Is Your Home Keeping Your Nervous System Switched On?

Bathroom Lighting

Rethinking light, flicker and darkness in the healthy home

I have always been passionate about lighting from a design perspective because it can completely change how a room looks and feels. More recently, though, as I have learnt more about the nervous system, sleep and our circadian rhythm, I have started looking at lighting in a slightly different way. Rather than simply asking whether a room looks beautiful, I am increasingly interested in how that room, and particularly its lighting, makes the person living in it feel.

A recent conversation with Alison in the Mood Board community really got me thinking about this. She mentioned how much she prefers the old-fashioned incandescent light bulbs and how much she dislikes LED lighting. It sent me down a bit of a rabbit hole because, looking back through history, our relationship with light has changed enormously in a relatively short time.

We now have access to incredibly efficient lighting and can illuminate practically every corner of our homes at any time of the day or night. That is an amazing technological achievement, but I do wonder whether we have gone from not having enough light to perhaps having too much of it, at the wrong time and in the wrong places.

From firelight to permanent daylight

For most of human history, darkness was simply part of life. We had bright natural daylight during the day, followed by sunset, then much dimmer sources such as firelight, candles, and oil lamps. Gas lighting eventually arrived, followed by the incandescent electric bulb and, much later, the LEDs that now dominate our homes.

I am certainly not suggesting that we should return to candles and oil lamps. Combustion lighting had its own problems, including indoor air pollution from particles and combustion products. What I find interesting, though, is the rhythm of light that we have lost.

Historically, people were exposed to very bright natural light during the daytime and relatively dim, warm, localised light after sunset. Many of us now experience almost the opposite. We spend much of the day inside buildings where the light can be relatively weak compared with daylight, and then illuminate our homes brightly until late into the evening.

Our technology has changed enormously, but our biology still responds to light and darkness.

Were the old incandescent bulbs actually better?

This was one question I particularly wanted to understand. Did old incandescent bulbs flicker as well, or did flicker arrive with LED lighting?

The answer is that incandescent bulbs technically did fluctuate, but generally much less dramatically. An incandescent bulb creates light by heating a filament until it glows. Because the filament stays hot as the alternating current changes, its thermal inertia naturally smooths out much of the fluctuation in light output.

LEDs behave very differently because they can respond almost instantly to changes in electrical current. This means the light quality depends heavily on the electronic driver controlling the LED. A high-quality LED with a well-designed driver can produce extremely stable light, while a poor-quality product—or an LED, driver, and dimmer that haven't been properly matched—can produce significant flicker.

That distinction matters because I don't think the message should be that LED lighting is bad. It's more accurate to say that poorly designed LED lighting can be bad lighting, and that we should be much more interested in the quality of what we specify.

Revisiting a light bulb I discussed with its designer

Interestingly, this isn't my first deep dive into the humble light bulb. I interviewed Buster + Punch founder Massimo Buster Minale a couple of times for articles for my blog and magazine, and I remember discussing his Buster Bulb with him. At the time, I was fascinated by it primarily from a design and innovation perspective. Massimo took something as ordinary and established as the light bulb and completely reconsidered how an LED could look and deliver light.

The original Buster Bulb used a patented central light pipe to distribute the LED light, creating both ambient illumination around the bulb and a more focused pool of light beneath it. It was a really interesting example of taking a technology that can sometimes feel quite harsh and treating the light itself as part of the design.

Looking back at those conversations now is fascinating because I find myself asking completely different questions.

The current Buster Bulb is a very warm 2500K and produces only around 60 lumens, so it is clearly designed to create atmosphere rather than flood an entire room with light. What I'd love to know now is how that same bulb performs in terms of flicker and temporal light modulation, particularly when dimmed.

I haven't been able to find published flicker data for the current bulb, so I wouldn't describe it as flicker-free without testing or seeing the manufacturer's measurements. But it is a great example of why I don't think this conversation should become simply incandescent good, LED bad.

LED gives designers extraordinary possibilities. The real questions are how we control it, how we diffuse or direct it, how warm or cool we make it, how much we use, and, increasingly for me, how stable that light actually is.

It's fascinating to revisit a product I discussed with its designer years ago and realise I am now asking completely different questions about it.

Light & Your Nervous System

Can your phone really reveal flicker?

This is something I have started experimenting with myself and mentioning to clients. If you open the camera on your phone and point it towards a light, particularly while recording video or slow motion, you may see dark bands moving across the image, pulsing or obvious flickering that you cannot consciously see when simply looking at the room.

The phone can reveal fluctuations in light output, but with an important qualification. It doesn't show us exactly what our eyes or nervous system see. A smartphone camera captures light differently from the human eye, and its shutter speed, frame rate, and rolling shutter can sometimes exaggerate, hide, or create patterns depending on how they interact with the light's frequency.

I therefore see the phone test as a useful first screening exercise rather than a scientific measurement. If I point my phone at an LED fitting and see pronounced rolling bands or pulsing, particularly when the fitting is dimmed, that would certainly make me want to investigate the product further. Equally, if the phone shows nothing, that doesn't necessarily prove that the light is completely flicker-free.

For me, it is simply another useful tool for becoming more aware of the quality of light we are putting into our homes.

Light is doing far more than helping us see

This is where the subject becomes particularly fascinating. Our eyes don't simply create the visual picture of the world around us. Specialised cells within the retina also communicate information about environmental light to systems involved in our circadian rhythm, alertness and sleep.

This is why the same amount of light can have very different implications on our nervous system depending on when we receive it. Bright light in the morning and during the daytime is something we actively want because it helps reinforce daytime alertness and our biological clock. Bright artificial light late in the evening, however, can send a very different signal at a time when the body should naturally be moving towards darkness and sleep.

It is also why I don't particularly like the simplistic message that “blue light is bad.” Blue-enriched natural daylight is an important part of daytime biology. The issue is more about timing, intensity, duration, and where that light is coming from.

In other words, we don't necessarily need one perfect type of light. We need lighting that changes as our needs and biology change throughout the day.

Lighting Design in your Home

What should our lighting look like throughout the day?

During the morning and daytime, I would always prioritise natural daylight wherever possible. Open the curtains and blinds properly, sit closer to windows when practical, and let the house feel bright. In darker areas where artificial lighting is required, somewhere around 3000K to 4000K may work well depending on the space and what we are doing in it.

As evening approaches, I want the environment to start changing. Lighting can become warmer—often around 2700K or below—but I also want considerably less of it. This is when I would naturally begin moving away from bright ceiling lighting towards lamps, wall lights and concealed sources.

Later in the evening, very warm lighting around 2200K to 2400K can create that lovely candle-like atmosphere, although Kelvin is only part of the story. Warm light shining brightly and directly into your eyes is still bright light. The amount of light, its position, and the time we are exposed to it matter just as much as its colour temperature.

The tiny lights I can't stop noticing

Once I started thinking about light in this way, I began noticing something else in my own home: tiny LEDs are absolutely everywhere.

I have them on my air scrubber and dehumidifier, and then there are lights on Wi-Fi equipment, alarm panels, toothbrush chargers, standby devices, bathroom controls, and even some modern shower toilets. During the day we barely register them, but at night we switch everything off, give our eyes several minutes to adjust to the darkness, and suddenly they become surprisingly obvious.

Where my equipment allows it, I now dim or completely switch off these displays at night. With other devices, I have occasionally covered the little indicator light, while obviously making sure I never obstruct ventilation, sensors, or anything there as an important safety warning.

It is actually quite an interesting healthy-home experiment to try yourself. Turn everything off in your bedroom tonight, wait five minutes for your eyes to adapt and then look around the room again. If you have an en suite, look through there as well. You might be surprised by how many little blue, green and white points of light remain.

It also makes me wonder why every piece of bedroom technology doesn't have a proper night mode that lets all non-essential illumination disappear completely.

LED Light Pollution

Then there is the light coming from outside

Even if we manage the light inside our homes, another source is largely out of our control. Streetlights, security lights, garden lighting, illuminated signs, neighbouring houses and passing cars can all introduce artificial light into a bedroom.

Blackout curtains and blinds are an obvious solution, but I think there is an interesting compromise here because I also love waking with natural morning light. If we completely seal ourselves into a dark room, we protect darkness while we sleep but can also lose that very useful morning light signal.

This is where thoughtful design and technology can work together. Automated curtains can stay closed overnight and open around waking time, shutters can block direct streetlight while still letting morning daylight into the room, and sometimes something as simple as repositioning the bed or planting outside can reduce a problem considerably.

The principle I keep coming back to is wonderfully straightforward: we want darkness while we sleep and natural light when we wake.

Do we really need all those spotlights?

This is something I increasingly question as a designer. Somewhere along the way, we became accustomed to seeing ceilings covered with rows of recessed spotlights, as though every square metre of floor needs exactly the same level of illumination.

It doesn't.

I think a much more interesting and comfortable room comes from layering light according to what we actually need. Ambient lighting provides comfortable background illumination; task lighting gives us brighter light exactly where we need to read, cook, work, or use a mirror; accent lighting highlights architecture, artwork, stone, and texture; and decorative lighting introduces beautiful pendants, wall lights, and lamps that become part of the interior itself.

I would also add low-level orientation lighting, particularly in bedrooms, bathrooms and circulation spaces. A tiny amount of warm, carefully concealed light close to floor level lets us move safely through the house at night without switching on a ceiling full of bright downlights.

For me, this is where good lighting design and healthy-home thinking come together beautifully. We aren't necessarily reducing a room's functionality; we are simply putting light where it is actually needed.

I would rather see the effect of the light

One of my strongest design preferences is increasingly to avoid seeing the brightest light source directly. I would much rather conceal light within an architectural pocket, wash it gently across a wall, illuminate joinery, bounce it from a ceiling or use a properly recessed fitting with good optical control.

In other words, I would rather see what the light is doing than stare at the light itself.

From a design perspective, this creates depth and atmosphere, but it can also reduce direct glare and create a much softer visual environment.

Why should a bathroom have the same lighting at 7 am and 10 pm?

Bathrooms are a perfect example of why I think we need to reconsider the way we light our homes. At seven in the morning, I may want excellent illumination around the mirror for makeup or getting ready. At ten at night, I may simply want to take a shower before bed.

Those two situations don't need the same lighting.

During the daytime, I want excellent functional task lighting. In the evening, perhaps all I need is a softly lit mirror, concealed niche lighting, or some very warm, low-level light. I certainly don't need six bright spotlights directly above my head when I am trying to wind down for sleep.

This is also where modern lighting technology becomes genuinely useful.

Lighting scenes can make the healthy choice automatic

We can now programme complete lighting scenes into our homes, which means we don't have to manually adjust six different switches and dimmers every evening.

A system might have Morning, Day, Cooking, Relax, Evening and Night scenes. Press Evening and the bright ceiling lights can switch off while wall lights, lamps and concealed lighting come down to a much softer level. Press Night and almost everything can disappear except for a tiny amount of warm orientation lighting between the bedroom and bathroom.

With tunable-white systems, the colour temperature can change, as can the brightness. More sophisticated whole-home systems can even integrate lighting with blinds and curtains so that the house responds to sunrise and sunset.

Smart systems range from relatively accessible options like Philips Hue to professionally designed systems such as Lutron HomeWorks and Ketra. For me, though, the technology itself isn't really the interesting part.

It is what we ask the technology to do.

I don't particularly want a smart home filled with gadgets simply because we can have them. I want a home where technology quietly makes the environment simpler, calmer and more intuitive for the people living there.

Try a light audit of your own home

The easiest way to begin is simply to walk around your home at different times of day and really look at the lighting. Notice whether you can see bright light sources directly, whether your LEDs show obvious flicker on your phone camera, and whether you genuinely need every spotlight switched on.

Then repeat the exercise at night. Look for all those tiny standby LEDs, notice whether artificial light enters through the windows, and consider whether you could comfortably move between your bedroom and bathroom without switching on a bright ceiling light.

Most importantly, notice how your home changes—or perhaps doesn't change—as evening arrives.

Once you start looking at lighting in this way, it becomes surprisingly difficult to stop noticing it.

So what is the perfect light?

I don't think any one bulb or magic Kelvin number is perfect.

The right light changes throughout the day. We want bright natural light in the morning, useful and well-positioned light during the day, warmer and softer light as evening approaches, minimal illumination at night, and, when we finally sleep, as much genuine darkness as our environment allows.

The healthy-home conversation has rightly focused on materials, indoor air quality, acoustics and temperature, but I increasingly believe that lighting deserves an equal place within it.

Not because every LED is somehow damaging our nervous system—the evidence doesn't support such a sweeping statement—but because light is one of the environmental signals our biology responds to every single day.

Perhaps, as designers, we need to stop asking “How much light can we put into this room?” and start asking “How much light does the person in this room actually need, where do they need it and at what time of day?” To me, that feels like a much more human way to design a home.

References & Further Reading

International Commission on Illumination (CIE)Research and technical guidance on circadian responses to light, melanopic light and temporal light modulation.

US Department of Energy – Solid-State Lighting Program. Research and technical guidance on LED flicker, temporal light modulation and methods of assessing flicker.

Brown, T.M. et al.Research into melanopic illuminance and human circadian responses, including melatonin suppression and circadian phase shifting.

UK Government – Planning Practice Guidance Guidance concerning artificial light and light pollution within the built environment.

Peer-reviewed research into combustion lighting: Studies examining indoor-air pollution and black-carbon emissions associated with kerosene and other flame-based lighting.

Buster + Punch – Buster Bulb Current product and technical information for Massimo Buster Minale's Buster Bulb, including its 2500K colour temperature, output and optical design.

Buster + Punch patent family Patent documentation relating to the Buster Bulb's light-pipe and optical arrangement.

Lutron HomeWorks & Ketra Technical information on programmable lighting scenes, tunable-white lighting and integrated shading.

Philips Hue: Technical information on programmable scenes, time-based lighting and Natural Light functionality.