Classrooms usually have large window areas providing high levels of natural light and therefore offer the potential for considerable savings but any control scheme must provide the flexibility to meet the varying needs of classroom activities.
Adequate and suitable lighting is essential for creating a comfortable environment conducive to learning. However, as most classrooms feature a large window area, they do offer the potential for considerable savings via daylight harvesting. Indeed, new legislation requires individual photocell control of each row of fittings. Combined movement and photocell control is likely to be the best option, with sensors regulating each row of lights to a different level respective to their proximity to the windows. For example, the row of lights next to the windows would dim to a low level when it was bright outside, the middle row might regulate to 50% of output, and the row furthest from the windows might remain at full output.
To maximise savings, it is a good idea to have lights operate by absence detection. A switch, located by the door, is used to activate the lights on entry. (As a deliberate action is needed to bring on the lights, someone just ‘popping into’ the room might choose not to switch them on at all.) Lights will switch off automatically once the area has been vacated and the programmed time delay has elapsed.
It should also be noted that by default the provision of an absence switch gives the user the option of turning lights off when they leave the space rather than waiting for them to time out, thus further enhancing savings.
As well as having the luminaires grouped in rows parallel to the windows to act together in response to ambient daylight, it is a good idea to create a separate group for the whiteboard lights. In this way, the whiteboard lights can be operated as needed, perhaps dimmed for an AV presentation for example, via a switch at the teaching station. It is also possible to switch or dim the whiteboard lighting according to ambient light levels.
It is suggested that the teacher be provided with two switches: one like that by the door to operate the whole room, the other to operate the whiteboard lights.
Occupancy detection should cover the entire classroom not just the front, teaching desk area. It cannot be assumed that the teaching desk will always be occupied when there is a continued need for lighting. A teacher might spend time in the classroom away from their desk, sorting a cupboard or hanging artwork for example.
Key Considerations and Application Notes
- Daylight harvesting to take full advantage of ambient daylight.
- Each row of lighting must have its own photocell/sensor.
- Absence detection, whereby lights are activated manually, to maximise savings.
- Whiteboard lighting operated as a separate group.
- Occupancy detection of the whole classroom not just the teaching desk area.