Are we experimenting on school children?

Human-centric lighting represents a new way of using light in our lives, but it is understandable that there is some skepticism over its use and its effectiveness. Do we know enough about the technology, for example, to be using it in schools? Is there enough evidence to say that human centric lighting improves productivity at work?  Can HCL help to maintain a smooth circadian rhythm at home?

In a 'Clash of the Lighting Titans' Lux's applications editor John Bullock (a HCL cheerleader) and our technology editor Alan Tulla (a sympathetic skeptic) sit down to compare and contrast their human centric lighting opinions.


(JB) 'Human-centric lighting, unlike previous lighting advancements, puts life at its very heart.

We now know that ‘white light’ is more than a matter of colour temperature and colour rendering. We also know that the natural light spectrum generates subtle signals telling the body whether it should be awake or asleep.

Connecting the technology and the science means that we are able to work more closely with the natural light-dark rhythm of the world.'


(AT) 'Having evolved without artificial light, it would be strange if light did not have an effect on us both physically and psychologically. However, Circadian rhythms are nothing new, they have been with us for millennia.

I strongly believe in the principles behind Human Centric Lighting. Bright sunlight can give you a real boost. Equally, Seasonally Affective Disorder, SAD, is a well-established medical condition that can be treated with high levels of light for long periods of time.

Where I disagree is in what we should do next. More importantly, do we even have enough knowledge to know what to do next?'






(JB) 'Teachers have long complained that it is difficult to maintain students’ attention throughout the day and it has been proven that students suffer from attention-deficit first thing in the morning and post-lunch.

A carefully-tuned system is overcoming these problems by introducing light into the classroom with a higher blue content in the part of the spectrum that subdues sleepiness.

The same system is used at other times of the day when young children may be over-active. At such times, the lighting can be adjusted to reduce the amount of blue light entering the classroom in order to settle the mood of the classroom.'

(AT) 'There has been a lot of experimentation in schools but the results have been quite different. For example, when the children first arrived in the morning, one school used high levels of illuminance and high CCT to boost the students’ concentration ready for the lessons. Conversely, another school did the exact opposite because the children were excited when they first arrived and needed to be calmed down for their first lesson.

A manufacturer who promotes HCL told me that these examples prove that it works. The school just has to decide what effect they want and the lighting can be adjusted accordingly.
The question is, of course, what is a school actually meant to do?  Somebody, somewhere, has to set the controls either to dim down or to increase the illumination and CCT.'






(JB) 'Scientific research on people working or resident within the health system has found that lighting has an effect on health.

Lighting can help recuperation and can ensure that drugs are taken at a time when the body is most receptive.'




(AT) 'No-one doubts the health benefits of natural light. However, when it is argued that a particular illuminance and colour temperature gives improved health outcomes compared with another, I have yet to see incontrovertible evidence one way or another.

One reason is that there are simply so many variables. Apart from illuminance and CCT, it has been shown that the previous adaption level, length of time, frequency, time of day and season all have an effect on health.'






(JB) 'Lighting that can sustain, and improve, cognitive performance is good for both employee and management.

An effective human-centric lighting installation that is finely-tuned to provide a balanced pattern of light to help maintain employee’s concentration is a plus for employers.'



(AT) 'HCL has been heavily promoted as a productivity booster. The argument being that the extra cost of an HCL luminaire is offset by the greater output it prompts. This is a good argument but how can you measure how productivity has been influenced by lighting?

My view is that we should avoid financial arguments about productivity and simply say that HCL lighting produces a better lit environment. No-one argues that good quality office furniture or comfortable chairs increase productivity, so why do it for the lighting?

Research reports staff feeling more productive or more alert. Surely, we need to know if they are actually more productive and alert.'






(JB) 'Human-centric lighting in the home focuses on our need to recuperate from the day. We want to be alive to our surroundings, not exhausted and slumped opposite the TV.

Waking in the morning is a struggle at the best of times, but a pre-programmed boost of blue-enriched light in our living spaces, even before we wake up, makes it easier to face the day in bright fashion.'





(AT) 'A lot of people follow the HCL philosophy without even knowing. Kitchens are cool, while living areas often feature warmer and lower levels of illumination.

I am more sceptical about the claims made that TVs, tablets and smart phones can upset Circadian rhythms. One piece of research I saw involved participants looking at a screen for three hours at maximum brightness. I know that people look at screens for long periods but almost all auto-dim depending on the ambient light level. How is it possible, for example, to isolate the effect of the content on the screen from the luminance or CCT? Surely an action movie keeps you more awake than Gardener’s World?'  



The discussion is continuing in Lux's LinkedIn Group 'Lighting Talk' and you can take part by clicking here.

  • Lux is hosting a special Lighting for Health and Wellbeing conference in London on Thursday 22 September. It's free for all those associated with the management of buildings services. To view the details and register for a place, click on the conference logo or click here.