Did you know? Making good use of daylight in a classroom can reduce lighting costs by 19%.
Natural window light has long been known to positively affect mood, energy and concentration. However, a familiar scene in classrooms and offices is the use of blinds to control glare when it is bright outside. This is particularly common when whiteboards and projectors are being used, as many models are not bright enough to view in strong natural daylight. Often the blinds are left drawn, with lights switched on, even when the whiteboard or projector is switched off. Where possible, staff and pupils should be encouraged to use blinds to direct daylight onto the ceiling and walls instead of closing them completely. This should reduce the need for electric lighting in the classroom whilst reducing glare.
Another common problem in schools is windows partially obscured by resources and displays. Keeping windows clear helps to optimise the amount of natural light entering a room.
In many schools, classrooms can have excessive lighting installed. This is often arranged so that individual rows of light fittings can be switched separately. Follow the steps below to identify those lights which do not need to be switched on under normal daylight, and to implement a programme to ensure they remain switched off.
- With your Energy Team, identify which rooms in the school have multiple light switches which allow rows or groups of fittings to be controlled independently.
- Choose a day with average levels of daylight (i.e. overcast day/not too sunny) and carry out the following procedures in each room.
- Switch off all the lights and then, starting furthest from the window, switch each row back on one at a time. Each time consider whether there is an adequate amount of light to work effectively at desk level. (Note: in some classrooms, it is lighting installed close and adjacent to an internal wall that is best left off).
- When you feel there is an acceptable amount of light in the room, stop switching.
- In consultation with the class teachers in these rooms, discuss your findings and get their agreement as to which rows of lights could normally be left switched off. If teachers are uncertain about progressing this, try switching off one set of lights nearer the window and see if the pupils notice in the next class.
- Once identified, mark up the respective switches with red stickers in order to indicate to the staff and pupils that these marked switches are not to be used unless necessary (i.e. at night, on a very overcast day, or if a pupil needs more lights on).
- You could also use green stickers for lights/switches that should be used as needed. Red Dots – Do not touch and do not use (override this as necessary at teachers’ discretion) Green Dots – Switch and use lights as required
- Some schools have used different shapes with the colours to assist those that may be colour blind.
Next Steps to save energy
- Design some posters to encourage staff and pupils to open the blinds and switch off lights.
- Consider asking your school caretaker or site manager to remove some of the light bulbs from their fittings in over lit areas of the school.
- Ask your school business manager or site manager to choose the most efficient lighting possible. Upgrade existing light bulbs and fluorescent tubes to low energy LED tubes and lights. LED lighting reduces energy use and heat output, eliminates flicker and hum, extends lamp life (by up to 50%) and can allow dimming – all of which can make a classroom more comfortable. Make sure this happens by asking the school management team to include it in the school’s purchasing policy.
- Ask your school business manager or site manager to consider occupancy and daylight sensors in problematic areas of the school: By dimming or switching off lighting when there is nobody in a room occupancy sensors can reduce electricity use by 30%. Adjusting the artificial lighting according to the amount of natural light in a room using daylight sensors or photocells can reduce electricity use by up to 40%.
- Discuss with your school business manager or site manager a maintenance schedule which includes cleaning windows, skylights and fittings, checking and replacing old and dim lamps, ensuring controls are in good order and set properly, cleaning occupancy sensors if installed. Without regular maintenance, light levels can fall by 30% in 2–3 years.
- When possible, position computers in classrooms so that they are parallel to the window wall, their monitors face a blank wall, and there are no windows behind the user. This means natural light can be used more often without glare problems.