Hot, cold, humid or draft complaints
Habitability & Environmental Quality · SERVICE 05
Onboard Thermal Comfort Survey
A cabin can meet a temperature setpoint and still feel uncomfortable. Air speed, humidity, radiant temperature, vertical temperature difference, clothing, activity and uneven distribution all influence how people experience the space. Vessel Doctor assesses these factors in occupied vessel areas and translates them into practical HVAC and habitability findings.
ENVIRONMENTAL QUALITYClear evidence→
VESSEL DOCTOROnboard Thermal Comfort Survey
SURVEY PROFILEHabitability & Environmental Quality
05/21
01
WHY THIS SURVEY MATTERS
Evidence before assumption.
Thermal complaints often move from one location to another when only thermostat settings are adjusted. Measurement helps identify insufficient airflow, excessive drafts, solar or machinery heat gain, poor diffuser balance, humidity problems and differences between cabins, decks or operating conditions.
02
MEASUREMENT SCOPE
What we measure.
- ✓Dry-bulb air temperature
- ✓Relative humidity
- ✓Air velocity and local drafts
- ✓Globe or mean radiant temperature where required
- ✓Vertical temperature gradient
- ✓Supply and return air conditions
- ✓PMV and PPD indices when the method and assumptions are appropriate
- ✓Space-to-space variation and HVAC operating status
03
TIMING & APPLICATION
When to request it.
Newbuilding accommodation trials
HVAC balancing or recommissioning
After cabin refurbishment or layout changes
Recurring condensation or uneven-temperature problems
Comfort-class or owner-specification verification
04
SURVEY PROCESS
A controlled route from plan to finding.
Define
Confirm the decision, vessel condition and evaluation basis.
Prepare
Agree locations, safe access, instruments and operating matrix.
Measure
Capture traceable data with conditions documented during measurement.
Interpret
Evaluate against the agreed basis and isolate meaningful patterns.
Report
Issue findings, limitations and focused next actions.
05
TECHNICAL DELIVERABLE
What you receive.
- ✓Space and measurement-point plan
- ✓Environmental and HVAC operating records
- ✓Thermal parameters and comfort indices where applicable
- ✓Identification of inconsistent or problematic spaces
- ✓Probable contributors and corrective recommendations
- ✓Retest plan after HVAC adjustments when requested
06
STANDARDS & PROJECT CRITERIA
The governing basis comes first.
Use applicable class habitability criteria, owner specifications and relevant editions of ISO 7726 and ISO 7730 or other contractually agreed thermal-comfort methods. Clearly document all clothing, activity and environmental assumptions used in PMV/PPD calculations.
Important
Explore our standards directory↗Acceptance remains subject to the applicable flag administration, classification society, contract, vessel specification and authorised reviewing party.
ASIA + WORLDWIDE ATTENDANCE
Onboard Thermal Comfort Survey wherever the vessel needs it.
Vessel Doctor coordinates this service for vessels in Singapore, India, Malaysia, Sri Lanka, Indonesia, Thailand, wider Asian maritime centres and ports worldwide. The scope can support technical managers, marine superintendents, ship agents, owners, operators, shipyards and consultants who need documented onboard evidence.
How clients describe this need: Projects may be described as ship thermal-comfort survey, onboard temperature and humidity test, vessel HVAC comfort assessment and cabin comfort measurement. Clients may also report that cabins or workspaces are too hot, cold, humid, uneven or drafty even when the thermostat appears normal. Depending on the technical question, the attendance may involve thermal testing, temperature and humidity measurement, airflow monitoring, HVAC assessment, comfort evaluation or troubleshooting during commissioning, sea trials, delivery acceptance, shipyard modifications or in-service complaint investigation. We confirm the final scope from the vessel, operating condition, access, applicable criteria, measurement purpose and required reporting outcome.
Southeast AsiaOnboard Thermal Comfort Survey in Singapore↗South AsiaOnboard Thermal Comfort Survey in India↗Southeast AsiaOnboard Thermal Comfort Survey in Malaysia↗South AsiaOnboard Thermal Comfort Survey in Sri Lanka↗Southeast AsiaOnboard Thermal Comfort Survey in Indonesia↗Southeast AsiaOnboard Thermal Comfort Survey in Thailand↗Global coverageWorldwide Onboard Thermal Comfort Survey↗
SERVICE FAQ
Questions project teams ask.
Every scope is confirmed against the actual vessel, timing and decision requirement.
01Is temperature alone enough to assess comfort?+
No. Humidity, air speed, radiation, activity and clothing can change comfort even at the same air temperature.
02Can the survey identify poor HVAC balancing?+
It can reveal uneven conditions and airflow indicators. Detailed testing, adjusting and balancing may require additional duct and system measurements.
03Should the vessel be occupied during testing?+
Representative occupancy and operating loads are preferable where practical because people and equipment affect the heat balance.
04Can thermal comfort be combined with IAQ?+
Yes. Combining both surveys often provides a more complete assessment of accommodation performance.
THERMAL-CONDITION TEST PLAN
Match the measurement window to the heat-load question.
A cabin that is hot, cold, humid, uneven or drafty needs more than one spot temperature. A defensible onboard thermal-comfort assessment records the occupied zone, HVAC state, weather and vessel heat loads together, then separates air temperature, radiation, humidity, air movement, clothing and activity before recommending a change.
Define the complaint
Identify who is uncomfortable, in which space, at what time and under which voyage, machinery, solar, occupancy and ventilation condition.
Hold a representative state
Record outdoor conditions, HVAC mode and setpoints, doors, occupancy, lighting, equipment, machinery load and sufficient stabilisation time.
Measure the occupied zone
Use agreed heights and locations to capture air and radiant temperature, humidity, air speed, vertical difference and supply/return evidence where relevant.
Separate comfort from balancing
Compare spaces and operating states, document PMV/PPD assumptions where used and identify whether comfort evidence, HVAC testing or both are needed next.
| Vessel question | Evidence to capture | Decision boundary |
|---|---|---|
| Cabin is hot although the thermostat meets its setpoint | Occupied-zone air and globe/radiant temperature, humidity, air speed, supply/return conditions, solar orientation, adjacent machinery or service-space load and a comparable unaffected cabin. | Temperature alone cannot separate air-distribution, radiant, humidity and occupancy causes. |
| Crew report a cold draft near a bunk, desk or bridge position | Local air speed and direction, turbulence or variability where required, vertical temperature difference, diffuser position, HVAC state, clothing and activity at the occupied point. | A room-average reading can miss a local draft or vertical discomfort problem. |
| Some cabins or decks are comfortable while others are not | Repeatable grid or representative-point measurements, zone/damper state, supply and return air evidence, doors, occupancy and matching time/weather conditions. | Thermal comfort mapping can identify the pattern; detailed duct balancing requires a separate airflow scope. |
| Humidity, condensation or clammy conditions recur | Relative humidity, air and relevant surface temperatures, dew-point context, outdoor air, infiltration indicators, HVAC operating history and timing of the event. | Comfort evidence does not replace a moisture-source, mould or indoor-air-quality investigation when those questions are present. |
| Support owner, yard, class or flag review during commissioning or sea trial | Named criterion and standard edition, agreed spaces, occupancy and operating matrix, instrument capability, calibration evidence, environmental assumptions, raw results and deviations. | Project-specific report acceptance is not blanket class, flag or supplier approval. |
Current measurement and evaluation references
ISO 7726:2025 specifies instrument characteristics and methods for measuring physical quantities in a thermal environment. ISO 7730:2025 addresses analytical evaluation of general and local thermal comfort, including PMV and PPD. The contract, vessel specification, class notation or owner requirement can call for a different edition or method, so the governing basis and every clothing, activity and environmental assumption must be agreed before interpretation.
Information needed before mobilisation
Send the vessel and IMO number, affected rooms and complaint timing, voyage or berth condition, outdoor climate, HVAC drawings and zones, supply/return layout, setpoints and operating mode, machinery and galley loads, occupancy, recent changes, relevant owner/class/flag criteria, available previous results and the decision deadline. Attendance can be assessed for commissioning, sea trial, delivery, shipyard modification and in-service investigation in Singapore, Malaysia, India, Sri Lanka, Indonesia, Thailand, the Philippines, the Middle East, Asia-Pacific and worldwide.
Class and flag context
For ABS-, BV-, CCS-, CRS-, DNV-, IRS-, KR-, LR-, ClassNK-, PRS-, RINA- or Türk Loydu-classed vessels, including Singapore-flagged and other internationally registered ships, confirm the habitability notation, measurement condition, witnessing and report route with the owner, yard and attending surveyor. No class, flag or statutory approval is claimed.
START A TECHNICAL DISCUSSION
Plan your onboard thermal comfort survey.
Share the vessel, location, operating condition and reporting purpose. We will help shape a focused, technically defensible survey scope.