Circadian lighting—also called human-centric lighting or biologically effective lighting—has been promoted heavily in recent years. The promise is compelling: lighting that improves alertness, mood, sleep quality, and overall wellbeing.

But what does the evidence actually show? And what should facility managers and building owners realistically expect?

The Science in Brief

Our bodies have internal clocks (circadian rhythms) that regulate sleep-wake cycles, hormone release, and many physiological processes. Light is the primary environmental signal that synchronises these clocks.

Key biological points:

• Specialised cells in the eye (melanopsin-containing retinal ganglion cells) detect light for circadian purposes
• These cells are most sensitive to blue-enriched light (around 480nm wavelength)
• Bright light exposure during daytime supports alertness and synchronises circadian timing
• Low light in the evening allows melatonin production and sleep preparation
• Disrupted circadian rhythms are associated with poor sleep, mood issues, and various health problems

The biology is real. The question is whether commercial lighting systems can meaningfully influence these processes.

What “Circadian Lighting” Means in Practice

Commercial circadian lighting typically involves:

Intensity Variation

Higher light levels during the day (500+ lux at the eye), lower levels in evening. This mimics natural daylight patterns.

Colour Temperature Shifts

Cooler, blue-enriched light (5000-6500K) during daytime hours. Warmer, blue-reduced light (2700-3000K) in evening. This shifts the spectrum to align with circadian sensitivity.

Timing Control

Automated transitions aligned with the body’s natural rhythm, typically with bright/cool light in the morning, sustained through midday, then transitioning to warm/dim in late afternoon and evening.

What the Research Shows

Strong Evidence

Healthcare and residential aged care: Multiple studies show benefits in controlled environments with vulnerable populations. Dementia patients, hospital inpatients, and elderly residential care residents show improvements in sleep quality and behavioural outcomes from circadian-aligned lighting.

Shift work settings: Evidence supports benefits for workers with disrupted schedules—night shift workers, control room operators, healthcare workers.

Seasonal Affective Disorder: Bright light therapy is an established treatment. The circadian mechanisms are well understood.

Moderate Evidence

Office alertness: Some studies show improved subjective alertness and reduced afternoon fatigue with higher daytime light levels and cooler colour temperatures.

Sleep quality in office workers: Some evidence that daytime light exposure in offices correlates with better sleep at night. Whether this is from the lighting system or other factors (like window access) is less clear.

Weak or Mixed Evidence

Productivity gains: Claims of measurable productivity improvement from circadian lighting are not well supported. Studies are inconsistent and often industry-funded.

General wellbeing in typical offices: Evidence for meaningful wellbeing improvements in already-healthy office workers from circadian lighting changes is limited.

Cognitive performance: Claims of improved cognition and decision-making are not reliably demonstrated.

The Reality Check

Several factors complicate circadian lighting in commercial buildings:

Exposure Levels

To influence circadian response, light needs to reach the eye at adequate intensity. In a typical office:

• People don’t look at the ceiling
• Screens emit light at the eye (potentially overpowering ceiling lighting)
• Personal lighting preferences vary dramatically
• Window access may dominate indoor lighting effects

Achieving 500+ lux at eye level consistently throughout a workday is difficult without specific design attention.

Individual Variation

Circadian systems vary between individuals:

• Chronotype (morning vs evening preference) affects optimal timing
• Age affects light sensitivity (older people need more light)
• Individual health conditions influence circadian function
• Previous light exposure affects current responsiveness

One-size-fits-all schedules may not suit everyone.

Competing Factors

Light is one circadian input among many:

• Sleep schedules and habits
• Caffeine and other substances
• Exercise timing
• Social and meal schedules
• Screen exposure outside work

Building lighting changes may be overwhelmed by other influences.

Occupant Acceptance

Some people find cool-white light harsh. Some prefer dimmer conditions. Circadian-optimised settings may conflict with user preferences.

If occupants override the system or complain, the theoretical benefits don’t materialise.

Where It Makes Sense

Based on current evidence, circadian lighting investments are most justified in:

Healthcare facilities: Particularly for inpatient areas, aged care, and mental health settings. The evidence is strongest here.

Shift work environments: Control rooms, call centres, manufacturing with rotating shifts. Supporting shift workers’ alertness and sleep is valuable.

High-value office environments: Where attracting and retaining staff matters and the building makes a wellness statement. The benefits may be modest but contribute to overall environment quality.

Educational facilities: Some evidence supports benefits for students, particularly in morning classes.

Where It’s Questionable

Standard commercial offices: For typical 9-5 office workers with window access, the incremental benefit over good conventional lighting is uncertain.

Budget-constrained projects: The premium for tunable white systems may not be justified if the budget would otherwise compromise basic lighting quality.

Spaces with high turnover: Retail, hospitality, public spaces where occupants are present briefly. Circadian effects require sustained exposure.

Implementing Circadian Lighting

If you proceed with circadian lighting:

Design for Exposure

The ceiling light has to reach the eye. Consider:

• Vertical illuminance on work surfaces
• Indirect lighting on walls and ceilings for higher room brightness
• Task lighting at the desk providing appropriate levels
• Careful glare control (glare means people look away from the light)

Keep It Automatic

Don’t rely on occupants to adjust settings. Automatic scheduling based on time of day is essential.

Allow Override

Individuals should be able to adjust their immediate environment. Personal task lighting gives flexibility.

Set Realistic Expectations

Don’t promise productivity gains or health improvements. Promise better lighting that supports natural rhythms. Let benefits emerge rather than claiming them.

Consider the Whole Building

Circadian lighting is most meaningful when the whole building supports it—not just workstations but also meeting rooms, break areas, and circulation.

The Technology Maturity Question

Tunable white LED technology is mature enough for commercial deployment. Products exist at various price points with reasonable reliability.

What’s less mature is:

• Industry consensus on optimal parameters (how bright? what CCT? what timing?)
• Evidence base for commercial (non-clinical) applications
• Integration with personal devices and schedules
• Long-term studies of real-world implementation

The technology works. The application knowledge is still developing.

Cost Considerations

Circadian-capable systems cost more:

Tunable white fittings: 20-50% premium over fixed CCT fittings

Controls infrastructure: More sophisticated control system required

Commissioning: Programming schedules and transitions takes time

Ongoing management: Schedules may need adjustment over time

The payback is hard to quantify because the benefits are soft (wellbeing, alertness) rather than hard (energy savings).

Some clients fund circadian lighting from wellness or HR budgets rather than facilities budgets. The framing affects approval paths.

Looking Ahead

Circadian lighting will become more common as:

• Evidence accumulates (or doesn’t)
• Costs reduce as technology matures
• Wellness building certifications (WELL, Fitwel) drive adoption
• Occupant expectations evolve

For now, approach it with informed scepticism. The biology is real. The commercial building application is still developing. Invest where evidence supports it; be cautious about claims that outrun the research.

James Thornton has been working in commercial lighting for 18 years and is based in Australia.