Thermal comfort is not one thermostat number

One-sentence thesis

Comfort is produced by air temperature, radiant temperature, humidity, air movement, activity, clothing, bedding, expectation and control. A thermostat can measure only part of that system.

What this note covers

• the variables a thermostat cannot see;
• radiant heat and solar load;
• air movement and ceiling fans;
• humidity, dew point and latent load;
• personal control and adaptive comfort;
• why bedrooms require a separate night strategy;
• open, fan-first, closed, arrival and absence modes;
• what should be tested before release.

The thermostat sees air temperature, not the whole room

Established evidence Official standard and evidence-based recommendation

Current thermal-comfort standards treat comfort as a relationship between:

• air temperature;
• mean radiant temperature;
• humidity;
• air speed;
• activity;
• clothing;
• local discomfort;
• occupant expectations and adaptation.

In a residence, bedding, direct sun, hot surfaces, fan use, open doors, wet-season humidity and individual control make the system even more variable.

This is why DALLEAU does not define comfort through one thermostat number across every room, user and operating mode.

Radiant load comes before aggressive cooling

Established evidence Evidence-based recommendation

A person near a hot roof, warm wall or sunlit window can feel significantly warmer than the room thermostat suggests. The first question is therefore whether the room is hot because of the air or because of radiation from its surfaces.

Relevant design decisions include:

• external shading;
• roof insulation and ventilation;
• solar-control glazing where justified;
• west-facing exposure;
• reflected heat from hardscape and pool surrounds;
• furniture placement;
• tree and landscape shading;
• thermal mass and night-time release;
• whether the occupant sits or sleeps in a direct solar patch.

Reducing radiant load can improve comfort before additional cooling capacity is added.

Air movement is one of the strongest tropical tools

Established evidence Evidence-based recommendation

Ceiling fans and local air movement can expand the range of conditions people find acceptable in warm climates. They can also allow higher air-conditioning setpoints in suitable rooms and conditions.

The benefit depends on:

• humidity;
• fan diameter and speed;
• blade height;
• room geometry;
• furniture position;
• noise;
• where the air reaches the body;
• whether the occupant controls it.

“Fan-first” can be a strong operating principle. “Fan-only” is not a universal rule.

During high indoor dew point, heavy rain infiltration or a protected bedroom night condition, air movement may improve sensation without solving the moisture load. The fan and the latent-control strategy must therefore be coordinated.

Humidity changes both comfort and building risk

Established evidence Bali translation

Warm humid air limits evaporative heat loss and can make a room feel muggy even when the air temperature is not extreme. Deep cooling can lower the thermostat reading while introducing cold surfaces, draught and condensation risk.

The design needs to distinguish:

• sensible cooling, which lowers temperature;
• latent control, which removes moisture;
• air movement, which changes heat exchange and sensation;
• radiant control, which reduces heat received from surfaces and sun.

A thermostat alone cannot resolve that distinction.

Personal control is part of comfort

Established evidence Evidence-based recommendation

People differ. Age, acclimatisation, clothing, activity, health status, expectation and preference all change the response.

A residence should therefore provide simple, local and understandable choices rather than impose one central condition. Useful control may include:

• room zoning;
• ceiling-fan control;
• shading;
• operable openings where conditions allow;
• gentle bedroom airflow options;
• clear mode selection;
• manual override;
• staff defaults that do not erase owner preferences;
• power-recovery behaviour that returns to a safe, understandable state.

Control loses value when the interface is confusing or when occupants do not know what the system is doing.

Bedrooms are the exception that deserves its own brief

Established evidence Evidence-based recommendation

Night-time comfort differs from daytime comfort because:

• metabolic activity is lower;
• bedding changes insulation;
• air movement on the face or neck can become uncomfortable;
• AC noise and cycling become more salient;
• the room remains occupied for long, continuous periods;
• attached bathrooms add moisture;
• occupants are less willing to operate complex controls at night.

A protected bedroom brief should consider:

• radiant load at the bed;
• stable humidity;
• gentle, even air movement;
• AC discharge direction;
• fan sound and wobble;
• compressor and condensate noise;
• bedding assumptions;
• manual controls within reach;
• night and outage recovery modes.

Lowering the setpoint is not a substitute for coordinating those variables.

A Bali residence needs several comfort modes

Evidence-based recommendation DALLEAU project method

Open comfort mode

Used when outdoor heat, humidity, rain, particles, insects and noise permit useful opening.

Fan-first mode

Shade and air movement provide comfort before mechanical cooling is increased.

Closed comfort mode

Cooling, moisture control and outdoor air operate intentionally with doors and windows coordinated.

Night bedroom mode

Noise, humidity, airflow, radiant load and control simplicity take priority.

Arrival mode

The residence is prepared before occupancy without running every room at full output for unnecessary periods.

Absence mode

The building protects moisture-sensitive rooms, equipment and assets while avoiding a false assumption that an unoccupied tropical house needs no environmental control.

What DALLEAU would verify

DALLEAU project method Site-specific finding after testing

• late-afternoon solar-patch and surface-temperature review;
• occupied-zone air-movement map at beds, sofas and desks;
• AC discharge direction and local draught;
• fan sound, balance and speed steps;
• temperature, relative humidity and dew-point trends;
• open-to-closed switchover logic;
• night bedroom test;
• pre-arrival sequence;
• rainy-season vacancy behaviour;
• manual override and power recovery;
• staff understanding of mode selection.

What the evidence did not prove

The evidence does not establish that:

• one temperature is comfortable for everyone;
• a cooler setpoint guarantees better sleep;
• a fan always replaces dehumidification or AC;
• a thermostat reading describes radiant load, humidity or local draught;
• a short test predicts every season and user;
• adaptive comfort means every hot condition is acceptable;
• automation can infer the ideal personal condition without error.

Unresolved questions

• What comfort bands should be used for owners, guests and staff with different acclimatisation and expectations?
• How should Bali coastal, lowland and upland projects differ?
• Which fan and AC combinations remain quiet and even at actual bed positions?
• How should pre-arrival conditioning balance readiness, energy and moisture protection?
• What should the default mode be after a power interruption?
• Which measurements are useful enough for recurring POE without overwhelming the operating team?

Sources

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

1. Thermal Environmental Conditions for Human Occupancy

   Authoritative guidance. Thermal comfort as an interaction between temperature, radiation, humidity, air speed, activity and clothing. Limit: One thermostat setting that guarantees comfort for every person.

2. Ergonomics of the thermal environment — PMV, PPD and local thermal comfort criteria

   Authoritative guidance. Analytical evaluation of general and local thermal comfort in moderate environments. Limit: A universal residential setpoint or direct transfer without project context.

3. Occupant's preferred indoor air speed in hot-humid climate and its influence on thermal comfort

   Growing evidence. Controlled evidence that preferred air speed varies with thermal and humidity conditions. Limit: A universal air-speed target for every resident, room or activity.

Related content

• Theme: Thermal comfort in hot-humid residences
• Protocol: Protected Bedroom Performance Protocol
• Protocol: Indoor Environment and Moisture Control Protocol
• Methods Note: Why commissioning matters more than handover

Closing

Design the modes, not one universal number

DALLEAU Atelier carries thermal comfort through shading, envelope, MEP, local control, commissioning and operation.