As I write, I recall northern hemisphere school days and classrooms which I remember as being pleasant and happy spaces.
One such overlooked wide playing fields surrounded by trees and distant rolling hills. It must have faced east because I remember morning sun and the changes of light within the view as the day progressed.
I also recall that the walls of the small room, accommodating some 25 of us, were painted in cheerful colours, predominantly yellow (this was a ‘progressive’ Rudolf Steiner school!) and that plentiful daylight meant that ‘the lights’ were not needed during much of the year. However, in darker winter afternoons natural light was replaced by switching on ‘tube lights’ – late 1950’s linear fluorescent fittings with basic diffusers.
When the time came to switch on the electric lighting, I recollect a sense of deprivation – not so much of there being less light (although, to a degree, that may have been the case) rather, it was the loss of some kind of indefinable quality and a resulting negative feeling. It was as if something vital had been drained away, leaving only token illumination.
In the USA the 2007 Heschong Mahone Daylighting Study of more than 21,000 students showed a dramatic correlation between daylit school environments and student performance, including:
- 20 percent faster progression in mathematics
- 26 percent faster progression in reading
- Increased performance of 5-10 percent when students had window views
A New Zealand ministry of Education survey includes the following quote from a pupil:
“The best classroom in our school is room 10. I like it because at one side of the classroom are huge windows which let in a lot of natural light, and you can see all the peacefulness around you, which makes me feel comfortable.” - Year 6 female
These results and responses are unsurprising when one considers that most teaching is done during daylight hours and that natural light has a high blue content. Naturally lit environments are conducive to maintenance of attention, mental energy, avoidance of mistakes and optimum learning and teaching performance. Additionally, because natural light availability is frequently associated with views, this form of lighting can result in a heightened sense of amenity and well-being.
A further benefit of natural light relates to its potential to conserve energy when engineered to achieve an efficient balance in terms of thermal gain and associated levels of air conditioning. However, this benefit can only be fully achieved if the control of the electric lighting system is designed to respond automatically to varying levels of natural light within the building.
Although the principal requirement for the provision of natural light relates to the needs of students, it should be noted that teachers spend up to 90 percent of their day indoors; they too benefit from buildings with daylight, fresh air and access to views.
So, the question arises as to how much of available external daylight can realistically be employed within a school building? Averagely this might amount to 4-5 percent, but the more important point is how the light is entered and distributed within the spaces. In this regard there are key design considerations:
- Direct sunlight to be avoided – creates glare, heat, distraction and fading of materials
- A view of the sky is desirable to maintain contact with external conditions
- Windows with extended views provide valuable momentary breaks from concentrated work
- As far as practicable, natural light should spread uniformly throughout the full depth of the space; in this regard the ratio of width to depth is critical
- The distribution of natural light, either directly or by reflection, should ensure adequate lighting of desk and work surfaces, as well as walls and ceilings
- Reflection factors and colours of internal surfaces determine efficient distribution and utilisation of natural light – it is generally desirable to ensure values of 90 percent reflectivity for ceilings, 70 percent for walls and approximately 40 percent for flooring material
- Avoid inadvertent and distracting specular reflections from shiny surfaces and materials
- Fully, or partially, glazed internal walls enable ‘borrowed light’ and extended views
- Windows in spaces used for data projection require to have shades or full black out
Peter Brown - partner and head of Education at Melbourne architects, Baldasso Cortese, a strong exponent of natural light in the learning environment, points to the use of clerestory windows and ‘light shelves’ as a good solution to enable daylight and sky views. He also advocates extending the classroom to external spaces when sufficient shelter is available.
He comments on the importance of colour, its ability to modulate attention, assist in way-finding and notes that educational clients frequently have strong views about colour and participate in its selection.
There are downsides to badly engineered natural light. Extreme contrasts in light levels lead to visual fatigue and problems in adaptation between local tasks of reading or writing and their visual context. Students using computers experience eye strain if screens are viewed against the background of a bright window. Likewise, whiteboards or projection screens require to be viewed without competing light from windows within the field of vision.
Whilst natural light is the ‘go to’ form of lighting in educational environments, it invariably requires to be supplemented by electric or ‘artificial’ light.
The Australian lighting code AS/NZS 1680.2.3 recommendation for general classroom and lecture rooms lighting levels of 240 lux represents a basic starting point for what, in reality, is a complex process. When the Building Code of Australia, Part J6 lighting energy limit for classrooms of 8 watts/m2 is added to the mix, things become even more complex.
The objectives of combined natural and electric lighting are:
- An environment free of direct or indirect glare
- Good facial visibility and modelling – students and teacher
- Horizontal and vertical illumination – walls, and what appears on them, are important
- Balanced brightness values enabling comfortable viewing of chalkboards, whiteboards, desktops, laptops and tablets
- Provision of high-quality lighting in any part of the space – teaching is no longer only carried out in a static, frontal, student/teacher relationship
- Adequate levels of illumination for the task, be this at the horizontal desks or on the walls
- Higher illumination for students under the age of 6-8 who have not developed the levels of visual acuity of older students
- Successful visual fusion of natural and electric light
The last of these objectives links to the potential to broadly mimic the changes in colour temperature of external natural light with that of the electric light. Conversely, it raises the opportunity to increase the colour temperature (more blue light) to maintain alertness or decrease it (less blue light) to create a gentler, more relaxed, condition.
This approach is referred to as ‘circadian’ or ‘human centric’ lighting and is based on the use of LED light sources operating with programmed control systems which respond to time of day, external light conditions and/or direct touch panel commands.
Although circadian lighting has been found to be beneficial in health and age care environments it is only recently that it has started to be used in educational environments.
A German study of this lighting technique yielded some surprising results. It found that, using certain lighting scenarios, pupil attentiveness and concentration were considerably increased. In addition, reading speed rose by 35 percent and hyperactivity was reduced by up to 76 percent.
One last thought – because ganglion cells are located within the lower part of the retina and are therefore largely upward facing (to the sky!), cool high colour-temperature light up-lighting to ceilings plays an important role in maximising the beneficial effects of circadian lighting,
The full version of the story will be available in the Nov_Dec issue of INFOLINK | BPN.