Feature

How to create a bespoke human-centric lighting scheme

Sponsored by Tamlite

There are a number of basic elements that need to be addressed when putting together a human-centric lighting specification.

Luminaire specification

The components that go into any luminaire must guarantee an appropriate level of performance. Apart from the obvious tests to ensure that the luminaire meets all electrical and mechanical test requirements, the luminaire should also be tested to ensure that LED flicker is kept to an absolute minimum.

 

Flicker

Unfortunately, not all flicker is visible, but the consequences can still be damaging. If left unchecked, flicker can result in chronic discomfort such as eye-strain and headaches, which can lead to increases in absenteeism.

LED lighting is simply an electronic circuit, but in that simplicity lie potential problems. Flicker comes from a mismatch of components – the LED module, the driver and the control system all need to fit together to create a single circuit. For a fully-compliant human-centric lighting specification, the manufacturer must be able to guarantee that flicker has been minimised.

 

Light distribution

Not all luminaires are appropriate for a human-centric installation. There are design criteria that need to be satisfied and a lot of general-purpose commercial lighting fixtures cannot meet those criteria. There are positive and negative connotations to this.

The negative: the distribution of light from a luminaire needs to ensure that the visual appearance of the luminaire in the working space does not create glare. Glare can cause health problems in the long term because of excessive brightness entering the eye; overly-intense luminaires can be reflected in working equipment (such as screens) that prevent the equipment from being able to read data.

The positive: scientists have identified that a minimum level of light needs to enter the eye if the body is to maintain its proper alignment with the natural daily (circadian) rhythms. This is usually achieved using a combination of quality luminaires and spacing of those luminaires in the working environment.

 

Light quality

LED light quality has improved by leaps and bounds over the last few years. The latest development in LED colour comes from the desire to match colour output with the natural light spectrum. Human-centric lighting schemes are designed using ultra-high colour rendering LEDs, typically achieving colour accuracy higher than 95 per cent. (Technical note: this translates to a CRI (colour rendering index) value of 95 or a TM30 metric of Rf93 (colour fidelity) and Rg (colour gamut) of 100.)

There is also a drive to move colour accuracy performance even further, using ‘sunlight’ criteria for LEDs. These LED modules are designed to mimic the spectrum of sunlight. In doing this, LED manufacturers are seeking to reduce the blue spike – usually inherent in the LED spectrum – which will lead to key health benefits.

 

Circadian cycle

The natural cycle of light and dark can be interrupted in modern cities. The negative result is that our bodies, which have evolved over many thousands of years to react to the natural light cycle, are being asked to relate to an artificial environment. The consequence is that the body’s internal systems are not able to match our behaviour with our environment.

The system that is most immediately affected is the ‘body clock’ controlled by the pineal gland. Disturbance in this aspect of our lives results in poor and disturbed sleep patterns which can, in turn, lead to psychological problems such as stress and attention deficit, and physical risks such as diabetes, obesity and heart disease.

The presence of blue wavelengths within the ambient light spectrum helps to suppress the effect of the pineal gland, ‘fooling’ the brain into thinking that it’s safe for us to go on working, when we should be slowing down for the evening and preparing for a good night’s sleep.

Human-centric lighting systems have always had, at their core, the ability to reduce blue content in white light by shifting the ambient colour spectrum from ‘daylight’ to a comfortable warm light as we come to the end of the working day. Lighting levels (illuminance) are also adjustable across the working day for the same reason – always looking to mimic external conditions.

 

Lighting control

There can be no human-centric lighting without dynamic lighting control. Early installations left the control of human-centric lighting in the hands of room occupants. In most cases, there was no discernible improvement in wellbeing – mainly because no one could agree on what the lighting should be.

The latest thinking on human-centric lighting schemes is that the core lighting should be set according to a set pattern. That is not a universal pattern, though we can acknowledge that there is a general working pattern into which a scheme would fit easily. But part of the bespoke nature of this kind of lighting means that the light pattern MUST be agreed between the lighting designer and the end user.

There are other ways of providing a personal lighting environment. Acting beneath the core environmental lighting should be a layer of localised or personal illumination. This can be operated at a work-group level, relying on decision-making by a small number of people, or personal task lighting at a single workstation.

 

More reading

Human-centric lighting is still a developing technology. The physical equipment to achieve a positive environment is all available, but it’s worth investing time to understand where the overall human-centric lighting strategy is heading. The WELL Building Standard has been published by the International WELL Building Institute. The latest edition, WELL v2, identifies 10 design concepts for a healthful environment: air, water, nourishment, light, movement, thermal comfort, sound, materials, mind, community.

 

In WELL v2, lighting has an effect beyond its own concept and has a role to play in aspects such as movement, which encourages building occupants to engage in physical activity (anything from dedicated exercise spaces to more attractive staircases), and mind, which promotes de-stressing initiatives such as breakout spaces. These conceptual initiatives call for more exciting lighting solutions within our workspaces, meeting the fundamental needs of building occupants.

You can read more about Tamlite’s approach to human-centric lighting here.