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We are delighted to welcome ClearLight as a new participant in our Group. At ClearLight, they believe that the way we approach lighting is fundamentally flawed. For decades, lighting has been designed around standards, efficiency, and cost reduction, while the human perspective has largely been overlooked. Good lighting, however, does far more than simply illuminate a space. It affects our biology, our natural rhythms, and our overall wellbeing. It influences how we feel, how we perform, and how we recover. “In the Good Light Group, we have found like-minded professionals who share this belief. Together, we are working towards a necessary paradigm shift: from lighting designed for standards and energy efficiency to lighting designed for people,” says Maurijn, co-founder of ClearLight. More info about ClearLight

Light is more than something you see. When it enters your eyes, it reaches parts of your brain that regulate your sleep, your mood, your alertness, and your long-term health. This happens every time you step outside, sit under a lamp, or look at a screen, whether you notice it or not. And the pattern of light you live in, bright or dim, day or night, shapes how well your body works. How light shapes your body clock Every cell in your body follows a roughly 24-hour rhythm. This internal clock controls when you feel sleepy, when you feel awake, when hormones are released, and when your body temperature rises and falls. For the clock to work properly, it needs to stay aligned with the world outside. Light is the main signal that keeps it on track. Specialised cells at the back of your eye detect light and send signals to the brain regions that run this clock. This happens whether you notice the light or not. Bright light in the morning tells your body it is daytime: you wake up properly, you feel alert, and your clock gets set for the day ahead. Low light in the evening and darkness at night tell your body it is time to wind down, release the sleep hormone melatonin, and rest. The problem is that modern life flips this pattern. Most of us spend our days indoors, where light levels are far too low to give the body a strong daytime signal. In the evening, we surround ourselves with bright indoor lighting and screens, which the body reads as continued daylight. Days are too dim, nights are too bright, and the internal clock drifts out of sync. When that happens, sleep gets worse. Mood and alertness suffer. Over time, the mismatch can affect physical health too. The good news is that light exposure is something you can adjust. You do not need supplements or special products. A few simple behavioural changes are enough to give your body the light signals it expects. Five practical tips Get outside in the morning Even on a cloudy winter day, outdoor light is far brighter than a typical indoor environment. Spending time outside, especially in the morning, is the most reliable way to give your body the light signal it needs. Standard office lighting is usually not enough on its own. Sitting near a window helps, but going outside is better. Sit near a window when you are indoors Most of us cannot spend the whole day outside. Where you sit indoors makes a real difference. Natural light through a window is still much brighter than most artificial lighting, and the closer you are to the window, the more light reaches your eyes. Position your desk or your usual seat to face a window if you can. Dim your lights two to three hours before bed Bright light in the evening tells your body it is still daytime. It delays your internal clock and suppresses melatonin, which makes it harder to fall asleep. Dim your overhead lights, switch to lower lamps, and avoid bright bathroom lights right before bed. The contrast between a bright day and a dim evening is what your body is looking for. Keep screens dim in the evening Phones, tablets, and laptops are bright. The simplest thing you can do is turn the brightness down. Reducing screen brightness matters more than switching to a warmer colour setting. Better still, put screens away in the hour before sleep and let the room around you be dim. Sleep in darkness Even low light levels during sleep can affect sleep quality and the timing of your body clock. Use blackout curtains if outside light reaches your bedroom. Cover or remove glowing electronics. If you need a light during the night, keep it as dim as possible. So light is a powerful signal for your body. Bright days, dim evenings, and dark nights are what your biology expects. Getting that pattern right supports your sleep, your mood, and your long-term health, and the most effective steps are behavioural and free.

Jeroen Bosch Hospital (JBZ) in Den Bosch, the Netherlands, has reported encouraging early results from a new night-shift system called a “chrono-schedule”. In a pilot study, nurses working under the new system said they felt less exhausted after night shifts, had less difficulty staying awake, and recovered more quickly afterwards. Photo by Amir Arabshahi on Unsplash Instead of working a full night shift, staff worked shorter shifts from 8.00 pm to 4.00 am or from 4.00 am to 12.00 pm, with a daytime shift in between. This meant they could still sleep during part of the night. The trial also found fewer stomach and bowel complaints, and many nurses said they felt recovered within a day rather than needing two or three days. Doctors involved in the project say the new system appears to fit better with the body’s natural rhythm. However, it may not suit everyone, as it can affect social life and evening activities. Because some of the staff do not want to go back to the old schedule, the hospital will continue using the chrono-schedule for now and will carry out a follow-up study in the summer before deciding whether to introduce it permanently.

Sleep is fundamental to our health, performance, and wellbeing — yet it is increasingly disrupted by our everyday’s actions and the way we design and light our buildings. This CIBSE-approved CPD course explores the science of sleep, our internal body clock, and how integrative lighting design can actively support healthier sleep–wake rhythms. Photo by Gregory Pappas on unsplash Understanding sleep: more than just “switching off” A clear overview of what sleep actually is, breaking it down into its main stages: Stage 1 – Drowsy sleep (5–10 minutes):The transition between wakefulness and sleep. Muscle relaxation begins, eyes roll slowly, and we remain sensitive to surrounding noise. Stage 2 – Light sleep (10–25 minutes):Brain activity and heart rate slow, body temperature drops, and we can still be woken easily. Stage 3 – Deep sleep (20–40 minutes):The most restorative phase of sleep. We become largely insensitive to noise, slow brain waves dominate, and the body focuses on physical recovery, tissue repair, and growth hormone release. REM sleep – Paradoxical sleep (20–40 minutes):Characterised by rapid eye movements, vivid dreaming, and muscle relaxation. This stage plays a critical role in memory consolidation and emotional processing. Understanding these stages, how they are organised in stages and their connections helps explain why both sleep quantity and quality are vital for health.   Our internal clock and the role of light A key part of the course focuses on the body’s internal clock, or circadian rhythm. This clock is primarily synchronised by the external 24-hour light–dark cycle, known as a photic zeitgeber. Daylight entering the eyes sends signals to the brain’s master clock — the suprachiasmatic nucleus (SCN) — which regulates bodily functions and hormone production throughout the day. In addition, non-photic zeitgebers such as sleep routines, physical activity, social interaction, and meal timing also influence our rhythms via peripheral oscillators.   Why indoor lighting often works against us Modern indoor environments frequently provide lighting that is too dim during the day and too bright in the evening. This mismatch can undermine circadian entrainment, disrupt sleep quality, and negatively affect health and alertness. The course introduces melanopic equivalent daylight illuminance (m-EDI lux) — a metric that quantifies how light affects the melanopsin system in the eye, which is crucial for circadian regulation.   What “good light” looks like Based on current research, the course outlines practical m-EDI* targets: Daytime: Minimum 250 m-EDI lux (vertical) to support alertness and circadian entrainment Evening (starting at least three hours before bedtime): Maximum 10 m-EDI lux (vertical) to allow the body to prepare for sleep Sleep environment: As dark as possible, with a maximum of 1 m-EDI lux (vertical) *The m-EDI lux unit is defined in the CPD course .   Integrative lighting design in practice The CPD course introduces Integrative Lighting Design, which considers both: Visual needs (seeing and task performance) Non-visual effects (circadian regulation, sleep, and wellbeing) Through a structured design process and a real-world case study, the course demonstrates how lighting solutions can successfully support both visual comfort and biological needs.   Key takeaways By the end of the course, participants will understand that: Sleep is crucial for long-term health and wellbeing Light does far more than enable vision — it regulates our internal clock Poor indoor lighting can disrupt sleep and circadian rhythms, and affect our health Integrative lighting design can support both visual and circadian needs Well-designed projects show this approach is achievable in practice This CPD provides valuable insight for anyone involved in building design, lighting, or occupant wellbeing — offering practical knowledge to help create healthier indoor environments through better lighting.   Follow the CPD course here , a certificate is available if needed for your professional institution, after completing some questions on the course material.

Sleep doesn’t start when your head hits the pillow, it begins hours earlier with the signals you send your brain. One of the most important signals is light. To support deep, restful sleep, it’s recommended to keep light levels below 10 lux starting three hours before bedtime. Photo by Giorgio Trovato on Unsplash   How Light Affects Your Sleep Your brain uses light to decide whether it’s time to be awake or asleep. Bright light in the evening, especially artificial lighting and screens, can delay the release of hormones that helps you fall asleep. Even moderate indoor lighting can confuse your brain clock and make it harder to wind down. Keeping light levels very low in the evening tells your body that night has arrived.   Dim the Lights As bedtime approaches, gradually reduce the brightness in your home. Use: Dimmable lights Low-watt, warm-coloured lamps Indirect lighting instead of overhead lights The goal is a soft, calm environment that allows your eyes to relax.   Close the Curtains Outdoor light, from streetlights, cars, or buildings, can easily push light levels above what your brain considers “night.” Closing curtains or blinds helps block unwanted light and creates a darker, more sleep-friendly space.   Avoid Bright Screens Phones, tablets, TVs, and laptops emit light that strongly signals “daytime” to your brain. In the final three hours before bed: Avoid unnecessary screen use Lower screen brightness as much as possible Choose non-screen activities like reading Set your screen devices to night mode   Create a gentle transition to sleep By keeping light levels below 10 lux for the three hours before bedtime, your brain is going to helping you fall asleep faster and sleep more deeply.

Last week, Jan Denneman had the opportunity to speak at Light + Building in Frankfurt as Chair of the Good Light Group. What continues to strike him is this: we spend around 90% of our time indoors, yet the light around us is fundamentally misaligned with our biology. The impact is not subtle. It shows up in poor sleep, low energy, reduced wellbeing, and long-term health risks. And still, we treat this as normal. The reality is simple. During the day, most indoor environments are far too dim to properly stimulate our circadian system. In the evening, they are often too bright, sending the wrong signals to our body when it should be preparing for rest. On top of that, artificial light differs significantly from natural daylight in its spectral composition. We are, quite literally, designing light against human biology. Science has already given us clear guidance. During the day, we need around 500 to 1,000 lux at eye level to properly stimulate our circadian system. In the evening, light levels should drop below 20 lux, and at night to almost complete darkness. Yet in practice, most people receive only a fraction of the light they need during the day, unless they are sitting right next to a window. The result is a continuous disruption of our internal clock. The consequences are significant and well documented. Light affects how we sleep, how we feel, how we perform, and how healthy we are over time. If we improved sleep alone through better lighting, the economic value would be enormous. So why is this not happening at scale? Because we are still optimising for the wrong thing. The 3–30–300 rule makes this painfully clear. For every €3 spent on energy and €30 on the building, organisations spend around €300 on the people inside (per 0.1m² per year). Yet lighting decisions are still largely driven by saving a fraction of the €3, while ignoring the much larger impact on the €300. This is where the real opportunity lies. Not in squeezing out another percentage of energy savings, but in improving human health, wellbeing, and performance through better light. Indoor lighting should not be treated as a purely technical or efficiency-driven system. It is a health intervention hiding in plain sight. That means this is not just a topic for the lighting industry. It is a responsibility across the entire ecosystem shaping our indoor environments, from designers and architects to installers, building owners and investors, and not least employers who care about the wellbeing of their people. In this short clip, Jan explains why it is time to rethink how we design light indoors, and why the cost of inaction is far greater than we tend to assume. Watch video

We’ve organised our 24th Good Light Group meeting.   The topics included: 1. Jan Denneman - Good Light Group news 2. Lawrence Lin – Good Light Group Asia 3. Kevan Shaw – The aging eye Photo by Andres Sanz on Unsplash Missed the Good Light Group Meeting?   Watch the presentions online here:   Good Light Group news - Jan Denneman The aging eye -  Kevan Shaw

Spending time outdoors is ideal, but many of us still spend large portions of the day inside. When natural daylight is limited, optimizing your indoor light environment becomes essential for maintaining energy, focus, and a healthy daily rhythm. These two simple steps can make a big difference.      Photo by Surface on Unsplash     Step 2: Stay within one meter of a window When you’re indoors, your proximity to natural light matters more than you might think. Light intensity drops dramatically the farther you move away from a window. By staying within one meter of a window, you allow your eyes to receive significantly more daylight, even on cloudy days. Working, reading, or relaxing near a window helps: Support your circadian rhythm Improve alertness and concentration Reduce eye strain compared to dim indoor spaces   If possible, position your desk, dining table, or favourite chair close to a window. Even indirect daylight is far more powerful and biologically effective than most indoor lighting.   Step 3: Use high-quality electric lighting during the day When natural daylight isn’t enough, especially in windowless rooms or when your desk is more than a meter away from a window, high-quality electric lighting is essential. Poor or insufficient lighting can leave your body in a “low-energy” state, even if you feel mentally busy. To properly support daytime alertness:Ensure your eyes receive at least 500 lux during the daytime Use bright, evenly distributed lighting rather than a single dim lamp Choose lighting designed for daytime use that compensates for the lack of daylight Reaching 500 lux at eye level helps signal to your brain that it’s daytime, supporting focus, productivity, and mood. This is especially important if you work indoors for long hours.   Creating a light-smart indoor environment Combining natural and artificial light is the key: Sit close to windows whenever possible Supplement with high-quality electric lighting when daylight is lacking Prioritize brightness during the day and reduce it in the evening By managing your indoor light exposure intentionally, you help your body stay Aligned with its natural rhythms—leading to better energy during the day and better sleep at night. Good lighting isn’t just about seeing better. It’s about living better, even indoors.

We are very happy to welcome it doens Lighting to our group! It does Lighting is an independent, qualified, and evidence-led company with nearly 40 years of experience. They get to the root of what light means and how it acts as nutrition for the body’s cells, and they are highly experienced in designing healthy lighting schemes. “I was pleased to accept the invitation to join the Good Light Group as a Scientific Advisor. The group brings together an international cohort of respected researchers and professionals who share a commitment to advancing the science of light and its impact on human health.   My involvement is voluntary, and I joined because the organisation’s values, ethics, and science-based approach strongly align with my own work in light and health. The Good Light Group is helping to promote a clearer understanding of what good light means for healthier, more resilient lives, and I am delighted to contribute to that mission.” Lorraine Calcott Director and Principal Designer it does Lighting

In our busy, screen-filled lives, it’s easy to spend most of the day indoors. But making time to step outside, particularly in the morning, can have a huge impact on your overall health and well-being. In fact, scientists recommend spending at least 2 hours outside during the day, with a good portion of that time in the morning if possible. Photo by cal gao  on Unsplash   The power of morning light Morning sunlight plays a vital role in setting your body’s brain clock, also known as your circadian rhythm. Getting natural light early in the day helps signal to your brain that it’s time to wake up and be alert. This can lead to better focus, improved mood, and even better sleep at night.   Boost your mental well-being Time spent outdoors has been shown to reduce stress, anxiety, and mental fatigue. Starting your day outside, whether it’s a walk, stretching, or simply enjoying your coffee, can set a positive tone for the hours ahead.   Easy ways to get your 2 hours outside Spending two hours outdoors doesn’t have to happen all at once. You can break it up throughout the day: Take a morning walk or commute on foot Eat lunch outside or in a park Schedule outdoor breaks instead of indoor ones Do phone calls or meetings while walking outside or at least close to a window Make It a Daily Habit Think of outdoor time as a non-negotiable part of your day, just like eating or sleeping. By prioritizing at least 2 hours outside each day, especially in the morning, you’re investing in better energy, clearer thinking, and long-term health. Sometimes, the simplest habits make the biggest difference. So tomorrow morning, step outside, take a deep breath, and let the day begin naturally.

A blog by Ivo Habets “Natural daylight during office hours improves glucose control and whole-body substrate metabolism” The circadian timing system regulates many processes in the human body. While it is best known for controlling our sleep–wake cycle, metabolism also follows a strong daily rhythm. This includes processes such as glucose regulation, insulin sensitivity, and substrate use, which vary across the day in a coordinated manner. The main entrainment signal for the circadian rhythm is natural light, rich in blue-white light, detected by retinal cells in our eyes. Nowadays, however, much of our daytime is spent indoors under constant artificial lighting that differs substantially from natural daylight in both intensity and spectral composition. It is also known that people with metabolic diseases such as type 2 diabetes show disturbances in their circadian metabolic rhythms. Until now, it has been unknown how light exposure affects their main circadian rhythm and the regulation of metabolism as a consequence. A recent study by Harmsen et al. investigated the effects of daytime light exposure on metabolic outcomes in people with type 2 diabetes. Participants were exposed to two different lighting conditions for five consecutive days. In one condition, they were exposed only to artificial indoor light. In the other condition, they were exposed to natural daylight behind a window between 8:00 and 17:00. Other factors, such as meals and daily routines, were controlled. The results showed that glucose control was better during the natural daylight condition, as indicated by more time spent within normal glucose levels when participants were in the natural daylight condition. However, there was no difference in the mean glucose levels between the two conditions. Nevertheless, this improvement in glucose stability is clinically meaningful, as fluctuations in glucose are associated with metabolic complications. In addition, substrate use was assessed at multiple time points at the end of the week. Participants relied more on fat metabolism in the natural daylight condition compared to the artificial light condition. This effect was most pronounced when the intensity of natural light was brightest. These findings suggest that daylight may strengthen the daily rhythm of macronutrient utilisation. During the last evening of the week, melatonin levels were also measured. While the onset of melatonin secretion did not occur earlier, melatonin concentrations after onset were higher in the natural daylight condition. This study demonstrates that metabolism is influenced by the circadian system and that natural light acts as a key regulator. Importantly, natural daylight exposure should not be viewed as a treatment or cure for metabolic disease; rather, it can support circadian alignment through daytime light exposure and therefore plays a valuable supportive role in improving disrupted metabolic rhythms. Read the full article here

A blog post by Dr. Aida Farshadi For millions of years, humans lived under the full spectrum of sunlight. Our physiology evolved not just with visible light, but also with near-infrared light (NIR), an invisible wavelength that makes up nearly half of the sun's energy reaching Earth. Photo by Todd Rhines  on Unsplash What is near-infrared light and why we're missing it? Near-infrared sits just beyond the red end of the visible spectrum, in the 700–1100 nm wavelength range. Unlike shorter wavelengths that stop at the skin surface, NIR penetrates centimeters into the body, reaching muscles, blood vessels, and the mitochondria within those deeper tissues. Think of mitochondria as tiny batteries inside our cells. Research shows that NIR light helps recharge these batteries, boosting cellular energy while also improving blood flow. These aren't exotic laboratory effects; they appear to be part of how our bodies evolved to interact with sunlight. Here's the challenge: modern life has effectively removed NIR from our daily light exposure. Outdoors, sunlight delivers substantial NIR irradiance to our skin, in the range of tens to hundreds of milliwatts per square centimeter. But indoors? Architectural glass blocks most solar NIR. And while incandescent bulbs and candles do emit some infrared, their intensity is one to two orders of magnitude lower than natural sunlight. This matters because NIR effects are dose-dependent. Below a certain threshold, there is no meaningful biological response; just negligible background exposure. Simply having "some" infrared in a light source is not enough; the irradiance must approach levels comparable to what the sun provides. Most indoor environments fall far short of this. This lack of NIR may contribute to common complaints of modern indoor life: fatigue, poor sleep, reduced alertness, and slower recovery. While definitive causal links are still under investigation, the emerging picture suggests that NIR is not a luxury; it's closer to an environmental nutrient we've unknowingly removed from our daily lives. What can we do? The simplest solution remains: spend more time outdoors. Even on a cloudy day, natural daylight delivers far more NIR than any indoor environment. For those of us who spend most of our time inside, the future may include purpose-built NIR lighting: calibrated sources designed to restore this missing part of the solar spectrum. Not to replace sunlight, but to bring back what modern architecture has filtered out. And there's more to explore. We know that blue light entrains our circadian system, but in nature we never receive blue light in isolation; it always arrives alongside the full spectrum, including NIR. Understanding how these wavelengths might work together could open new directions in light and health research. Good light isn't just about brightness or colour. It's about the full spectrum, including the part we cannot see. References: Hamblin MR. Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophysics . 2017;4:337–361. Avci P, Gupta A, Sadasivam M, et al. Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring. Seminars in Cutaneous Medicine and Surgery . 2013;32:41–52. Jeffrey G, et al. LED lighting undermines human visual performance unless supplemented by wider spectra like daylight. Nature Scientific Reports . 2026; 16:3061.