Daylight vs electric light
All light is not created equal.
One key difference between daylight and electric light is daylight’s changing intensity, colour and direction, through the day and night, and across the seasons – all of which have an impact on the variation of perception within a space.
The direction in which light falls is also dependent on the location of windows and lighting fixtures. Daylight penetrating through façade windows, roof windows or skylights will provide a more diagonal light direction, while electric lights in the ceiling provide more vertical illumination.
Daylight within a space gives a suitable mix of direct and diffused light. This mix enhances the three-dimensional perception of objects by providing true-to-life shadows and reflections.
A space with only diffused light will miss the direct light component, which helps us to discern shape and structure, and such a space can be perceived as dull and unappealing.
Most people would probably agree – perhaps without knowing exactly why – that daylight makes us feel good. Daylight is generally associated with health, alertness and inspiration.
The reason is linked to how the human body and mind are regulated by circadian rhythms. To maintain overall good health, we need appropriate light signals during the day, as well as darkness at night. For example, light in the morning helps to synchronise our biological clock and increase our alertness, paving the way for increased performance during the day.
Electric light certainly has a role when designing with circadian rhythms in mind, especially with modern advances such as LED lighting. But it cannot replace daylight. The colour composition of daylight is rich in the wavelengths that support our circadian rhythms, and bright at the times of day that are most important to these processes. This reinforces how important it is for architectural design to makes good use of daylighting.
How daylight improves performance
Daylight affects our health and alertness. It also has a long-standing reputation for improving the performance of students and workers alike.
Studies going back to the 1980s have found that daylight improves mood, enhances morale, diminishes fatigue and reduces eyestrain. Companies have also discovered that, after relocating to buildings with better daylight conditions, performance and productivity usually improve.
Among others, a study from 2002² demonstrated that learning environments infused with natural daylight result in more effective learning.
This study found that students in classrooms with the greatest window area or daylight levels achieved significantly higher scores (7-18%) on standardised tests, than students with the least window area or daylight levels.
Tips for designing classrooms
Here are three tips that architects and designers should consider when designing classrooms:
- Use daylight as a main source of lighting, with electric light as an important secondary source, especially when there is not enough daylight outside.
- Integrate daylight into the overall school design: successful architectural daylight solutions are well integrated and combine the advantages of windows, both in the façade and in the roof.
- Daylight is highly important, but don’t forget the view. A study of office workers³ concluded that a natural view is preferred over a view of man-made infrastructure. More specifically, workers appreciated information about exterior conditions – notably location, time, weather, nature, etc. Skylights and roof windows are especially effective at achieving this.
- Clever Classrooms (2015), Summary report of the HEAD project, University of Salford, Manchester.
- Heschong, L. (2002) Daylighting and Human Performance, ASHRAE Journal, vol. 44, no. 6, pp. 65-67.
- Christoffersen, J., & Johnsen, K. (1999). Vinduer og dagslys - en feltundersøgelse i kontorbygninger. Hørsholm: SBI forlag. SBI-rapport, Bind. 318.