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Adequate illuminance has a great effect on the health, comfort, and performance of pupils. It can be achieved by either artificial lighting or daylighting. Daylighting is usually preferred due to psychological, physiological, and economic purposes. This study aims to improve the daylight provision in existing classrooms, by investigating various retrofit methods for passive daylighting techniques in northerly oriented classrooms at Jordan University of Science and Technology (JUST). Data for this research are obtained using computer simulation. The retrofit methods are evaluated in terms of illuminance levels on the desks plane and the chalkboard. The retrofit methods investigated in this study included improving the material reflectance, adding clerestory to the classroom, lightshelves, anidolic ducts, as well as various combinations between these cases. By comparing the results, and in light of the recommended lighting level by The Lighting Guide 5: Lighting for Education released by Chartered Institution of Building Services Engineers (CIBSE) in 2011, the combination of the clerestory window and the anidolic ducts result in the best results. While CIBSE recommended a target illuminance of 300 lx on desks plane and 500 lx on the board, the combination registers an average of 249 lx–300 lx on the desks plane in all sensors compared to 42 lx–105 lx in the base case, and an average of 275 lx–345 lx on the board for the tested dates compared to an average of 45 lx–115 lx in the base case.

Daylight variability throughout the day makes it an ideal light source for the stimulation of humans’ circadian systems. However, the key criteria, including proper quantity, quality, and hours of access to daylight, are not always present inside the built environment. Therefore, artificial light is necessary to complement the human’s visual and non-visual needs for light. Architectural design parameters, such as window area, orientation, glazing material, and surface reflectance alter the characteristics of both daylight and artificial light inside buildings. These parameters and their impact on lighting design should be considered from the early design stages to attain a circadian-effective design. In response to this need, a design approach called Human-Centric Lighting (HCL) was introduced. HCL places humans, and their visual and non-visual needs, in the center of the design process. It manipulates the light-related factors, such as spectrum and intensity, within the built environment for circadian benefits. The effect of HCL on lighting energy efficiency is still not clear. This paper reviews essential architectural design parameters and their impacts on circadian lighting design, considers the HCL design process and explores the most widely used circadian lighting metrics and standards.

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