Education, How to Light

How to Light: Three more ways to light a classroom

It’s back to school for our resident boffin this month, as we cast a designer’s eye over classroom lighting

It is often said that lighting is for people rather than buildings. This is doubly true for classrooms. The lighting should facilitate learning by passing on information from the teacher/lecturer or other media. This makes the designer think more holistically.

There are no longer serried ranks of desks but, often, individual tables where students work in groups. The blackboard has gone, but you’ll need a lot of light on the walls for the whiteboard, flip charts, notices and bookshelves.
The best guidance is Lighting for Education, LG5, 2011 published by the Society of Light and Lighting and the Department for Children, Schools and Families (now the Department for Education). 

There is a lot of emphasis on the benefits of daylight, but this may not be possible in a retrofit scheme. What is crucially important is the mean cylindrical illuminance – basically the illumination on the students’ faces. LG5 recommends more than 150 lx.

 LG5 recommends 300 lx for the task areas (more for specialist areas). Teachers need 500 lx. This is simply a result of their age and reduced visual acuity. I shall depress you no more, dear reader. 
Classrooms come in as many shapes and sizes as the kids. Our classroom measures 9 x 7.25m with a 2.6m-high ceiling. 

Lighting can represent 30 per cent of electrical consumption in schools, so make sure the luminaires are dimmable and linked to a daylight harvesting system.

Flat, in every sense

Flat, in every sense

This 600 x 600 flat panel option highlights some of the pros and cons compared with other solutions. It looks like a good solution: the microprism diffuser isn’t glary; the UGR is less than 19; it uses the fewest luminaires and has the lowest installed electrical load. We used a good quality panel – my opinion of the cheap ones can’t be printed. 

We are achieving 380 lx on the task and 170 lx Ev on the walls. But the cylindrical illuminance is only 115 lx. This is not OK for videoconferencing or for reading students’ faces.
The optical efficiency of the luminaire is partly a result of the polymethyl methacrylate (PMMA) diffusing panel. This is far less resistant to fire than materials such as polycarbonate. 

Finally, unless you have a really pale coloured floor, the ceiling will appear dark compared with the rest of the room.

TECH SPEC

Luminaires 600 x 600 recessed flat panel
Optical control Microprism PMMA lens
Arrangement 2 x 3
Average horizontal illuminance on desk 378 lx (cylindrical illuminance 115 lx)
Electrical load 4.5W/m2
Pros Low running costs
Cons Is it really what you want for a classroom?

Ticks all the boxes

Ticks all the boxes

Here we have a single-lamp T5 in a surface-mounted luminaire. This has two separate optical components. A small amount of light is directed straight down through a diffuser. However, more of the light is reflected off the ‘wings’ giving a softer and more pleasant appearance to the luminaire. This extra sideways light boosts the vertical illumination both on the walls and the students. 

We are achieving 335 lx on the desks and 215 lx on the walls. Again, the cylindrical illuminance is 185 lx. This easily meets the requirements of LG5.  It ticks all the boxes. 

The disadvantage is the electrical load, which is about 50 per cent higher than the flat panel option. There is a big caveat to this because flat panels vary enormously in performance and so do ‘wing’-type T5 luminaires.

TECH SPEC

Luminaires  Single lamp T5
Optical control Microprism and indirect reflected
Arrangement 3 x 3
Average horizontal illuminance on desk 335 lx (cylindrical illuminance 185 lx)
Electrical load  6.9W/m2 
Pros Functions well;  good quality scheme
Cons Highest load in W/m2

A pleasant space

A pleasant space

This achieves similar lighting levels to the surface-mounted scheme but lights the ceiling better and uses 25 per cent less power. Slim, direct/indirect suspended T5 luminaires are an efficient way to light rooms because little light is lost in the luminaire – it has a high LOR. This model has a sharper than usual longitudinal cut-off so the end walls are less bright than the sides. This makes images and text on interactive whiteboards more legible.

As a rule, rooms lit by this method look bright and airy, but watch the cut-off angle to avoid dark walls.

The electrical load is only slightly more than that of the flat panel scheme but it is a vastly better lit environment.

One disadvantage of this scheme is that some schools don’t like pendant luminaires.

TECH SPEC

Luminaires Direct/indirect T5. 
Optical control Reflector and louvre
Arrangement 3 x 3
Average horizontal illuminance on desk 325 lx (cylindrical illuminance 185 lx)
Electrical load 5.25W/m2 
Pros Plenty of light on the ceiling
Cons Check the available ceiling height