Category: daylight

Quick summary: Light affects neurodivergent children more than most people realise — fluorescent flicker and glare can cause genuine sensory distress for autistic pupils, while many children with ADHD have a naturally delayed body clock that morning light helps reset. September brings both a classroom-design opportunity and a home-routine opportunity to use light more deliberately, right as the clocks are also starting to work against you as autumn draws in.

I get to see this from two sides. As a physics teacher, I’m in a classroom every day. As a daylight and building physics consultant, I spend my working life thinking about how light in a space actually affects the people in it. September — the return to school, and the moment natural daylight starts quietly shrinking day by day — is where those two things collide most usefully.

Why light matters more for neurodivergent children

This isn’t a fringe idea. Autism-friendly design guidelines consistently name two specific issues: reducing glare and avoiding fluorescent lighting because of its flicker. Around half of autistic people report severe sensitivity to fluorescent lighting, and early experimental studies found an observed increase in repetitive behaviours in autistic children specifically under fluorescent light, compared with other lighting types. The mechanism isn’t a behavioural choice — sensory processing research in autism consistently finds atypical responses in the pathways handling visual input, meaning the discomfort has a real physiological basis, not just a preference.

For children with ADHD, the light issue is different but just as real: a growing body of research links ADHD to a delayed circadian rhythm — many children with ADHD show a melatonin release roughly 45 minutes later than their neurotypical peers, making early starts feel genuinely harder, not just less-willed. Morning light exposure is one of the most consistently effective ways to help shift that internal clock earlier, alongside consistent wake times and reduced evening light.

Put simply: the way a classroom or a home is lit isn’t neutral. For a meaningful number of children, it’s either actively working against their regulation and focus, or quietly supporting it.

At school: what actually helps

Favour daylight over fluorescent wherever possible. Daylight doesn’t flicker the way older fluorescent fittings do, and glare reduction and flicker avoidance are already standard recommendations in autism-friendly design guidance. Where fluorescent fittings can’t be replaced immediately, checking and replacing failing tubes promptly matters — a flickering fitting is a much bigger problem than a working one.

Reduce glare, not just brightness. Glare off whiteboards, shiny desks or laminated surfaces can be as disruptive as the light source itself. Positioning screens and seating away from direct glare, and using external shading rather than closing blinds fully, keeps daylight usable without the discomfort.

Give the room a lower-stimulation option, not just a single fixed setting. A classroom that can dim, or that has a quieter corner with softer, warmer light, gives a child somewhere to regulate without leaving the room entirely. This is a genuine echo of what “adaptable” has come to mean in inclusive school design more broadly — flexibility and adaptability is now an explicitly named principle in national guidance on designing for SEND pupils, alongside sensory awareness.

Run a simple sensory lighting audit. Sensory audits already used in SEND settings ask straightforward, practical questions: are fluorescent lights regularly checked for flicker? Is light through blinds creating distracting patterns? Is light reflecting harshly off metal or shiny surfaces? None of these require a specialist visit to answer — a walk through the room with those three questions in mind is often enough to find the quickest wins.

Warmer colour temperature helps more than people expect. Research on light sensitivity in autism suggests cool, blue-toned light is more likely to feel overwhelming than warmer tones, closer to natural light at dawn or dusk. Where electric lighting is unavoidable, warmer settings are generally better tolerated than the cool white light common in older school fit-outs.

At home: the transition, and the season working against you

September brings two things at once for families: the return to a fixed routine after weeks of holiday flexibility, and the start of shrinking daylight hours heading into autumn. For a lot of neurodivergent children, both make mornings harder — right at the point they need to get easier.

Morning light is doing real work, not just “waking someone up.” Circadian research shows a week of natural light-dark cycle exposure can shift the body’s internal clock earlier by over two hours in adults, and similar light-based approaches are increasingly being studied specifically as a support for ADHD’s circadian component. Opening curtains fully at wake-up, having breakfast near a window, or a short walk to school rather than a car journey all give a child’s body clock a genuine morning cue — not just a mood boost.

The clock is working against this exact strategy as the term goes on. As autumn deepens, morning light gets weaker and arrives later — the same helpful morning light exposure becomes harder to get by October and November, right as the novelty of “back to school” routine has also worn off. Building the habit early in September, while there’s still strong morning light to work with, makes it easier to sustain once the mornings genuinely darken.

Evenings matter as much as mornings. Reducing bright, cool-toned light in the hour or two before bed — dimming main lights, favouring warmer lamps, easing off screens — supports the same circadian system morning light is trying to reset in the opposite direction. Think of it as a matching pair of cues, not two separate problems.

Keep it environmental, not clinical. These are genuinely useful, low-cost design changes — not a treatment, and not a substitute for support from a SENCO, GP, or paediatric sleep specialist where a child has a diagnosed sleep or sensory difficulty. Light is one lever among several, and every child’s sensory profile is different.

Frequently asked questions

Why are some autistic children so bothered by classroom lighting? Many autistic people have heightened sensory processing responses to visual input, and fluorescent lighting in particular can produce a flicker that, even when not consciously visible, causes measurable discomfort. Roughly half of autistic people report severe sensitivity to fluorescent lighting specifically.

Does morning light actually help children with ADHD get up more easily? There’s a real, growing evidence base linking ADHD to a delayed circadian rhythm, and morning bright light exposure is one of the most studied non-medication approaches to shifting that rhythm earlier. It isn’t a guaranteed fix for every child, but it’s a low-risk, well-evidenced starting point.

What’s the single easiest change a school could make this September? Running a short, informal sensory lighting walk-through of a classroom — checking for flickering fittings, glare off shiny surfaces, and harsh patterns of light through blinds — usually surfaces at least one quick, low-cost fix without needing a specialist assessment first.

Is warm or cool lighting better for neurodivergent pupils? Research on light sensitivity in autism suggests warmer colour temperatures are generally better tolerated than cool, blue-toned light, which is more likely to trigger sensory overload. This varies by individual, so it’s worth treating as a starting point rather than a fixed rule.

Key takeaways

Light isn’t a background detail for a meaningful number of neurodivergent children — it’s an active factor in comfort, regulation and routine. September gives schools and families a natural moment to reset both: a classroom lighting audit costs nothing and often finds a quick win, and a consistent morning-light habit at home is easiest to build right now, before the year’s daylight starts working against you. Small, environmental changes — not clinical interventions — are often the most realistic place to start.

Sources

• Beaver, C. (2010); Hewitt, L. et al. (2009); Humphreys, S. (2005) — cited in classroom design research on autism-friendly guidelines regarding glare and fluorescent lighting.
• Colman, R.S. et al. (1976); Fenton, M. & Penney, R. (1985) — early studies on fluorescent lighting and repetitive behaviours in autistic children.
• TheraSpecs and Super Bright LEDs, clinical-adjacent summaries on light sensitivity prevalence and colour temperature preference in autism.
• Jones, V. & Attfield, I., Sensory Audit for Schools and Classrooms.
• Frontiers in Psychiatry (2025), “ADHD as a circadian rhythm disorder: evidence and implications for chronotherapy.”
• Misiunaite, I., Eastman, C.I. & Crowley, S.J. (2020), “Circadian Phase Advances in Response to Weekend Morning Light in Adolescents,” Frontiers in Neuroscience.

Daylight is one of the best things a classroom can have — better than the alternative, and something pupils and teachers consistently prefer. But daylight without control brings its own problem: glare. Get it wrong, and the very windows meant to make a classroom feel good end up forcing the blinds shut and the lights on for the rest of the day.

Classrooms deserve their own conversation on this, separate from the office glare research most guidance is built on — because a classroom behaves quite differently.

Why classrooms are a trickier glare environment than offices

Most daylight glare metrics and guidance were developed with office environments in mind: one desk, one occupant, some control over blinds and seating position. Classrooms break most of those assumptions.

• Room proportions and layout. Classrooms are typically deeper than they are wide, lit from a single window wall, with rows of desks running perpendicular to it. A pupil at the front, by the window, and a pupil at the back of the room can be experiencing completely different lighting conditions during the same lesson.
• Screens sit low in the field of view. Interactive whiteboards and laptop screens compete directly with window brightness, and unlike a printed page, screen content disappears entirely under strong glare rather than just becoming harder to read.
• No individual control. Office workers can usually reposition themselves or adjust their own blind. In a classroom, one set of blinds and one layout has to work for 25–30 pupils with different sightlines, and the teacher — not the affected pupil — is the one managing it.
• All-or-nothing blind behaviour. Manual blinds are slow and fiddly to fine-tune mid-lesson, so in practice they tend to get shut completely rather than adjusted to the specific problem — killing daylight and views for the whole room to fix a problem affecting only some of it.

Common issues in practice

• Whiteboard and screen washout — direct sun or bright sky on an interactive whiteboard can make it unreadable.
• Veiling reflections — glossy desks, laminated worksheets, or screens reflecting a bright window back into a pupil’s eyes.
• Low-angle sun — east- and west-facing classrooms catching direct sun near eye height in the morning or afternoon, often worse than a south-facing room dealing with high summer sun.
• Contrast glare — even without direct sunlight, a bright window against a dim classroom interior can be genuinely uncomfortable, because of the sheer luminance difference the eye has to cope with.

How glare is formally evaluated

Daylight Glare Probability (DGP) is the standard simulation-based metric used to assess daylight glare, and it’s generally considered the most reliable of the available indices because it was developed and validated against real occupant responses, rather than derived purely theoretically. It’s assessed at seated eye height, usually at the position expected to be worst-case — typically a desk close to the window, with the sun potentially in the occupant’s field of view.

Under BS EN 17037, the European daylight standard, glare is assessed across a full year of occupied hours (8am–6pm, Monday to Friday), and a maximum of 5% of those hours are allowed to exceed a chosen DGP threshold — commonly 0.35, roughly the boundary between “perceptible” and “disturbing” glare — at the evaluated position.

Worth knowing specifically for schools: dedicated classroom research has found that standard glare metrics predict discomfort poorly for pupils seated away from the window — the usual single worst-case-desk assessment can miss real glare complaints happening elsewhere in the room. Researchers have proposed classroom-specific, seating-position-adjusted versions of DGP to address this gap. It’s a good question to ask of any classroom glare assessment: has it only checked the desk nearest the window, or has it considered the room as a whole?

Mitigation: what actually works, roughly in order

1. External shading — brise-soleil, overhangs, or planting such as deciduous trees and climbers trained over windows. Intercepting sun before it reaches the glass controls both heat gain and glare together, and is generally more effective than anything applied inside the room.
2. Solar control or fritted glazing — reduces transmitted brightness while preserving some view out, useful where external shading isn’t feasible.
3. Internal blinds with diffusing or low-transmittance fabric — a cheaper retrofit option, though less effective at controlling heat than external shading, and only as good as how consistently they’re actually used.
4. Desk and screen orientation — angling whiteboards and seating rows away from direct window sightlines, where the room layout allows it.
5. Light shelves or splayed window reveals — bounce daylight higher into the room while reducing direct low-angle glare at eye level, particularly useful on east- and west-facing classrooms.
6. Easy-to-adjust or automated blind controls — directly addresses the all-or-nothing problem. A system a teacher can quickly nudge partway through a lesson is far more likely to get used well than a manual pull-cord blind that’s easier to leave fully shut.

To summarise…

Glare in classrooms isn’t just a smaller version of the office problem — the room geometry, the screens, and the lack of individual control all make it genuinely different, and worth assessing as its own thing rather than borrowing office-based rules of thumb. Good early-stage design — orientation, shading, glazing choice — does far more work here than any amount of blind-adjusting after the building’s finished.

It’s a perk to get on well with your boss and stay in touch after you’ve parted ways. It’s a boon when that former boss puts on fabulous gigs in beautiful venues as a hobby — and is still inviting you to them decades later.

On Friday I went to Wild Hare Club’s 21st birthday, and as ever, the music and conversations were unforgettable. Walking into one of Richard Page’s gigs feels like stepping into another world.

Once upon a time, Richard was my boss on Greenpeace International’s Oceans team, back when I was a rookie campaigner.. That job took me to some unusual places: time aboard the Arctic Sunrise and Vega, press work in the run-up to the International Whaling Commission meeting, and eventually attending the meeting itself, wide-eyed and taking it all in. Richard steered me through that world with wisdom, good humour, and an apparently bottomless list of music recommendations. None of it would have been possible without Judy Wong Ming and the Black Environment Network, who opened doors for me that are, remarkably, still bearing fruit decades later.

Richard’s Wild Hare Club has been running for 21 years now, and Friday’s anniversary gig in Hereford was a proper showcase of what makes it special: three bands, each one hand-picked from Richard’s extensive and eclectic treasure trove: an intergenerational ska-jazz fusion collective opened proceedings; an alt-country circus band; a Senegalese master drummer.

Meanwhile, I had the pleasure of asking a top scientific advisor loads of questions. When the audience is that interesting, the bands can only be larger than life

Many Happy Returns Wild Hare.

Baggy tousers, dirty shirt, pulling hair and eating dirt. So much learning happens through play. Einstein branded it the highest form of experimentation. But in recent decades, time devoted to unstructured play has declined. As has eating dirt, which we now know can be good (in small amounts) for a kid’s microbiome. PlayDay is just one of the many initiatives aimed at reversing that trend. And it stands for something (see the graphic).

So, how can the built environment grown-ups lend a hand? Here is my two-penneth, from a building physics point of view.

Sun

• Map sun and shade over the day and seasons for your site, then zone the playground accordingly (e.g. “winter sun / summer shade” areas, “cool refuges”, “active sun zones”)
• Shade using groups of deciduous trees. Groups of planting are better for tree health, kids prefer them, they aren’t counted on your BRE shady amenity place check but do provide shade.
• If you really want to cool the area, you’re looking at 30-50% canopy cover. Go-on, I dare you.
• Stay away from high thermal mass ground cover and dark colours and mental things. Touch temperatures Prioritise high‑albedo, low‑thermal‑mass surfacing (light rubber crumb, pale resin‑bound gravel). Dark EPDM, metal slides and handrails can exceed safe touch temperatures in direct sun, creating burn risks. As if that wasn’t enough, hard surfaces amplify noise, which affects comfort and supervision. Soft landscaping can be added to reduce reverberation.
• Use low emisitivy, light cloured (but not shiny) materials, e,g, timber, especially in sundrenched areas.
• Avoiding glare from metal slides and bright plastics which can cause specular reflections; use matte finishes and avoid slides pointing south.

Wind

• For playgrounds near roads, maintain ≥10–15 m separation or use vegetation barriers with porous canopies to enhance pollution dispersion.
• Ensure that planting and fencing still allows 0.5–2 m/s air movement. Fully enclosed courtyards can trap warm air and raise MRT.
• Break up solid barriers and choose planting of appropriate heights e.g. crown height minimum 3m for trees, to avoid stagnant zones. Recessed corners, high fencing, and dense shrubs can create low‑wind pockets that increase heat stress.
• Use evergreens in the predominant winter wind direction to reduce winter windchill.

Rain

• Permeable surfacing — SuDS‑compatible surfaces reduce puddling and evaporative humidity. Wet rubber surfaces increase slip risk and prolong cooling times.
• Drying time modelling — Timber play structures retain moisture; orient them for morning sun to accelerate drying and reduce mould growth.

Other Guidance

We’ve put together a list of a few of our favourite online sources on this topic

From Canada a wonderful comprehensive design guide

Also from Canada, a reort on thermal comfort in playgrounds, bearing in mind the extremes of that climate

Some London outdoor thermal comfort design advice

The Town and Country Planning Association Children and Young People has more guidance on play provision in the built environment

Find more on Playday here

Natural light. The source of energy that’s essential for so many processes in our bodies. An influencer on our mood and free source of light and heat. If we’re not careful, however, it’s an extreme source of discomfort from overheting or glare. So, in the built environment, what does good daylight/sunlight design mean? Designing with the sun means getting the geometry right to harness useful solar energy and block unwanted solar gains for interior and exterior spaces around buildings, throughout the year.

INTERIOR: Let’s start inside. Good natural lighting is high on the list of what people look for in a home. So, here are the ingredients for getting it right.

Orientation. Keep the main axis running East-West-ish, so the building is facing within 30 degrees of south. Main living areas should be on this facade.

Window position: keep them high in the wall to throw light as far into the room as possible. Horizontal windows disperse light around a room and function better than vertical ones, all things considered (e.g. ventilation, view, desirable solar gain…). The height of the window influences the distance into the room at which good daylight can be achieved.

Floor plans should be limited by the rule of thumb for room depth: good daylight will be achieved at a distance into the room of 2 times the window head height for an unobstructed window e.g. if the window head is 2.5m, the daylight will be sufficient up to 5m into the room.

Window size: affects heat loss and useful solar gain, view and ventilation and really depends on the individual building and its surroundings. 25% of the facade is a reasonable stating point.

Glazing type: We ask a lot of the glass in our windows. We want it to keep heat in sometimes and block it’s arrival at others; it needs to let us see out and illuminate the room. The glazing’s g-value tells us how much solar heat it lets through. It’s different from it’s visible light transmission (VLT) which tells us how much light reaches inside. Low g-values are promoted to guard against overheating. However, we need glass to allow in useful heat gains in winter and there is now extensive research showing the importance to human health of some of the wavelemgths this glass may cut out. Broadly speaking, the more pains of glass, the better for heat loss but the more good wavelengths are cut out. The industry is just waking up to this so for now, choose a glass with g=0.5 or 0.6 and visible light transmission of 0.7; consider varying it around building and using internal thermal shutters to make up for heat loss – like on a plane

EXTERIOR: use of water features and planting (such as green roofs, green walls, trees and shrubs) can lower local indoor and outdoor temperatures and ease the urban heat island effect. These strategies work best alongside building‑level measures that limit solar gain.

Solar Absorption or Albedo: extensive dark, hard surfaces should be avoided because their low albedo means they absorb more solar radiation and raise surrounding air temperatures. Re-radiation of heat from hard surfaces can be the main source of overheating in urban spaces.

Spacing: if developing a group of buildings, use the rule of thumb for: ows a distance of 1,5 times the building height reduce heights to the south to preserve solar access further north where the tallest buildings should be.

Shading: South-facing windows not shaded by their surroundings will need horizontal shading to cut out high-angle summer sun but let in much-appreciated winter sun. Rule of thumb for overhang length: half the height of the window. East and West facing glazing needs vertical shading to block highly penetrating, direct low angle summer sun, Where shading is needed, use external, moveable shading (see here)

Courtyards: lower heights in the south is important for courtyards which also need gaps to ensure some winter sun gets through and the interior isn’t in shade all year round. Use deciduous tree to the north of courtyard spaces to create deliberate summer shade and coolth.

Balconies should be the sticky-outy type and staggered up the facade, not one above another.

Playgrounds: make sure that sun will fall on them during colder weather. Deliberately create shady areas (several small ones is better than one big one), Ideally, consider tree planting which will create dense shade as it matures. Do not, repeat DO NOT use hard surfacing. Ideally, the hole area willprovide access to dirt on the floor but particularly ensure that the ground spaces receiving sun in the summer are shaded in summer. The recommended guidance is for at least 50% of the playground to receive direct sun on the equinox (not counting trees) but more is better. Double check the solar access for 9-3 on a winter weekend when it’s likely to be used.

Gardens: again, at least half the space should receive sun on the equinox but gardeners will thank you for more. Plant for shade and water retention

Planting: trees can be used to offer additional shading for buildings and public spaces. Deciduous species provide summer shade but allow winter solar gains once the leaves have fallen. Select species for drought resistance canopy cover, canopy density and crown height over 3m. Groups of trees are better than one. If you’re aiming to reduce the temperature of an area (e.g. playground or neighbourhood block) significantly, the canopy coverage needs to be 30-50%. Site planting outside north-facing windows to provide good infra-red bathing. Site deciduous trees to the south and south-west to shade from powerful summer sun.

The blackberries have peaked so a new school year must be round the corner.

Bursars trying to balance their books will continue to be challenged by high energy prices, so this week I’m dusting off the results from pilot studies we ran with five London primary schools a few years ago, in case they come in handy. A three-point summary: (1) it is possible to make substantial savings on school energy bills at little or no expense; (2) involving the whole school was recommended by site staff, was linked to increased savings and has a host of educational benefits for teachers and pupils eager for experiential learning; (3) the construction industry and academia could (and should) benefit from the data produced by students from KS2 onwards.

The project was nice: keen university students, fresh from their course, were paired with an experienced engineer or architect, to study a primary school, and quantify ways to make carbon and financial savings from energy efficiency measures and renewables. They also looked a little at wider issues like comfort. Some schools signed up for assemblies, educational workshops and meetings with site staff and teachers which appeared to make a difference to their subsequent energy savings. It made a huge difference to the ease of data collection for the students.

Each school received a useful report full of ideas and engagement activities, all free. UCL students were paid (via a GLA grant) and gained valuable experience. The construction industry consultants gave their time pro-bono (thanks again to all involved) and received insights which can be hard to find e.g. the graph to the right…

It’s a while since I taught in a primary school. I imagine that teachers are even more pushed for time these days. The project aimed to make recommendations which wouldn’t add to teachers’ workload. With that in mind, the simplest recommendation assigned two keen students as monitors to reset the classroom after each lesson so that the need for blinds-down, lights-on was assessed each day.

I’d love to hear from anyone who has tried this. Happy to share more insights. Do get in touch.