Moaath Al-Bukaai
For thousands of years, humans lived in sync with nature’s rhythm — including our own biological clock, the circadian rhythm, which regulates melatonin, the hormone responsible for controlling sleep and wakefulness.
Melatonin — the sleep hormone — is released at sunset to help the body relax and prepare for sleep. It’s what lets us fall into deep sleep, so the body can rebuild itself overnight and get us ready for a new day. This release is controlled by special sensors in the eye, placed there for exactly this purpose: ipRGCs. These sensors read the intensity and color of light. When light gets stronger and shifts from yellowish-white to white around midday, they send a signal to stop melatonin production, keeping us alert and giving us the energy to get through the day.
When light fades and shifts from white to reddish-white at sunset, the sensors send the opposite signal — resume melatonin production — easing the body into a relaxed state before sleep. Research published in PNAS confirms this mechanism: these light-sensitive cells drive melatonin suppression most strongly in the blue portion of the spectrum, around 460nm.
All of this ran on the sun’s schedule, naturally, until one great invention changed everything: artificial light. It was a genuine breakthrough — it gave us our day back and pushed productivity to levels we’d never seen. But it came at a cost. The sensors that control our melatonin lost their reference point. They now sense light all day long, with no real change in intensity or color, so melatonin production has become very weak. How are we supposed to fall asleep right after moving from bright, unchanging light straight into bed? We lost the transition — afternoon into sunset into evening — because the light around us never changes. That transition used to reset our biological clock every single day. A 2019 review in the Journal of Biophotonics describes this same disruption at a population level — modern indoor life delivers a spectrum and intensity of light our biology never evolved to handle. Now, the consequences are serious:
- Sleep disorders and recurring insomnia
- Fatigue and drowsiness during the day
- Symptoms of depression and sharp mood swings
- Poor concentration
- Bodily disturbances, including a weakened metabolism
These problems have gotten measurably worse in recent years — offices blasting bright white light from morning to evening to chase productivity, living rooms lit with the same harsh glare all day, bedrooms with lighting nobody ever actually designed.
The Fix: Human-Centric Lighting
The human mind doesn’t just invent problems — it invents ways out of them too. Which brings us to today’s topic: Human-Centric Lighting, or HCL.
HCL controls light manually or automatically, adjusting both intensity and color. Modern light sources are no longer fixed at one color — they can shift from a reddish-white around 1800K to a cool, blueish-white around 6500K. They can also dim to levels we never used to have access to, down to as low as 0.1%. Tunable-white DALI-2 drivers with this exact range are already commercially available — this isn’t a lab concept, it’s installable today.
To get there, you need three things in place:
- A light source that supports intensity control (proper dimming)
- A light source that supports color-changing, by blending two different color-temperature chips
- A control protocol that can actually drive both
None of that matters, though, without a system to send the light the color and intensity it needs. That’s where protocols like DALI, Zigbee, and Matter come in — supported by manufacturers like Vimar, Jung, and Lunatone. Through their switches, you can control light color and intensity manually, or automate it entirely by linking the light in your home to the sun’s actual position, in real time.
You and your children have a right over you. Beautiful finishes aren’t enough on their own — a system that actively protects the health of the people living in a space deserves to be one of the top priorities, not an afterthought.
A Client Who Couldn't Go Back
I remember a villa owner in Bahrain who took his lighting seriously and specified high-end products — Collingwood Lighting and Aurora Lighting, on a Vimar control system. He said something to me I still think about:
“Moaath, I have a problem with you. After properly studying the lighting in my own house, I can’t sit in my sister’s house anymore. My body’s become sensitive to bad lighting.”
What he meant was simple: he’d found a kind of comfort he’d never had before, and going back to old-style, static lighting now genuinely gives him a headache.
What This Means for You
If you’re building or renovating, here’s what to actually ask for — not as a luxury add-on, but as something decided at the design stage, before the wiring goes in:
- Real dimming, not marketing dimming. Ask for drivers that dim smoothly down toward 0.1%, not the jumpy 10%-steps you get from cheap dimmers. That’s the difference between a “dim” room and an actually relaxing one.
- True tunable white, not a single fixed color temperature. Your bedroom and living room should be able to shift from warm (around 1800–2700K) in the evening to neutral or cool during the day — not stay locked on one setting year-round.
- A real control protocol — DALI-2, Zigbee, or Matter — not just a basic wall dimmer. This is what lets the system actually talk to the lighting instead of just switching it on and off.
- Automation tied to time of day, not just manual scenes you have to remember to change. The whole point of HCL is that it should follow the sun without you thinking about it.
- Match the room to its purpose: warm, low light in bedrooms and living spaces in the evening; neutral white in kitchens and bathrooms; cooler, brighter light in home offices and workspaces.
This isn’t about chasing the newest gadget. It’s about designing a home that actually protects the people living in it — and once you’ve lived with it, like my client in Bahrain, it’s hard to go back.
Further Reading & Sources
Scientific Studies
Spectral sensitivity of human circadian phase resetting and melatonin suppression — PNAS, 2022
The inner clock — Blue light sets the human rhythm — Journal of Biophotonics, 2019
The Circadian Response of Intrinsically Photosensitive Retinal Ganglion Cells — PLOS One
Suppression of Salivary Melatonin Secretion Under Blue Light — PMC / NIH