Feature, IoT/Smart Lighting

Future of human-centric lighting: step forward HCL 2.0

Sponsored by Trilux

With the principle of human-centric lighting established, it’s time to look beyond colour temperature to a more holistic approach.

Human-centric lighting (HCL) is at a crossroads. The science behind the principle is strong, but there are indications that application of the available technology may be struggling. If we dig a little deeper, we can see where HCL as a standalone concept is lacking.

There are two chief aspects of our lives that can be influenced by an HCL scheme –controlling the production of melatonin in the body and maintaining effective circadian entrainment.

The issue for the lighting community is how to satisfactorily engage HCL technology with the chaotic way that so many of us live. While a proper HCL environment needs to be carefully planned for building occupants, which suggests a robust interventionist control strategy, the lighting technology that is commercially available has suffered from commercial dilution – a symptom of LED commodification. Schemes claiming to be HCL have been implemented that have been little more than tunable-white installations, with little or no regard for a control philosophy as to how they should be used.

But HCL does work. In the very early days of HCL, Andrew Bissell of Cundall said that this kind of lighting could only work in environments where there is 100 per cent control of the environment. Happily, that condition doesn’t apply to many of us, but there are people who live in those conditions, principally in the health and care sectors. Hospital patients and care home residents often live an almost totally indoors existence. And in these cases, the principles of HCL are seen to work. The science can be translated into applied technology after all – but not for most of us.

We need to consider holistic quality of lighting in a project, from concerns around flicker and glare, the psychological impact alongside the physiological, through to the light around the building as well as inside. We call this HCL 2.0

Richard Holt, Trilux Lighting Managing Director

Coming from its position in the vanguard of HCL development and luminaire design, these are the questions that Trilux is asking. ‘We are now looking into the future for human-centric lighting.

Going forward, we need to consider the complete human experience throughout the scope of a project,’ Richard Holt, Trilux Lighting managing director, told us. ‘We need to consider holistic quality of lighting in a project, from concerns around flicker and glare, the psychological impact alongside the physiological, through to the light around the building as well as inside. We call this HCL 2.0.’

Step forward HCL 2.0.

The original focus of HCL was in the manipulation of blue content within artificial light, linking it to the suppression and release of melatonin. But there is more to human-centric lighting.

Back to basics: The core principle of medical practice is first, do no harm. It dates back to ancient Greece, the island of Kos and Hippocrates, sitting under his plane tree. How does lighting do harm? We have to ensure that lighting hardware, and our design approach to light in use, are not producing effects that are less than optimal for human health. This must be the starting point for an HCL 2.0 review.

Technical issues: We need to look at reinforcing technical limits on equipment. The flicker issue in LED lighting is becoming a serious health issue, while glare from LED optical systems causes headaches and worse. Clients and end users need to know that their lighting is not a health hazard. HCL 2.0 needs to specify limiting factors around luminaire performance metrics.

Psychological issues: We must look at the colour-tuning issue again. While it has not been possible to collect confirmatory data on a bio-effective melanopic response, there is sufficient narrative evidence to suggest that colour-tunable lighting can provide psychological benefits for individuals. Two examples are teachers who report better behaviour patterns from pupils when light colour is used as a positive adjunct to lessons, and hospital patients who report improved healing times when light colour is used dynamically as a feature of their environment.

HCL 2.0 must embrace the concept that the colour of white light can have emotional benefits, and ensure that personal spaces have the ability to control colour temperature.

Physical safety issues: Lighting as a straightforward illumination issue has never been on the HCL agenda, on the assumption that good lighting will be safe lighting. But the ability to move people safely around a building and enable everyone to go about their business is of paramount importance and should be included in any HCL proposals. HCL 2.0 needs to include a policy on holistic lighting quality that ensures good quality lighting underpins all other visual and non-visual wellbeing requirements.

Daylighting: Perhaps the most contentious issue is the balance between daylight and artificial lighting. HCL spoke only of artificial lighting parameters – a mindset that actually encourages poor daylighting performance in building design. HCL 2.0 must acknowledge that the root of good health lies in access to the natural world, including daylight. That lies in the design of our buildings, but this needn’t be an uphill struggle. There are fine examples of new buildings where daylight is being used to great purpose and is having an enormous impact on the aesthetic quality of building interiors, as well as demonstrating substantial reductions in lighting energy costs.

The push to HCL 2.0 will not come from a single conversation. It will come from discussion, from example and from a concerted effort to ensure that lighting installations truly are for human beings – and that means all of us.

HCL 2.0 is about understanding and supporting how people live and work 24 hours a day. We have to move beyond thinking just about the eight hours a day a person may spend in an office. We must also use electric lighting as supplementary light, with daylight our dominant and prime source of light.

Andrew Bissell