How Circadian Lighting Can Work in a Treatment Rooms
Circadian is a measurable way to support physiology in rooms where people lie still for long periods while therapists concentrate on fine motor tasks. The science is clear that light reaching the eye does more than help us see. It entrains the body clock, shifts alertness, and alters sleep pressure through intrinsically photosensitive retinal ganglion cells that respond most strongly to short-wavelength light. The international CIE S 026 standard now lets designers specify these non-visual effects using melanopic metrics that sit alongside familiar lux, glare and colour rendering values.
For daytime work, the most widely cited benchmark is a minimum 250 lux melanopic EDI at the eye, measured on the vertical plane about 1.2 m above the floor. In the evening, the recommendation drops to no more than 10 lux melanopic EDI to protect evening wind-down and melatonin. For sleep environments it is 1 lux. These thresholds come from a 2022 expert consensus published in PLOS Biology and are echoed by CIE technical notes and WELL’s circadian feature. In practice, many clinics target a softer evening limit of ≤50 melanopic lux when clients are not sleeping but should still relax.
Task visibility still matters. European guidance for healthcare spaces points to 500 lux photopic for general dermatology and treatment rooms, and up to 1000 lux for examination tasks, with glare kept to UGR ≤19 and high colour rendering for accurate skin assessment. Use these as the visual baseline, then overlay the melanopic targets above to deliver both comfort and circadian support.
Why it helps clients relax
Dynamic, blue-depleted evenings support earlier sleep timing and calmer physiology. In a cardiology unit, a programmable system that delivered blue-enriched light by day and blue-depleted light in the evening advanced patients’ rest–activity phase by 160 minutes and increased overnight sleep by 66 minutes compared with standard lighting. Patients also reported higher morning and evening alertness. The same principles translate to spa recovery rooms and late appointments where clients benefit from a gentle wind-down after treatment.
Short-wavelength, higher melanopic light acutely boosts alertness and vigilance. In a workplace trial, moving from standard 4000 K, 43 lux to blue-enriched, higher intensity light that raised melanopic illuminance 4.5-fold improved night-shift alertness and psychomotor reaction time. Even sub-100 melanopic lux can yield more than half of the maximum alerting effect, which is useful for fine work without creating glare. For day clinics this means giving staff a reliable melanopic “dose” while shielding reclining clients from harsher spectra.
Putting it into a treatment room
Layer the light by role and by time.
Base layer for clients: indirect ceiling or wall wash at 300 to 4000 K depending on time of day. Aim for ≤50 melanopic lux at the client’s eye in the chair during pre- and post-treatment calming. Keep UGR low with diffuse optics.
Task layer for therapists: high CRI task light positioned to avoid client eye line. Target 500 to 1000 lux photopic on the task plane with ≥250 melanopic EDI at therapist eye level in daytime. Use narrow beam task heads or under-shelf lights so the therapist gets melanopic stimulus while the client does not.
Evening scene: warm spectrum 2700 to 3000 K, dimmed so therapist eye level stays alert enough for safety but client vertical melanopic stays low. Use amber night lights for circulation and avoid cool accent lighting near the couch.
Specify tunable white luminaires with published spectral power distribution and a melanopic daylight efficacy ratio so you can predict melanopic EDI at different dim levels. Day scenes should push melanopic DER up; evening scenes should pull it down without falling below visual task lux for safety.
Circadian metrics are measured on the vertical plane at eye height, not on the treatment bed. Place sensors or meter at therapist head height where they stand, and at the client’s head on the couch. Daylight helps you meet daytime targets, but add shading to avoid uncontrolled morning spikes on the client side.
Pick optics that keep UGR ≤19 in the therapist’s field of view and maintain CRI 90 for accurate skin tone and erythema assessment. Keep reflective finishes matte and use neutral wall colours to avoid spectral distortions.
Automate the day.
Program three scenes on a scheduler:
Morning/day work: high melanopic, task-forward.
Treatment: task light on, base light moderate, client vertical melanopic trimmed.
Evening wind-down: warm, dim, blue-depleted, pathway lights only. Evidence from hospitals shows that time-varying spectra and intensity can shift phase and improve perceived alertness without compromising nursing tasks, which maps well to therapist workflows.
Clinics that layer spectrum and intensity by task and time can create rooms that calm clients while keeping therapists alert and accurate. The research base and the standards now give you the numbers to design with confidence.
