Visual and Non Visual Effects of Lighting in Educational Building And Design Strategy Development

This study investigates the visual and non-visual (circadian) effects of lighting in educational buildings, with a particular focus on evaluating and improving daylight and electric lighting performance in university classrooms. The research addresses the limitations of current lighting practices in meeting both visual comfort and biologically effective light requirements and proposes design strategies to optimize these conditions. Within this context, light is considered not only as a visual medium but also as a key regulator of circadian rhythms, influencing occupants’ health, alertness, cognitive performance, and well-being. Humans have evolved to adapt to the day-night cycle dictated by solar movement; however, modern indoor lifestyles have created a biological mismatch. In environments where users spend extended periods, such as educational buildings, lighting design must address the regulatory role of light in human physiology, specifically its role as a zeitgeber (synchronizer). Despite growing understanding, lighting design in classrooms is still predominantly based on conventional visual performance criteria such as horizontal illuminance and glare control. Increasing scientific evidence indicates that these parameters alone are insufficient to ensure biologically effective lighting conditions that support circadian rhythms, alertness, and well-being. Consequently, a gap remains between traditional visual lighting design approaches and the emerging need to consider non-visual effects of light within the classrooms. Emphasis needs to be paid to the spectral power distribution of light entering the visual system, thus increasing the importance of the vertical plane at eye-level, beside horizontal work planes.  

The problems addressed in this study can be summarized under three main categories. First, conventional lighting standards primarily evaluate visual performance, often overlooking non-visual biological responses to light; this is also due to the existing standards for electric lighting, such as EN 12464-1:2021, while to date no formal standard has been set to address circadian lighting requirements. Second, architectural and spatial design parameters such as façade orientation, glazing properties, external obstructions, and internal layout, which determines the seating configurations, may significantly influence circadian light exposure but are rarely evaluated together within an integrated framework. Third, the interaction between daylight and electric lighting strategies in classrooms remains insufficiently explored in relation to circadian-effective lighting metrics. The limitations of conventional, one-size-fits-all electric lighting grids ignore the temporal and pedagogical needs of modern classrooms. The purpose of the study is to evaluate the visual and non-visual lighting performance of a sample of selected university classrooms and to develop design strategies that support circadian-effective lighting conditions while maintaining acceptable and standard-compliant visual comfort. In this context, the research aims to examine how architectural configuration, environmental conditions, advanced technology, spatial organization, pedagogical behavior, and electric lighting controls can bridge the biological deficits of the "given world". The study uses seven educational blocks of Marmara University Mehmet Genç Campus as a representative case study of diverse architectural typologies. It includes six chapters: 

• In the first chapter, the conceptual and research framework of the study is established. The introduction defines the research problem and presents the conceptual background of circadian lighting in the built environment. A bibliometric evaluation is conducted to identify the main research trends and knowledge gaps in the field.  

• The second chapter provides the theoretical foundation of the study by examining the biological mechanisms of light and the relationship between lighting conditions and human circadian regulation. The chapter reviews international standards and guidelines related to visual and non-visual lighting performance, introduces the fundamental physical characteristics of light, and discusses key circadian lighting metrics. In addition, artificial lighting strategies, human-centric lighting concepts, and evaluation methodologies are reviewed. The chapter concludes with a focus on educational environments, examining the physiological, psychological, and cognitive effects of lighting as well as relevant educational case studies. 

• The third chapter explains the methodological framework of the research. The overall research approach is described, followed by the presentation of the selected case study classrooms. A pedagogical–spatial–lighting integration framework is developed to evaluate the relationship between teaching modes, spatial configurations, and lighting performance. The chapter further defines the site-specific variables and design interventions used in the analyses and explains the procedures for on-site measurements and simulation modelling. 

• The fourth chapter presents the results of experimental and simulation-based analyses. The chapter begins with the validation of the simulation model through in-situ measurements. Subsequently, the performance of visual (photopic) and non-visual (melanopic) lighting metrics is evaluated under existing daylight and electric lighting conditions. Additional analyses investigate the effects of dimming schedules and various architectural and lighting design modulations on circadian-effective lighting performance. 

• The fifth chapter discusses the results in relation to the research questions and synthesizes the findings into integrated lighting design guidelines. The baseline performance of the classrooms selected as case-study is evaluated, lighting deficits are identified, and potential compensation strategies are explored. The chapter further investigates different layouts of activity-based seating configurations and their influence on circadian light exposure. 

• The sixth and final chapter summarizes the overall findings of the study and presents the answers to the research questions. Based on these findings, final recommendations for circadian-oriented lighting design in educational environments are proposed. The chapter also discusses the limitations of the study and outlines directions for future research before concluding with final remarks. 

The study is based on the hypothesis that architectural typology and spatial organization need not be treated as fixed constraints. Instead, the findings suggest that through conditional dimming strategies and activity-based lighting settings, the biological limitations of classroom environments can be partially mitigated, contributing to improved circadian lighting conditions. This is also in line with modern principles of innovative teaching, which also include the possibility of having flexible spaces, where the layout can be changed depending on the lecture type.