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Building for body clocks: How human-centric lighting can improve people’s wellbeing & performance

Over the last few weeks, WorldGBC has been examining the tensions and compatibilities between reducing carbon emissions and improving health and wellbeing in buildings in a series of blogs. In this next piece, Harry Verhaar, Head of Global Public and Government Affairs at Philips Lighting, a member of WorldGBC’s Corporate Advisory Board, looks at the need to focus not on daylighting or artificial lighting, but on “human-centric” lighting.

It is important that when we talk about green buildings we are clear about how we define that term.  After all, to achieve the lowest energy consumption, a building would have no windows, heating, ventilation, air conditioning or electric lighting, but that is hardly putting people at the heart of the design. We therefore need to look at how we develop buildings that optimise the balance between their users’ health and wellbeing and reducing their operational carbon consumption.

The importance of incorporating daylight into building design is recognised by all those involved in developing buildings that focus on the wellbeing of their inhabitants. Having evolved in daylight for millennia, the phenomenon of people spending large amounts of time indoors, beneath artificial light, is – in evolutionary terms – very recent. Light delivers the perfect combination of the right light and spectral content at the right time. On a sunny day, daylight provides 100,000 lux and even a very dull, cloudy and rainy day still provides 2,000 lux, yet indoor light levels are generally a quarter of this or less.

Superficially, an answer to providing more light is to make buildings with 100 per cent glass exteriors. However, as touched on in a previous blog post, there are obvious problems with this solution – not least the carbon emissions from the increased energy needed for air conditioning and heating, which far outweighs that required for efficient artificial lighting. There is also the fact that even with a complete wall of glass, daylight will only reach a small proportion of the building – we need to provide the light throughout the interior.

There are three key benefits of light on human life: visual, allowing us to see small details and experience the world around us; emotional, providing a sense of belonging, feelings of safety, and fostering connections; and biological, regulating our circadian rhythm and influencing our mental functioning. The crucial factor is that these three benefits are interlinked.


Our ability to see small details and our visual comfort changes as we get older, with research showing that visual acuity can vary by up to 35 per cent between groups of 60 and 30 year olds at the same light levels. Older groups are also likely to prefer higher light levels and this will have an impact on their emotional wellbeing. A study in 2013 found that “people who appraise their lighting as good will also appraise the room as more attractive, be in a more pleasant mood, be more satisfied with the work environment and more engaged in their work.”


This emotional wellbeing is not just a ‘nice-to-have’ – it delivers clear, quantifiable benefits. Studies have shown that employees who are mentally and emotionally committed to an organisation are likely to be top performers and will miss 20 per cent fewer work days. In addition, “green-certified buildings demonstrated higher scores on survey outcomes related to job satisfaction, evaluation of management, and corporate engagement. There was a tendency for manager-assessed job performance to be higher in green-certified buildings.”


One of the most exciting areas of development in the field of lighting research has concerned the effect of light on our circadian (daily) cycles. Progress has accelerated since 2000, when researchers discovered a new type of photoreceptor in the eyes, one which powerfully regulates our sleep/wake cycle. Via this photoreceptor, light resets our body clock, which prompts our body and organs to carry out their required functions at any time of day.

By maintaining our circadian rhythm, or body clock, light helps to regulate important processes in our bodies. Studies have shown that the body’s hormone levels rise and fall in a daily cyclic pattern, which is maintained and synchronised by our daily exposure to the light-darkness cycle. In this way, light helps to regulate our biological clock and thus influences many aspects of our physical and emotional wellbeing.

However, today we spend around 80 to 90 per cent of our time indoors, with about a third of it in our workplace, and we obviously cannot simply rely on daylight for our work environments, particularly in those countries where daylight hours become fewer during the winter months.  A recent review of how to evaluate the organisational benefits of better buildings carried out by the Continental Automated Buildings Association, and co-funded by Philips Lighting, highlighted the importance of building design in areas such as absenteeism, employee turnover, job performance and satisfaction.

Designing for daylighting

It is therefore crucial that in developing healthy buildings we design electric lighting in a way that delivers the benefits of natural daylight. The good news is that it is possible to use electric lighting to improve onsome of the aspects of daylight.

For instance, as we have already seen, different groups of people require different levels of light to achieve the same level of comfort. This is an important consideration when accommodating a diverse workforce in the same building and where connected LED lighting has significant advantages, allowing for personalisation, individual user control and much greater flexibility and dynamism in the lighting design.

In addition, research has shown the benefit of different types of lighting for different tasks. Bright light has been proven to enhance concentration, mood and alertness, while dimmed lighting conditions have been shown to improve creativity. This is not just relevant for office environments – research in educational settings found that white lighting that can be ‘tunable’ with a range of presets resulted in concentration improvements in both primary and high school pupils of up to 20 per cent.  In a year-long trial in a French primary school, a new system that allows the teacher to optimise the classroom ambience found that reading speed increased by 35 per cent, while frequency of errors dropped by nearly 45 per cent and hyperactive behavior by around 75 per cent. All of these factors can provide a major boost to children’s enjoyment of their school day and their ability to learn.

Back in the workplace, studies have also found that employees in conditions with blue-enriched white light reported a greater alertness, improved performance and better quality of sleep.

Recent research has built on this, showing that office workers with enough light nutrition experience better sleep and less depression, while a recent article in Sleep Health shows a link between sleep disturbances, including reduced sleep, and absenteeism.

By using a connected LED system, control of the intensity, spectrum and distribution of lighting throughout the course of the day, reflecting the circadian rhythms, is now available.  This will enable building managers to support individuals’ mental resources as well as offer the right type of lighting conditions for typical work activities.

The switch to LED lighting does not just benefit the individual, it can have a massive impact on the environment. Lighting currently accounts for around 15 per cent of the world’s electricity, but with a universal switch to LEDs this could fall to around 8 per cent.  That’s just the start – combining high-efficiency lighting with connectivity and smart sensors can deliver energy savings of up to 80 per cent, bringing a dramatic fall in carbon emissions.

Brought together, the wide range of benefits of connected LED systems can deliver truly human-centric lighting, putting the wellbeing of employees at the heart of building design and carbon emissions: creating a win-win for both individuals and organisations, while safeguarding the environment.


Join the discussion

We would love to hear your views on Harry Verhaar’s ideas in this article. Please send comments and case studies to Colin at

Read the firstsecondthird, fourthfifth and sixth pieces in this blog series

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