthetic value. This study emphasized the necessity of considering the effective use of daylight as a priority to achieve sustainable design goals.