A well-designed lighting scheme, incorporating both natural and electric lighting, will enhance a space and help to create a pleasant learning environment. Iain Carlile, President of CIBSE’s Society of Light and Lighting, considers the elements that make a good lighting scheme
In a school, good lighting is not simply about ensuring staff and pupils can go about their business comfortably and safely. As a minimum it must provide enough illumination to encourage the fulfilment of school activities, but a well-designed lighting scheme, incorporating both natural and electric lighting, will enhance a space and help to create a pleasant learning environment. So what are the elements that make a good lighting scheme?
When it comes to providing light in schools the best source of illumination for almost all teaching spaces is natural light introduced through strategically located windows and roof-lights. There is some evidence to suggest that spaces with high levels of daylight can have significant long-term health and wellbeing benefits and may even result in improved academic achievement.
Daylight is important in regulating and maintaining biochemical, physiological, and behavioural processes in human beings through their circadian rhythm, or body clock. The primary link to the circadian rhythm is daylight, so it is important that both pupils and staff are exposed to high levels of daylight, particularly in the morning. A lack of daylight can disrupt this system and cause problems such as depression and poor sleep quality, which could lead to more serious problems.
The amount and distribution of daylight in a room will vary depending on the learning environment: typically, art rooms require more daylight while dance studios and lecture theatres will require less daylight. In addition, computer rooms, which often have high heat loads and high-density occupancy, are best located in areas within the building that have limited daylight as this would reduce heat gains caused by the sun. Similarly, a ‘special educational needs’ (SEN) school may require that some rooms have few distractions and, as such, views may need to be temporarily obscured by blinds.
While daylight is dynamic and good for occupant’s wellbeing you can, sometimes, have too much of a good thing in both new and refurbishment projects. For that reason, it needs to be considered at the outset of any design or layout by a lighting designer in order to avoid glare and excess heat from the sun making the room uncomfortable. Failure to properly consider daylight could result in the use of blinds, which will negate any of its potential benefits.
Similarly, where teaching is likely to rely on the use of projection onto a screen, it is important to consider the position of the screen in relation to daylight sources to avoid blinds having to be closed when the projector is in use.
The most effective lighting designs will be those where the architectural form and associated shading system serves to provide adequate levels of daylight throughout a space whilst simultaneously shading it from undue levels of direct sun. If the design is wrong the space will likely be too dark at the furthest points from the façade and too bright adjacent to the façade, a scenario which typically leads to the worst scenario of lights on and blinds closed.
To give advice on this tricky area of lighting design, The Society of Light and Lighting has published SLL Lighting Guide LG10: Daylighting and window design.
Of course, there will be times of the year and times of the day when there is insufficient daylight during normal school hours and at such times electric lighting will be required.
The traditional way of artificially lighting a teaching space is with a regular array of ceiling-mounted light fittings. This approach will ensure a uniform task illuminance anywhere in the space, which is useful in allowing the space to be reconfigured easily in order to accommodate different layouts and uses. The downside to this approach is that it will waste energy by lighting all areas of a space, including the areas not in use and may also appear un-exciting. A more energy efficient and visually appealing, although less adaptable, design can be created by focusing the light on the surfaces where it is needed.
The colour of the artificial light is important. Colour temperature is a measure of a lamp’s colour. A light source with a colour temperature of 3000K will appear warm, slightly reddish white while one with a colour temperature of 5300K will appear as a cold, blueish white. For educational interiors, a light source somewhere between these two extremes, with a temperature of around 4000k will blend well with daylight. Where discrimination between colours is important, for example in an art studio, lamps will also need to have a high colour rendering index – a quantitative measure of the ability of a light source to reveal the colour of an object faithfully in comparison with a natural light source.
Energy used by electric lighting is currently responsible for about one third of carbon emissions in primary schools and nearly half in secondary premises; for educational establishments operating outside of normal daylight hours the figure can be significantly higher.
There are two components to energy use: the power used by the lighting equipment and the number of hours it is in use. The power used by the lighting installation is decreasing as technology evolves. But, no matter how energy efficient a lighting installation is, if the lights are left on when they are not needed then energy will be wasted. The way to prevent unnecessary energy use is to ensure the lighting installation can be controlled effectively.
The best lighting designs take account of natural and electric lighting and are controlled to balance one carefully with the other throughout the working day. Within classrooms, for example, detectors can measure light-levels and whether the room is actually occupied. Detectors can be used to control the electric lighting in rows parallel to the window, to allows individual rows to be automatically switched on and off as the daylight levels change across the depth of the room. For optimum efficiency, this system should be set up to be ‘manual on’, ‘automatic off’ to save energy and prevent the lights being left on unnecessarily. Surface light
The appearance of an interior is affected by its general brightness, which depends on the distribution of light in the room and the lightness of room surfaces. To create a feeling of visual lightness and a pleasant learning environment it is necessary to direct light onto room surfaces, particularly those surfaces that are prominent in the normal field of view. Often these will be the walls but the ceiling may also be included, especially in large rooms. Where workstations are employed using vertical partitions, some light on the partitions will be beneficial and without it the room can appear gloomy and under-lit.
The primary presentation wall, containing the whiteboard, should be of a different and complementary colour and darker hue than the other walls. This helps to reduce eye strain as the viewer looks from desk to board-based tasks and back again. Whilst it may be desirable for lighting efficiency to provide higher reflectance surfaces, a deep tone on one wall will provide visual form to the space and reduce glare.
In addition to lighting the task and room surfaces it is important to fill the volume of space occupied by people with light. It should be remembered that we see the reflected light from surfaces and hence the choice of colour scheme can significantly affect the overall impression of the room.
Cost is always a major concern for both new and refurbishment lighting schemes. Capital and running (operational) costs must be considered together, if they are not then a scheme with a low capital cost might have a high operational cost, which could prove significantly costlier over the lifetime of the scheme than an installation with a more expensive capital cost but a low operating cost. If these two cost elements are paid for from different budgets or by different organisations a conflict of interests may arise.
The input of a professional lighting designer will help develop the optimum lighting solution to deliver a solution that enables students, teachers and other staff to carry out their various tasks safely, efficiently and in comfort