A human centric lighting vision

Light affects us in different ways; physically, emotionally and biologically. To society, light is imperative and acts as the most powerful regulator of the human day/night rhythm. In the simplest terms, light tells the body to be awake and alert during the daytime which allows us to experience the world around us.

Human beings have evolved to function under daylight, and as we know, this light level changes throughout the day. The adjustment ranges from bright white light to softer warm tones at night. Humans have adapted to this circadian cycle over our 120,000 years of evolution. Andy Taylor, Technical Manager at Light Culture Australia, believes that the exposure to this fluctuating spectral power distribution has resulted in our exquisite sensitivity to natural light.

Nowadays, we spend about 90% of our time indoors; this means our indoor environment becomes paramount for our general health and well-being. Given the human body needs an adequate amount of light at the right intensity and at the right time of day to act as prompts for our internal body clock, indoor lighting conditions need to deliver the light nutrition we need to stay healthy and be productive. For instance, a sunny, outdoor day will provide 10,000 lux, while internal daylight-deprived areas can generally achieve lux levels of around 250 – 500. Andy believes that the recent move from outdoor life to indoor working environments has resulted in an alien landscape. He inherently blames statically lit interiors and the focus in horizontal illuminance in areas where daylight penetration is limited or non-existent. “Illumination power density targets have rendered these spaces gloomy, cave-like and depressive,” he states.

Recent research has uncovered a novel photoreceptor in the eye called the intrinsically photosensitive retinal ganglion cell (ipRGC for short), which reacts in a very different way to the rods and cones. Stimulated by light wavelengths in the blue spectrum, the ipRGC works through the suprachiasmatic nucleus (the body clock) to regulate the secretion or suppression of a neurochemical, called melatonin.

Human Centric Lighting (HCL) is the new buzzword in the lighting profession. This method is the next step in LED design and control to support the human circadian rhythm; enhancing concentration, preventing sleeping disorders and improving our overall well-being.

As HCL mimics the circadian cycle to regulate our natural stimulus correctly, it is imperative for lighting designers to understand how this application of light can impact users’ health, productivity, and overall potential. With a focus on both the visual and non-visual effects of the lighting, HCL not only helps us perform visual tasks but also acts as our internal biological clock.

HCL, when judiciously applied, has been accredited with improvements to productivity, vigilance, error rates, happiness, energy levels, staff retention and health. Andy states that historically speaking, there was limited education around HCL and with the dominance of fluorescent lamps it was challenging to achieve in practice. “With the arrival of LEDs came the ability to control the level of blue stimulus, and further research has revealed more knowledge of its correct application,” he declares. These blue frequencies provide a desirable stimulating effect during the day, however, at night they disrupt the body’s circadian rhythm and disrupt different biological systems. Research shows that emitting more than 2% of blue in a well-lit room at night can disrupt circadian rhythms, suppress melatonin and causes health risks.

HCL has claimed many benefits, including work execution and advances recorded in education facilities; with improved reading performance and mathematical problem-solving. “Even healthcare institutions have seen reduced recuperation times,” comments Andy. With studies showing that automated lighting can comfort and help patients maintain regular sleeping patterns in hospitals, improve mental and emotional conditions while helping to keep medical professionals alert during long shifts.

Lighting design for the circadian system utilises objectives that differ from those typically used in traditional architectural lighting design which requires specific metrics. Andy says there are several metrics which allow us to calculate if the light from a luminaire is good, bad, or just plain ugly. “One is the daylight Equivalent Melanopic Lux metric (as used by the WELL Building Institute), and the other is the Lighting Research Centre proposed Circadian Stimulus (CS) value,” he confirms. Both these figures have a different approach, but both require comprehensive data from the Spectral Power Distribution curve (SPD). Figures arrive at a level of stimulus which can suppress the secretion of melatonin. High suppression is good for the beginning of the day, and low suppression is good for night time. Andy reinforces that the spectrum of the light is not the only factor and we must consider the amount of light, its distribution, timing and duration.

The Well Building Standard (WBS), produced by Delos Living LLC of New York, is a first in that its sole focus is the health and well-being of the occupants of a building. Originally founded on robust principles, its v2 version contains ten concepts: Air, Water, Nourishment, Light, Movement, Thermal Comfort, Sound, Materials, Mind and Community. Each concept is comprised of features with distinct health and well-being benefits.

The WELL Light concept aims to promote exposure to light with a goal to create lighting environments that are optimal for visual, mental and biological health. The concept states that given people spend so much time indoors, insufficient illumination or improper lighting design will disrupt their circadian phase, particularly if paired with inappropriate light exposure at night.

Andy explains that the light concept contains eight features that recognise and reward excellence in lighting practice. Some features are pre-conditions (mandatory), others are optimisations (in which you score points). “Feature L03 covers circadian lighting and uses daylight Equivalent Melanopic Lux (EML) to evaluate the performance of the fixture in the space, arriving at a figure of vertical melanopic illuminance at the eye,” he explains. While feature L05 recognises the geometry of the building in regards to daylight access for the occupants, as well as a view of outside.

V2 communicates the importance of adequate periods of both light and darkness to synchronise the circadian rhythm. As humans are continuously sensitive to light, under normal circumstances, light exposure in the late night/early morning will shift our rhythms forward, whereas exposure in the late afternoon/early night will shift our rhythms back.

WELL presents an opportunity for projects to integrate daylight and electric light to create lighting strategies focussed on health and well-being. As lighting conditions are currently not taking into account the circadian phase, WELL aims to provide environments that reduce this disruption, with the added benefit of improving the occupants’ sleep, mood and productivity.

The WBS has gained traction in the USA, UK and China, and is now also referenced within Australia. Depending on points scored, buildings can attain a certification ranging from Silver (50 points), Gold (60 points), to Platinum (80 points) levels. Andy is a strong supporter of the WELL Building Standard and finds it refreshing to see this type of movement in a time when lighting seems to be dominated by power usage. Although he still has some reservations; “Australia and New Zealand have adopted lower horizontal illumination levels than the rest of the developed world,” he states, which means it will be much harder to achieve the desired vertical illumination levels needed at the eye, for circadian stimulus.

Andy stresses the National Construction Code (NCC) proposal for 2019. He says that the plan calls for such low illumination power density targets, it is unlikely the circadian lighting will be effectively deployable in many circumstances. Andy says that the NCC won’t just make it difficult, they will almost certainly eliminate good practice lighting from Australia. “Further correction factors, in addition to the lighting control factors already in place in J6 (deals with the minimum standards for energy efficient lighting design), need to be added for the application of circadian lighting into the spaces,” he states.

Although there are those non-believers, Andy says there is unchallengeable evidence in proving the health benefits of Human Centric Lighting. “There is an increasing amount of supporting research and new installations globally,” he proclaims.

With the new knowledge we have about the biological effects of light, and at a time we are finding out so much about the non-visual response of the human eye, new applications of illumination have been made possible. With LED sources becoming more efficient and versatile, and with more sophisticated controls, lighting systems now create endless possibilities. “The stars are aligning, and we are about to embark on an exciting new world of lighting for people,” Andy claims.


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