Indoor environment and moisture control in Bali residences

One-sentence thesis

A cool room can still be moisture-loaded, under-ventilated or poorly controlled. The right sequence is source control, local extraction, intentional outdoor air, filtration for a defined question, then monitoring and action.

What this note covers

• source control and local extraction;
• ventilation and the limits of split AC;
• humidity, dew point and room-specific moisture risk;
• filtration and what it cannot do;
• what CO2 can and cannot indicate;
• open, mixed, closed and absence modes;
• monitoring, maintenance and staff response;
• what the evidence does not establish.

Start with the source

Established evidence Evidence-based recommendation

The most effective sequence is usually:

1. reduce or isolate the source;
2. extract where the source occurs;
3. manage outdoor air and moisture;
4. filter for a defined pollutant question;
5. monitor trends and act.

This order matters because a sensor can reveal a problem without resolving it. A purifier can reduce particles while leaving humidity, carbon dioxide, cooking gases or hidden wet materials unchanged. Cooling can lower air temperature while the room remains moisture-loaded.

Typical sources in a Bali residence

• rain and envelope leakage;
• wet construction and incomplete dry-out;
• showering and bathing;
• indoor drying and laundry;
• cooking and combustion;
• fragranced cleaning and scenting;
• outdoor particles, smoke and dust;
• condensate faults;
• damp storage and packed wardrobes;
• drains and traps during long absence;
• unplanned opening during high outdoor dew point.

Split air conditioning is not an outdoor-air strategy

Established evidence Evidence-based recommendation

A typical split AC unit recirculates room air. It may cool and remove some moisture, but it does not by itself provide an intentional supply of outdoor air.

Closed bedrooms, studies, media rooms and staff rooms therefore need a separate answer to the ventilation question. The answer may use natural ventilation when outdoor conditions are favourable, mechanical outdoor air when they are not, or a mixed approach.

The decision should consider:

• occupancy;
• outdoor humidity and dew point;
• outdoor particles and smoke;
• rain;
• noise;
• insects;
• privacy and security;
• energy and maintenance;
• whether the operator can understand and service the system.

Moisture needs room-specific targets

Established evidence DALLEAU project target

There is no credible single humidity number for every room, every season and every operating mode.

For enclosed, mechanically cooled and occupied rooms in Bali, DALLEAU defines project-specific humidity and dew-point operating bands with the appointed building-services and indoor-environment specialists. Persistent departure from those agreed bands should trigger investigation; this page does not present one universal percentage or dew-point threshold for every residence.

These are not universal health thresholds. They are operational warning references used to identify sustained moisture risk, not to condemn every short monsoon excursion.

Why duration matters

A short rise after a shower is different from a wardrobe that remains humid for days. A temporary open-mode condition is different from a closed room that never dries. The response therefore depends on:

• duration;
• room use;
• surface temperature;
• airflow;
• construction moisture;
• proximity to exterior walls or ground;
• material sensitivity;
• maintenance history.

The high-risk rooms are not always the obvious rooms

Established evidence Bali translation

Bedrooms

Risk from closed doors, recirculated cooling, occupancy, attached wet rooms, low air movement and long night-time exposure.

Walk-in wardrobes and owner storage

Risk from packed storage, perimeter walls, leather, linen, low circulation and long vacancy.

Bathrooms

Risk from steam, slow dry-down, weak extraction, open doors, hidden leakage and traps during absence.

Kitchens

Risk from particles, combustion gases, grease, moisture, staff workflows and extraction without a practical makeup-air path.

Laundry and utility rooms

Risk from wet textiles, internal drying, closed doors, condensate, equipment heat and insufficient extraction.

Staff spaces

Risk from higher occupancy density, simpler systems and under-ventilation that may receive less design attention than owner areas.

Plant rooms, garages and generators

Risk from combustion, water, heat, equipment leakage and pathways that connect technical areas to occupied rooms.

What CO2 can show

Established evidence Instrument limitation

When people are the dominant source and the air is reasonably well mixed, carbon dioxide can support a ventilation question. It can help show whether a closed, occupied room is receiving enough outdoor air for its actual use.

It cannot show whether:

• particles are low;
• volatile organic compounds are acceptable;
• mould is absent;
• carbon monoxide or nitrogen dioxide is absent;
• a purifier is working;
• hidden materials are dry;
• occupant symptoms are caused by the room.

A low CO2 reading in a cool room does not prove that the room is moisture-safe. A particle filter can reduce PM2.5 while carbon dioxide continues to rise. A gas-cooking event can complicate the interpretation.

The practical rule is simple: use CO2 as one narrow signal, not as a verdict on air quality.

Filtration answers only the question it was designed to answer

Established evidence Evidence-based recommendation

Sealed and correctly sized fine-particle filtration can reduce indoor particle levels. Its performance depends on:

• airflow;
• filter class and pressure drop;
• installation leakage;
• room size;
• source strength;
• operating time;
• outdoor conditions;
• replacement and maintenance.

Filtration does not remove moisture. It does not replace kitchen extraction. It does not correct a wet wall. It does not prove that air is “healthy”.

Devices that intentionally generate ozone should not be used in occupied residential spaces.

A Bali residence needs operating modes

Evidence-based recommendation DALLEAU project method

Open mode

Used when outdoor humidity, particles, rain, noise, insects and security allow beneficial opening.

Mixed mode

Selected openings and fans operate while protected rooms or high-risk zones remain controlled.

Closed mode

Outdoor air, filtration, dehumidification and cooling are intentional. Windows and doors do not undermine the system.

Absence mode

The residence protects enclosed rooms, wardrobes, drains, leaks, critical assets and data while the owner is away.

Extreme-weather or disruption mode

The residence responds to heavy rain, smoke, power interruption, equipment fault or network loss with understandable fallback actions.

A mode is only useful if the staff can recognise it, activate it and know what to do when conditions drift.

What DALLEAU would verify

DALLEAU project method Site-specific finding after testing

• room-by-room source and moisture risk map;
• outdoor-air strategy for protected rooms;
• kitchen, bathroom and laundry extraction;
• makeup-air paths;
• condensate routes and cleanability;
• filter access, seals and replacement path;
• wardrobe and storage circulation;
• leak detection and escalation;
• absence-mode sequence;
• sensor type, location, interval and limitations;
• staff response to sustained drift;
• wet-season and drier-season questions.

Evidence may include airflow checks, dry-down trends, temperature and relative-humidity records, dew-point review, particle trends, CO2 trends where relevant, leakage inspection, filter records, condensate inspection, staff training and corrective-action logs.

What the evidence did not prove

The evidence does not establish that:

• a sensor proves healthy air;
• a low CO2 value proves low particles, VOCs or mould risk;
• a purifier replaces ventilation or source control;
• a cool room is moisture-safe;
• one humidity number fits every room and mode;
• a short monitoring period proves long-term seasonal performance;
• the absence of visible mould proves the absence of hidden moisture;
• an environmental reading diagnoses a medical condition.

Unresolved questions

• Which operating targets are realistic for coastal, lowland and upland Bali sites without excessive energy or maintenance burden?
• How should sensor accuracy be handled during very high humidity?
• Which wardrobe and lock-up strategies remain reliable through long owner absence?
• What outdoor-air strategy best balances humidity, particles, noise, insects and energy for each micro-location?
• Which staff alerts lead to useful action rather than alarm fatigue?
• How should wet-season commissioning differ from opening tests conducted in a drier period?

Sources

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

1. WHO global air quality guidelines

   Authoritative guidance. Ambient pollutant benchmarks used as exposure context. Limit: A complete indoor residential specification or proof that an indoor environment is healthy.

2. WHO guidelines for indoor air quality: dampness and mould

   Authoritative guidance. Prevention and remediation of persistent dampness and microbial growth. Limit: A universal safe microbial threshold or proof that hidden mould is absent.

3. WHO guidelines for indoor air quality: selected pollutants

   Authoritative guidance. Pollutant-specific health context and source-control considerations. Limit: A complete residential specification or a single sensor score for indoor air quality.

4. ASHRAE position document on limiting indoor mold and dampness in buildings

   Authoritative guidance. Building moisture control and dampness prevention principles. Limit: A universal Bali project threshold or proof that a building is mould-free.

5. ASHRAE position document on indoor carbon dioxide

   Authoritative guidance. Use of indoor CO₂ as a limited ventilation indicator in context. Limit: Treating CO₂ as a complete indoor-air-quality or health score.

6. Low-cost air pollution monitors and indoor air quality

   Authoritative guidance. Capabilities and practical limits of lower-cost indoor monitors. Limit: Regulatory-grade accuracy, diagnosis or complete pollutant coverage.

7. Enhanced Air Sensor Guidebook

   Authoritative guidance. Planning, selecting and interpreting air-sensor measurements. Limit: Replacing calibrated professional instruments or inferring a medical outcome.

Related content

• Theme: Indoor environment and moisture
• Protocol: Indoor Environment and Moisture Control Protocol
• Methods Note: How DALLEAU reads evidence for private residences in Bali
• Methods Note: Why commissioning matters more than handover

Closing

Control the cause before interpreting the sensor

DALLEAU Atelier carries moisture and indoor-environment questions through the brief, MEP coordination, maintenance access, operating modes, commissioning and seasonal review.