What is 'healthy' lighting design?
Andrew Bissell, lighting director of Cundall Light4 asks what healthy lighting design is amongst all the wellbeing buzzwords circulating in lighting talk
Words by: Andrew Bissell
The past few years have seen a huge shift in workplace design and the focus is now firmly on health and wellbeing for all its facets, including lighting design. This change has come about from the introduction of standards and guides such as WELL, Fitwel and the BCO Wellness Matters publication, to name a few. Alongside these more recent documents championing health and wellbeing are the stalwarts of the lighting industry such as the SLL (Society of Light and Lighting) Lighting Handbook, SLL LG7 (Lighting for Offices) and the likes of BSEN12464-1 (Indoor Workplace lighting). These documents focus on our visual needs when lighting spaces.
In addition to the above, you also now have almost weekly case studies, research papers and opinion pieces (such as this) on lighting design and its impact on health, wellbeing, productivity, alertness, sleep quality and so on. Then there’s the BRE’s research project, The Biophilic Office (see p82). The question is, between all these documents and armed with all this knowledge, whether we still actually know what healthy lighting design is.
The phrase ‘healthy lighting’ relates to learned papers such as Measuring and Using Light in the Melanopsin Age (by Prof Robert Lucas and others) and Light as a Circadian Stimulus for Architectural Lighting (by Mark Rea and Mariana Figueiro of New York’s Lighting Research Center), among many more. Equally, the phrase healthy lighting captures all the different badges that the standards, guides and manufacturers now use, such as circadian lighting, human-centric lighting, biodynamic lighting and equivalent melanopic lux.
Although now 10 years’ old, Cundall’s scheme for the RIBA Award-winning repurposing of Bourneville Place, Birmingham, is still an exemplar use of daylight - Martine Hamilton Knight
I keep writing the phrase ‘to keep things simple, healthy lighting means…’ but no sooner have I written the phrase I delete it as the reality is that designing healthy lighting is not simple. Why?
There are a number of reasons. The first and most significant reason is that in the world of lighting (this includes scientists, researchers, designers and professional bodies) there is currently no agreement on what the criteria should be. Furthermore, there is no criteria on what we absolutely shouldn’t do, which is far more of an issue. We will come back to this. Other reasons are more commercial. For example, developers need to see a return on their investment and the sooner the better – does installing a healthy lighting system achieve that? Also, products labelled as ‘HCL compliant’ or ‘Circadian Certified’ or ‘Suitable for WELL’ are more expensive. How do you measure the return on a light fitting with regards to a person’s health and wellbeing?
Where the current healthy lighting criteria are concerned, the WELL standard requires 200 EML (equivalent melanopic lux) vertically at the eye for four hours a day (be careful how you design the lighting for a sit/stand desk). WELL says this could be with daylight but does not insist on it. Rea and others have developed a metric where a result of 0.3 to 0.7 means that you are receiving enough quantity and spectral composition of light at your eye so that your circadian system is being stimulated. Below 0.3 your circadian system is not being stimulated and above 0.7 your circadian system is being saturated and more light will have no additional benefit.
The BCO Wellness Matters document talks about views, the quality of the view, equitable access to views, material colours and brightness. But it offers no defined criteria that could allow you to say that you have absolutely satisfied the document, or indeed that you are about to lease or work in a space which does not satisfy the document.
Cundall’s office in Hong Kong is flooded with natural light from 4.5m-high floor-to-ceiling windows. Some 90 per cent of the workstations have access to views. With circadian rhythms in mind, they also have at least 200 equivalent melanopic lux present from 9am-1pm, which the sensor will automatically reduce if the light levels are too high (after 1pm) - CUNDALL
The SLL Lighting Handbook, released in late 2018, provides a comprehensive explanation of circadian lighting in Appendix 2. In conclusion, however, it also does not offer a set of criteria to follow or meet. So is that it? Should we do nothing and carry on with the blanket levels of uniform light commonplace in many offices? No.
What we do know is that daylight has a positive effect on our health and wellbeing. We know that the shift in colour from sunrise, through midday, sunset and to darkness impacts our non-visual system to reset our body clock and adjust our alertness and sleep. Therefore, healthy lighting design must be about utilising daylight. But what do we do if we cannot do that?
The only reason that every occupant in a building does not have access to good quality daylight, in other words healthy lighting, is money. It certainly isn’t through a lack of understanding of how to design such spaces as this has been done many times in the past. Quite simply the cost of land in cities, especially London, and the cost of building are such that developers must maximise the footprint and building height. Unfortunately, this leads to deep-plan office floors and buildings with little or no quality of view as all the occupants see is the deep-plan office across the street. They sometimes can’t even catch a glimpse of the sky.
Equally, the height of buildings keeps increasing, and Manchester in particular is seeing this currently. In our own office, on the 10th floor, we have recently lost our view of the Derbyshire hills courtesy of a new building two blocks away. Essentially those on the upper floors are OK, but those down at street level, and especially if they are set back from the window, are not going to receive their circadian stimulus from natural light.
Does this introduce a long-term problem for developers? As office workers become more educated about the positive impact of daylight and therefore the detrimental impact of no daylight, will they accept a job with an employer who has signed a lease on a deep-plan office? Will deep-plan offices ultimately have to be knocked down as they are unlettable? Can anything be done to change the buildings to improve access to daylight?
For a solution to promote health and wellbeing, both the visual and non-visual qualities of light were considered in
Cundall Light4’s scheme for QBE Insurance, London
One answer could be to push the adoption of agile working and task-based design. Research has shown that we are more tolerant of sunlight and daylight when undertaking certain tasks compared to others. For example, when we are on the phone we are OK sitting in direct sunlight, whereas if we were at our fixed-screen computer we would pull the blind down. If we think about how we may lay out the interior of an office to make use of this knowledge, then we could position comfy high-back chairs adjacent to and facing towards the external windows. The company could then have a policy that to make and take a call you move to be in one of the window chairs. But what if your day-to-day tasks mean you make very few calls? Well those people could have desk positions nearer the windows or desk positions with the highest quality of views. Equally, those staff who are out of the office a lot are given the desk positions in the middle of the space, which is something we have recently done in our own office.
With some existing deep-plan offices there may be a need to be more brutal and cut out the slab in various places, creating double-height zones to help light enter the office. Obviously there is a loss of floor space with that approach but this could be offset through the use of smaller desks. Would we all accept a smaller desk if it meant access to more daylight? What if we all gave up 150mm off the width of our desk but in return we received 20 per cent more daylight? A similar option would be to move the facade inbound a few metres and provide an external space on each floor. Again the working arrangement could be for the staff to use the space for certain functions (weather permitting).
Another answer, and one which I don’t subscribe to, might be that healthy lighting is provided through electric light alone. With the use of say 2700K (warm) to 6000K (cool) lamps, some fairly basic control and an astronomic time clock, the electric lighting would replicate the shift of colour and could even replicate a shift in light intensity, albeit at a much-reduced level, say 150-200 lux in the morning, 750-1000 lux at midday and back to 150-200 lux in the evening. This approach should be a concern, as if the research shows it satisfies our non-visual needs then it could lead to even deeper-plan offices and some offices with no access to daylight at all.
So, what should we do? While we are waiting for more research to be completed in this area we need to be cautious. What we do know is that we are providing ourselves with the best lit environment if we make use of daylight and all of its qualities. As such this must be the primary light source if we are serious about designing healthy lighting. Daylight has a quality about it which we all instinctively recognise and enjoy. When offered a choice of seating we will head towards a window seat or view. Daylight also provides us with space that is animated. Patterns of light are created and move within a space throughout the day, the intensity of light fluctuates and we enjoy the change as it is natural and connects us to the outdoors.
We need to provide everyone with a view, and statements such as those in the BCO Wellness guide saying ‘views should be provided where possible’ need to change to say ‘views should always be provided’. Providing electric light that follows the colour temperature of daylight and, in a reduced way, the intensity shift throughout the day, can be part of a healthy lighting solution, but should not be the sole solution. Equally, providing a space which is more natural, in that the different areas are lit in different ways, will enhance the feeling that we are connected to the natural environment. Lighting the soffit and not just faking it with recessed LED panels again gives us the sense we are outdoors as the sky is bright and not just the pavement. Is any of this news to us? Not really, but maybe we are now realising that we should have done more.
The final question is who can make the changes needed? I get the feeling from the number of people I speak to that the desire is there to improve our workspaces but the cost of land and construction is currently an issue. Then again, we are seeing that clients will pay more for spaces that have been designed with health and wellbeing in mind. But how much of an uplift is daylight worth? Will it take more than just new research and revised guides? Do we need a statutory document that sets out minimum daylight exposure for indoor workers?
The surveys say
More than half (56 per cent) of the participants in a recent pan-European survey said that they would like better workplace lighting. More than 90 per cent of those asked said they believe their work lighting can impact their mood, 87 per cent said it affects their performance and 92 per cent said it influenced their vigilance in the workplace.
The survey, conducted as part of the EU-backed Repro-light project, involved 1,100 workers across Germany, Spain, Italy and Austria. Conducted by consortium members Bartenbach, a lighting consultant, and Mondragon University, Spain, this first phase of the project set out to investigate what end-users really want in their workplace lighting ‘in order to develop a user-centric lighting design solution for the future’.
Participants were asked to consider their working environment’s lighting and what changes they would like to see that could improve their productivity, mood and performance. The level of dissatisfaction was ‘astonishingly high’, says Repro-light. ‘Workspace lighting should follow a strict lighting design code – EN. 12464-1 – which guarantees, for instance, that a certain level of brightness is reached in a workplace. The survey showed that the individual requirements for the lighting differ, showing that personalisable lighting is needed to satisfy all the users.’
The results also showed that people over 50 were particularly keen to have better workplace lighting, and that women were significantly more likely to encourage improvements. The survey revealed that 80 per cent of those questioned would like to have workplace lighting that automatically adapts to personal needs, and more than 75 per cent wanted their work light to change colour when it turns dark outside.
‘Change is required in working environments, both industrial spaces and in offices, and people are now ready for the next large steps in lighting transformation,’ said Repro-light. ‘They are demanding personalisation, automation and adjustability to match their requirement and, most importantly, to boost productivity and general wellbeing.’
- UK productivity could rise by eight per cent, equivalent to £20bn in GDP, if workplaces were created using ‘human-centred design’, according to research by UCL and global consultant Atkins
- The World Green Building Council has linked improved lighting design with up to a 23 per cent gain in productivity
