Light by day, darkness by night

One-sentence thesis

The strongest residential lighting strategy is not one colour temperature or one automated scene. It is a sequence: enough light by day, a deliberate reduction in the final hours before bed, and darkness during sleep.

What this note covers

• daytime light and the eye-level exposure question;
• the evening reduction before sleep;
• darkness and light leakage during the sleep period;
• why warm colour temperature is not enough;
• how the question changes in a Bali residence;
• what should be checked in a mock-up and during commissioning;
• what the evidence does not establish.

The central finding

Established evidence Evidence-based recommendation

For day-active adults, the evidence converges on a simple pattern: brighter days, dimmer evenings and darker nights.

The detail matters. Human responses to light depend on timing, intensity, duration, spectrum, direction and prior light exposure. A fixture schedule that records watts, colour temperature and horizontal lux does not fully describe what reaches the eye.

A useful brief therefore starts with a 24-hour sequence rather than a list of decorative scenes.

Daylight is not only a window question

Established evidence Evidence-based recommendation

The first design question is whether occupants can receive useful morning and daytime light without unacceptable glare, heat gain or loss of privacy.

In a residence, that depends on more than glazing area. It depends on:

• orientation;
• exterior shading;
• room depth;
• view direction;
• where people actually sit, eat and work;
• whether the eyes face the bright part of the room;
• whether curtains remain closed because of glare, heat or privacy;
• whether the daily routine includes a terrace, garden or outdoor breakfast area.

Current consensus recommendations for healthy adults on regular daytime schedules use about 250 lux melanopic equivalent daylight illuminance at the eye during the day as a minimum reference point. This is not a universal threshold and it is not a guarantee of a sleep or health outcome. It is a useful briefing and measurement reference when the room, user and specialist review justify it.

Residential implication

A bright floor does not prove useful eye-level exposure. A large west-facing window may provide plenty of light while creating heat and glare that cause the blinds to remain closed. A shaded breakfast terrace may be more useful than a brighter-looking interior photograph.

The relevant question is not simply, “Does the room have daylight?” It is, “What light reaches the occupant’s eyes, at what time, in the places where the daily routine actually happens?”

Evening light needs a deliberate taper

Established evidence Evidence-based recommendation

The final hours before sleep should not reproduce the intensity and direct visual brightness of the daytime environment.

Consensus recommendations use about 10 lux melanopic equivalent daylight illuminance at the eye as a maximum reference during the three hours before bed for healthy adults on regular schedules. Again, this is a design reference, not a person-level promise.

The practical issue is often not one ceiling light. It is the accumulation of:

• bright downlights;
• illuminated mirrors;
• decorative pendants in direct view;
• television and device screens;
• bright dressing-room light;
• bathroom spill;
• terrace and garden lighting;
• control-panel indicators;
• staff reset scenes that return every circuit to full output.

A useful evening scene reduces the total visual load. It limits direct-view brightness, keeps task light local, preserves safe movement and returns automatically to a quieter state after temporary use.

Darkness is a measurable design condition

Established evidence Evidence-based recommendation

“Lights off” is not the same as darkness.

The sleep-period reference in current consensus is about 1 lux melanopic equivalent daylight illuminance or less at the eye, with only temporary local exceptions for unavoidable visual tasks.

In a real bedroom, darkness should be checked from the pillow position with the residence in its actual night mode. That means:

• blackout closed as staff or occupants will actually close it;
• bathroom and dressing-room doors in realistic positions;
• corridor and landscape lighting active;
• all equipment and charger indicators present;
• air conditioning and control panels running;
• exterior neighbours and road sources considered where visible.

A small source in direct view may be more disturbing than a larger source hidden below the sightline. The check therefore needs both a measurement and a visual inspection.

What to inspect

• top, side and bottom blackout leakage;
• curtain overlap and track geometry;
• light around door frames;
• bathroom mirror and vanity spill;
• terrace and pool reflections;
• garden uplights visible from bed;
• smoke detector, router, television and charger indicators;
• low-level navigation light and its automatic timeout;
• power-recovery behaviour after an outage.

Warm light is not automatically quiet light

Established evidence Research translation

Colour temperature describes visual appearance. It does not fully describe the spectrum, melanopic content, eye-level intensity, duration or direct-view brightness of a source.

Two light sources can both be labelled 2700 K and still produce materially different conditions at the eye. A very bright warm source can remain inappropriate late at night. A lower-output source with better direction and control may create a much quieter condition.

This is why DALLEAU does not treat “warm light” or “tunable white” as a complete circadian strategy. The brief still has to resolve:

• timing;
• eye-level exposure;
• spectrum where relevant;
• dimming depth;
• direct view;
• scene duration;
• blackout;
• exterior spill;
• manual override;
• staff operation.

The Bali translation

Established evidence Site-specific validation required

Bali changes the execution, not the underlying sequence.

Morning light is relatively available throughout the year, but the residence may still block it through deep roofs, dense planting, privacy screens or closed curtains. Evening and night conditions can be harder because indoor and outdoor space are closely connected.

Relevant local variables include:

• early sunrise and outdoor routines;
• heat gain that encourages occupants to close shading;
• open-air circulation beside protected bedrooms;
• terrace, pool and landscape lighting;
• neighbouring villas and road light;
• staff turnover and inconsistent room reset;
• power interruption and scene recovery;
• bathroom humidity that keeps doors open after use;
• insect-control lighting and exterior security requirements.

The project answer is usually a coordinated set of modes, not one permanent setting:

1. wake and morning;
2. daytime;
3. late afternoon;
4. evening;
5. sleep;
6. night-time movement;
7. staff reset;
8. outage recovery.

What DALLEAU would verify

DALLEAU project method Site-specific finding after testing

1. Define the intended day, evening, night and wake modes.
2. Review orientation, shading and exterior-light relationships.
3. Confirm fixture, driver, dimming and control assumptions.
4. Build or stage the critical bedroom condition at useful scale.
5. Test minimum levels, direct view, glare and leakage at night.
6. Verify blackout edges, bathroom spill and exterior spill.
7. Test manual override, outage recovery and staff reset.
8. Record the accepted result, deviations and unresolved seasonal questions.

The evidence record may include:

• annotated light sequence;
• eye-plane and pillow-zone measurements where required;
• blackout and leakage checklist;
• fixture and driver confirmations;
• scene and dimming test records;
• mock-up photographs;
• commissioning exceptions;
• Building Passport entries;
• 30-day or seasonal observations when included.

What the evidence did not prove

The evidence does not establish that:

• one lighting scene works for every person;
• warm light is automatically appropriate in the evening;
• tunable white automatically creates circadian lighting;
• a residence treats insomnia or jet lag;
• a measured light condition proves a sleep, mood or cognitive outcome;
• one short commissioning test predicts every future season, user or operating routine.

A project can document the environment it created and the way it was tested. It cannot infer a medical result from those conditions alone.

Unresolved questions

• How should reference values be adjusted for children, older adults, extreme chronotypes and people arriving after long-haul travel?
• How much does a typical open-air Bali daily routine change evening sensitivity compared with a dim indoor day?
• Which blackout details remain robust after repeated staff operation, cleaning and material movement?
• How should exterior security and insect-control lighting be balanced with protected bedroom darkness?
• Which low-cost field instruments are sufficiently reliable for recurring project use after specialist comparison?

Sources

The source finding and DALLEAU's residential interpretation are kept separate. Links open the original publisher or authority record.

1. CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light

   Established evidence. The measurement quantities and metrics used to describe stimulation of the five retinal photoreceptor types. Limit: A complete lighting application, a health treatment or prediction of a person-level outcome.

2. What to document and report in studies of ipRGC-influenced responses to light

   Authoritative guidance. A reporting template for stimulus conditions and use of the CIE S 026 measurement system. Limit: An efficacy claim or a universal residential target.

3. Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults

   Established evidence. Consensus reference values for healthy adults aged 18–55 on regular daytime schedules. Limit: A universal prescription for every age, health condition, routine or residence.

4. Melanopic illuminance defines the magnitude of human circadian light responses under a wide range of conditions

   Growing evidence. Melanopic illuminance as a strong predictor across pooled laboratory datasets of circadian light responses. Limit: A complete residential outcome or a claim that one light metric replaces the full design brief.

5. CIE Position Statement on Integrative Lighting — Recommending Proper Light at the Proper Time, 3rd Edition

   Authoritative guidance. Use of CIE S 026 metrics and a daily pattern of more light by day, less before bed and near-darkness during sleep. Limit: A treatment promise or an unqualified target for every population.

6. Melanopic irradiance defines the impact of evening display light on sleep latency, melatonin and alertness

   Emerging research. A controlled display-light experiment in 72 healthy males aged 18–35 under specific pre-bed conditions. Limit: A long-term residential outcome, a general population effect or a universal design threshold.

Related content

• Theme: Light and sleep
• Protocol: Protected Bedroom Performance Protocol
• Methods Note: How DALLEAU reads evidence for private residences in Bali
• Methods Note: Why commissioning matters more than handover

Closing

Bring the full day and night sequence into the brief

DALLEAU Atelier carries the light question through the owner brief, specialist scope, mock-up, controls, commissioning and operating record.