Dynamic lighting in offices

How lighting affects the alertness of office workers

In 2017, the Lighting Research Center in New York (the “LRC”) published a study showing huge differences between office workers who work in sufficient light that supports their natural daily rhythm and those who spend whole days in dark, gloomy offices. Effective lighting brings workers several benefits – less stress, less depression and better sleep. A team of LRC scientists led by Dr Mariana Figueiro measured the light levels of 109 participants in 5 federal office buildings designed to let in as much daylight as possible. The scientists found, however, that even open-plan spaces with many large windows do not give office workers enough light to support their biological rhythm. This is due to factors such as the season, cloud cover, the orientation of the desk or the position of blinds.

In response to these findings, the LRC team concluded that additional electric lighting could provide enough light during the day. It should, however, be effective lighting that supports the natural biological rhythm – known as biodynamic lighting. Biodynamic lighting aims to achieve the biological effects of daylight in an artificially lit environment. It is a way of lighting interiors that imitates the cycle of natural daylight by changing its colour temperature and intensity during the day.

They tested their theory in practice – in a new study they installed such lighting for 68 employees in two other US federal government offices and two US embassies that “struggle” with dark spaces. They then evaluated whether this reduced the workers’ sleepiness and increased their alertness, vitality and energy. The US embassies in Reykjavík (Iceland) and Riga (Latvia), close to the Arctic, experience a dramatic drop in daylight every winter as the dark hours grow longer. Federal government offices in Vermont and near Washington, D.C. also have less light in winter, though not as little as near the Arctic Circle. Clearly, in these places not only sufficient but also well-chosen lighting is essential.

The LRC is one of the few institutions researching light and health. In this experiment, special dynamic ceiling lighting and desk lamps were installed in the offices for two days to give employees effective lighting that supports their biological rhythm. After the two-day experiment, participants completed questionnaires on their sleep patterns, stress levels and subjective feelings of overall vitality and energy. The researchers also developed the Daysimeter – a device that measures individual daily light exposure (it records the light stimuli each employee was exposed to during the day) during the two-day trial and in the period before it.

Better lighting = better work performance

The results showed that the office workers received far more light stimuli at work during the two “trial” days than on the baseline day. The employees themselves rated these days positively – they felt less sleepy, had more energy for work and could concentrate better. Workers from 4 different sites (4 buildings) agreed on this. It follows that an employee’s energy, concentration and mood are strongly influenced by the lighting – lighting must be designed effectively and provide enough light stimuli (especially in the morning, so that the mind can “start up” properly). Well-chosen lighting can suppress sleepiness and improve engagement at work.

Today, office lighting in many buildings is designed solely to meet lighting standards, but the LRC points out that it pays to invest more time and money in the right lighting design. Light and darkness received by the eye have a major influence on how the body functions and control important biological processes. Light therefore does more than enable vision (visual function); it also affects a number of biological processes in the human body (biological function). Light can give you an instant boost at any time of day (much like a cup of coffee) and so improve work performance. It also eases seasonal depression, affects the length and quality of sleep and influences brain activity.

High illuminance levels received by the eye during the day lead to:

higher serotonin levels in the brain
a better-set daily rhythm (active day phase and night sleep phase)
greater alertness and concentration during working hours
better mood
improved cognitive function (the ability to think, perceive and learn)
good-quality sleep (thanks to a more stable circadian rhythm)

Light heals, light harms

What exactly is the daily rhythm (biological rhythm)? Internal biological cycles that repeat every day (digestion, hormone production, regulation of body temperature and the timing of sleepiness and wakefulness) are synchronised with the 24-hour cycle of the day. Every organ in the body, every cell and every process regularly changes its level of activity during the day. Synchronising our internal biological clock with the 24-hour cycle helps regulate hormone levels (melatonin, cortisol and serotonin), which are key to keeping the biological system in balance. A lack of daylight can lead to sleep disorders, chronic fatigue or depression.

Daylight is very important in offices and other interiors, as light is a major carrier of information (visual perception accounts for around 80% of all information we take in from our surroundings). Interiors should therefore have a healthy lighting climate: light should not dazzle, as the human eye cannot work well with widely varying brightness levels. Light should be adjustable (because of the ageing eye – as we get older, we see the world as less blue). It is also worth remembering that the colour of light creates the atmosphere of a space and shapes how it is perceived. Workers should feel no visual discomfort, but neither should the lighting be dull and uniform (this leads to eye fatigue, loss of attention and lower productivity). Excessive brightness or contrast is also undesirable, and direct light rays must be avoided.

Natural daylight is dynamic and its intensity changes. As mentioned above, effective office lighting (biodynamic lighting) tries to imitate this natural daylight by changing the colour temperature and intensity of light during the day. It combines controlled natural daylight with artificial light sources, and getting the balance right gives workers optimal light levels. In the morning the light should be brighter and whiter, in the evening dimmer and in warmer tones – but it is not only about changing colour temperature and intensity. What should biodynamic lighting offer?

adjustable light intensity
adjustable correlated colour temperature (tunable light colour)
adjustable direction of light
high illuminance levels
dynamic changes in light level and colour temperature during the day

This type of lighting is beneficial not only in offices, but also in schools, healthcare, homes, public offices and other spaces with limited daylight – wherever people spend a lot of time and cannot regularly get out into daylight for longer periods. It is ideal for countries in northern regions with long, dark winters, but it is also useful in our latitudes.

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Dynamic lighting in offices

How lighting affects the alertness of office workers

Better lighting = better work performance

Light heals, light harms

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Michal Chochlík