Lighting for the future

Teaching places very particular requirements on building design. Added financial pressure also means that greater attention must be paid to energy efficiency and how the building can be used for other revenue-generating activities.

Nowhere are the effects of these requirements more evident than in the challenges faced by the lighting designer. One example of cutting edge school design is Witheridge Primary School in North Devon. The aim is to design a classroom of the future, including the lighting strategy. Witheridge school has been designed by The Design Collaborative and work begins on site from January 2003.

The focus is on developing a blueprint for a sustainable school in which environmental quality and low energy consumption influence the design of the buildings.

Maximum use is made of daylighting while the brief for the artificial lighting focused on the need for both direct and indirect lighting: a focus which acknowledges the findings of the most up to date research on effective lighting schemes in areas where workers and students are using computers or carrying out a variety of tasks.

The primary difference between an educational environment and an office lies in the way people interact within the space. Three distinct tasks can be identified which need to be addressed: to encourage interaction between individuals; to focus the attention of many individuals onto a small teaching or demonstration area; and to light the visual task on horizontal and vertical surfaces such as desks, whiteboards and demonstration objects. Increasing use of computers in schools and colleges, means that all the challenges of glare and reflection on screens are added to the equation. The basic principle is one of achieving a well balanced lit environment, or brightness management.

Managing brightness
One of the key achievements of managed brightness is that there will be no sharp contrasts throughout the environment. The eye is an incredibly sensitive organ that adapts quickly to different light levels, but it nevertheless requires effort, and if such adaptation is required constantly throughout the day then the eye will become tired. Typically this will happen if a space is lit only with downlights – the result of this type of lighting is that walls and other vertical surfaces are considerably darker than desktops. Every time the student looks up from their notes to the teacher or display board their eye is required to adapt to compensate for the changing light levels. Do this several hundred times a day and the result is quite likely to be eye strain and headaches.

Bright spots are also tiring and these are usually caused by unshielded lamps. Even at the periphery of vision the eye will be acutely and uncomfortably aware of an area of brightness. Modern lamps are particularly bright (eg T5 or T16) as lamp manufacturers are striving to produce greater output from smaller lamp 'envelopes'. This is why all modern luminaires should be designed to disguise the lamp and remove it from the direct line of vision.

The need for balanced lighting is particularly evident in schools – whatever the teaching method used, students will be receiving information from a teacher who is likely to be standing or moving around the space. Good lighting on the face at standing head height and lighting that takes into account the fact that the focus of attention will constantly shift is extremely significant.

The increasing use of computers in all educational establishments means that the elimination of glare and reflection must also be considered. This consideration is always made more complex by the fast changing nature of computer screens. Each has its own angle and level of reflection and there is little uniformity.

Design guidance
The addendum to Lighting Guide 3 means that the guidance can no longer be interpreted as being prescriptive, but relies heavily on the expertise of the lighting designer to understand and implement the lighting strategies proposed. In effect, the guidance explains the desired results of a good lighting scheme but leaves the designer free to reach that effect by whatever means he finds to be most effective.

Where the standard is most explicit is in its firm recommendation that good lighting can only be achieved by a combination of direct and indirect lighting. This is most likely to be achieved by the use of suspended luminaires designed to direct a proportion of their luminance up to the ceiling. Wall washers and dedicated uplighters can also be added to the mix to ensure a well balanced lit environment.

The challenge for offices in implementing this advice is often the lack of ceiling height – clearly a suspended luminaire requires a higher ceiling than a recessed fitting and it will, in turn, increase the sensation of space by throwing light up onto the ceiling and emphasising the sensation of openness. Rooms lit purely by recessed downlights will have a shadowy ceiling that is instantly oppressive and gloomy. Older schools are less likely to suffer from low ceilings, and indeed, the challenge here may be one of effectively lighting high Victorian ceilings without wasting energy or compromising the lighting quality on the working levels.

In lecture halls or demonstration areas the lighting will need to be more flexible, controllable and capable of creating different effects. Clearly whenever images are projected onto a screen the lighting must be instantly dimmable and also carefully controlled. Stray or interreflected light falling on the projection screen will ruin the clarity and colour rendition of images; lighting into the eyes of students will produce a veiling luminance which causes the same effect. Luminaires with narrow cut-off angles can provide control of interreflected light while at the same time ensuring a minimum (>15 lux) level for the writing of notes by students.

And finally there is an aesthetic consideration. While most attention is likely to focus on the effectiveness of the lighting design there is still room to consider the visual impact of the luminaires themselves within the space. In the Witheridge School project Zumtobel Staff's Spheros luminaire was specified as much for its strong elliptical shape as for its ability to distribute light evenly along the working plane and the ceiling. The conclusion of the specifier was that as each luminaire is to be in the sight lines of both students and teachers the chosen product had to have a strong design impact in its own right.

Finally there is a consideration of the effect of lighting on the wider issue of performance. Research into the impact of poor lighting on workers indicates that that one element of a work space will have a tangible and considerable impact on their productivity. Alertness, the ability to maintain concentration over a prolonged period and even the mood of the individuals are all affected. Clearly this research is used primarily by commercial operations with a financial interest in maximising the productivity of their workers – but in an ideal world, surely the performance and achievements of our schoolchildren and students is of even more importance for our collective future.