Circadian Lighting – Why does it feel so good?

by JHA Specialist Lighting Team


Reminisce with me for a moment.

Detach your mind from your desktop and send it back to your last great summer holiday. The one where, despite the seasonal chaos of friends, family and too much food, you found yourself shift into satisfying new rhythms of sleep and waking, activity and rest.

How did you feel? In balance or in tune, perhaps? At ease, or like some lost ‘rightness’ was temporarily restored?

While we can credit many of those feelings to a respite from our work, there’s growing evidence that an increased daily exposure to sunlight could contribute to our physiological and emotional wellbeing. That fathomless holiday sleep and inexplicable urge to walk the beach at sunrise might not solely stem from over-consumption and the get-fit-guilt that follows. Rather, they could be signs that spending more time outside is giving your disrupted body clock the cues it needs to re-synchronise. This bodily synchronisation with external cues, especially natural daylight, is called circadian entrainment.

Though the phenomenon has long been known to exist (it is, for example, considered in mission design for astronauts and submariners), we are yet to fully understand its mechanisms. We now know that there are specific non-visual cells in the eye, melanopsin receptors, which respond to blue light around 470nm in wavelength. These receptors influence the activity of the suprachiasmatic nuclei (SCN) in the hypothalamus, which acts as our bodies’ ‘master clock’, regulating chronobiological actions like hormone secretion.

Physiological Performance Curve image usage with kind permission from XAL Holding GmbH / Austria

What’s next for Circadian Lighting?

Scientists are now working to understand the cause-effect links between specific lighting stimuli and their related biological outcomes. For instance, one recent study showed that the amount of amber light in our ‘light history’ (the illumination conditions we’ve experienced in the recent past) influences how well our body clock becomes entrained to melanopic (~470nm blue) light.

This presents lighting designers with a bunch of interesting design questions. Could amber night lighting in an aged care home elevate residents’ circadian entrainment to morning sunlight? If the answer is yes, something as simple as fitting colour filters to existing night lights could prove an affordable, drug-free way to give our seniors better sleep. Talk about a lightbulb moment! Another feature you might be more familiar with is the night time blue light filter on your smartphone. It reduces the amount of melanopic light emitted from the screen, which would otherwise suppress your natural secretion of melatonin – the hormone that tells your body it’s time for sleep.

We’re referring to precisely these sorts of design factors when we drop the phrase ‘circadian lighting’. Variable colour-temperature LEDs and intelligent lighting control systems have given us new tools with which to design for certain biological and emotional outcomes, not just the visual efficacy criteria embodied by our Standards. Benchmarking our designs on biological and emotional criteria is a core philosophy of the nascent Human-Centric Lighting (HCL) movement.

Like any emerging discipline, circadian lighting is exposed to knowledge gaps, conflicting opinions, embryonic standards, inexperienced designers and over-enthusiastic salespeople. A critical eye, the support of trusted technical advisers and a willingness to iterate will give you the best chance of meeting your circadian lighting objectives.

JHA are Circadian Lighting Pioneers

JHA achieved an Australian first on the recent Mark Moran Vaucluse project successfully implementing circadian lighting in an aged care setting. JHA partnered with XAL, an Austrian lighting researcher and manufacturer, to finalise the development of their ‘Recover’ circadian luminaire and provide it to all care home bedrooms.

This was a considerable challenge, especially in securing the timely supply of a product still in R&D. Simple user controls were critical in the success of the lighting scheme, with JHA contributing custom designs for the circadian lighting switchplates. Commissioning the bespoke control system demanded ongoing diligence from an international team, but the result – a reliable installation offering unprecedented visual comfort and resident health – was a welcome reward.

Read more about Mark Moran Vaucluse

Circadian Enlightenment

  • In the absence of daylight cues, our body clock ‘free-runs’, defaulting to a cycle slightly longer than a 24-hour day.
  • Ageing eyes decline markedly in sensitivity, both to ambient light levels and melanopic light. Illumination that is uncomfortably bright for younger people may be ‘just enough’ for our elderly to carry out tasks with confidence and receive circadian cues.
  • Australian standards don’t yet address circadian lighting. The international WELL building certification tool, using its Equivalent Melanopic Lux metric, is probably the best-known attempt to standardise artificial melanopic light exposure. Competing metrics, such as Circadian Stimulus are being tested by researchers and industry.
  • Use of holistic design frameworks, such as HCL, is one of several ways Specialist Lighting designers distinguish ourselves from Electrical Engineers. We include a standards-based lighting engineering within a much broader human and architectural design context.

Image ‘Circadian lighting usage in hospital recovery’ used with kind permission from XAL Holding GmbH / Austria and Croce&WIR Fotostudio

For the remainder of this post we’ll share our views on some circadian lighting questions our clients frequently ask. We hope they help you understand the opportunities circadian lighting might offer your next project.

Q: What are the benefits of circadian lighting and correct circadian entrainment?


A: Generally, research suggests the potential benefits include:

  • Improved quality and quantity of sleep;
  • Improved alertness and cognitive performance;
  • Reduction in dementia-specific sleep and behavioural problems;
  • Reduction in incidence and severity of depression and anxiety, both of which are strongly influenced by sleep.


Q: Which Australian market sectors stand to benefit most from circadian lighting?

A: The Healthcare and Aged Care sectors are top of the pile for two reasons. Firstly, the majority of circadian lighting research to date has targeted these areas, so operators can invest with greater confidence in the science. Secondly, projects in these sectors best fulfil the criteria which we believe underpin a successful circadian lighting scheme.


Q: What are these criteria?

A: If your project gets a ‘yes’ for most of the following questions, we recommend you take a closer look at circadian lighting:

  • Will occupants spend significant durations in a static lighting environment?
  • Are occupants limited in mobility or otherwise prevented from regular access to natural daylight?
  • Is the facility owner-operated?
  • Does occupant health directly impact the facility’s operating costs, or is occupant health a key metric of facility performance?
  • Does the project budget allow for some additional iteration during design and commissioning, as well as an increase in lighting capital cost?
  • Are the specific biological and emotional objectives clear?
  • Does current research adequately describe the lighting parameters required to produce the specific objectives?
  • Is the operator willing to accept some design risk associated with  emergent technologies?
Q: What does it cost?


A: This is tough to answer, as there are design, supply and construction-side elements which scale differently depending on your objectives. It’s safe to say circadian lighting costs more than conventional schemes in almost all cases. As a very rough guide, allow an additional thirty to fifty per cent in your lighting budget for spaces which need circadian lighting. A savvy lighting designer can help you refine this based on the specific needs of your project.