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Marine HVAC: Heating, Ventilation and Air Conditioning Systems

Marine HVAC (Heating, Ventilation and Air Conditioning) systems provide controlled environmental conditions throughout the ship including accommodation, bridge, public spaces, machinery spaces, cargo holds, and specialised spaces (galley, laundry, hospital, battery rooms, paint stores). The HVAC architecture typically includes central air handling units (AHUs) generating conditioned air for distribution through ductwork to fan coil units (FCUs) at terminal points; chilled water plant providing cold water for cooling (covered in marine refrigeration); hot water or steam for heating from the auxiliary boiler; control systems automating temperature, humidity and ventilation; specialised systems for galley exhaust, laundry, hospital areas, smoking rooms, and battery rooms; and the integration with smoke control under SOLAS Chapter II-2 fire safety. Modern ships face HVAC challenges from increasingly stringent crew comfort standards (ISO 7547 thermal comfort), cruise ship passenger expectations, energy efficiency requirements under CII and FuelEU Maritime, and decarbonisation pressures driving heat recovery and electric integration. ShipCalculators.com hosts the principal computational tools for marine HVAC: the HVAC accommodation cooling load calculator, the HVAC air change rate calculator, the HVAC CO2 buildup calculator, the HVAC cooling load calculator, the HVAC dew point calculator, the HVAC galley exhaust rate calculator, the HVAC psychrometrics calculator, the HVAC sensible heat ratio calculator, and the HVAC ventilation rate calculator.

Contents

Background

HVAC functions on ships

Marine HVAC serves multiple functions:

  • Thermal comfort: maintaining accommodation temperature 20-26 C and humidity 30-60 percent for crew and passengers.
  • Air quality: providing fresh air at adequate rate, removing CO2, odours, and contaminants.
  • Smoke control: limiting smoke spread during fire (SOLAS Chapter II-2 Regulation 8).
  • Cargo protection: ventilating cargo holds for moisture management.
  • Equipment cooling: ventilating machinery spaces, electrical equipment rooms.
  • Hazardous space ventilation: battery rooms (hydrogen), paint stores (solvents), galley (combustibles).
  • Special atmospheres: pressurised refuge spaces, engine emergency room.

HVAC zones

Ship HVAC typically uses zoned architecture:

  • Accommodation main zone: cabins, public spaces, corridors.
  • Galley and laundry: high humidity and combustion products.
  • Bridge: high-precision climate control for navigation electronics.
  • Public spaces: restaurants, theatres, casinos (passenger ships).
  • Engine room: high heat load, ventilation rather than air conditioning.
  • Cargo holds: ventilation control for moisture and cargo conditions.
  • Hazardous spaces: dedicated ventilation with explosion-proof equipment.

Each zone has independent air handling and control.

Major manufacturers

Marine HVAC manufacturers:

  • Heinen & Hopman (Netherlands): widely used on cruise ships and passenger vessels.
  • Carrier Transicold (Marine): container reefer and HVAC.
  • Daikin (Marine): VRF and chilled water systems.
  • Frigomar: smaller ship HVAC specialist.
  • Climma (Veco): yacht and small ship HVAC.

Air handling and distribution

Air handling units (AHUs)

Air handling units:

  • Mixed air section: combining fresh air and recirculated air.
  • Filter section: typically G3 to F7 grade for accommodation, higher for medical areas.
  • Cooling coil: chilled water from refrigeration plant.
  • Heating coil: steam from auxiliary boiler or hot water.
  • Humidifier: in cold-climate operations.
  • Fan: typically VFD-controlled for variable air volume.
  • Sound attenuator: reducing fan noise.

Ductwork

Ductwork distribution:

  • Supply duct: from AHU to terminal points.
  • Return duct: from spaces back to AHU.
  • Fresh air duct: from external intake.
  • Exhaust duct: to atmospheric discharge.
  • Galley exhaust: separate duct with grease management.
  • Laundry exhaust: separate duct with lint management.

Fire and smoke dampers

Fire and smoke dampers (under SOLAS Chapter II-2):

  • Fire dampers: closing on fire detection or thermal trigger; typically at A-class division penetrations.
  • Smoke dampers: closing on smoke detection.
  • Remote operation: from bridge or fire control panel.
  • Manual operation: by accessible release.
  • Type approval: required under FTP Code.

Cooling load calculation

Cooling load components

Cooling load components:

  • Sensible heat from people: typically 75 to 110 W per person.
  • Sensible heat from lighting: typical 10 to 20 W/m² for accommodation.
  • Sensible heat from equipment: variable by space.
  • Latent heat: from people (moisture from breathing) and from cooking, showering, etc.
  • Solar gain: through windows on weather decks.
  • Conduction through walls: from external air or adjacent spaces.
  • Ventilation load: cooling/dehumidifying fresh air to space conditions.

The total cooling load is the sum of these components plus margin. The HVAC cooling load calculator implements the standard calculation.

ISO 7547 ship comfort

ISO 7547 specifies thermal comfort criteria for ships:

  • Temperature: 22 to 27 C in summer, 20 to 24 C in winter.
  • Humidity: 30 to 70 percent.
  • Air velocity: 0.15 to 0.25 m/s in occupied zone.
  • Operative temperature: integrating air temperature and surface temperatures.

Crew comfort under ISO 7547 supports productivity and reduces complaints.

Sensible heat ratio

Sensible Heat Ratio (SHR):

  • Definition: sensible cooling load / total cooling load.
  • Typical values: 0.7 to 0.85 for accommodation, lower (down to 0.5) for high-latent spaces (galleys, swimming pool areas).
  • Equipment selection: SHR drives chilled water temperature, coil rows, and bypass factor selection.

The HVAC sensible heat ratio calculator addresses this.

Ventilation requirements

Air change rate

Air change rate requirements:

  • Cabins: 6 to 8 air changes per hour (ACH).
  • Public spaces: 8 to 15 ACH depending on occupancy density.
  • Smoking rooms: 15 to 20 ACH.
  • Galley: 25 to 40 ACH (high to capture cooking emissions).
  • Engine room: variable, primarily for combustion air supply with comfort secondary.
  • Battery rooms: continuous ventilation maintaining hydrogen below 1 percent (10,000 ppm).

The HVAC air change rate calculator addresses sizing.

Fresh air rate

Fresh air rate per occupant (ASHRAE standard reference):

  • Accommodation: 7.5 to 10 L/s per person.
  • Public spaces: 7.5 to 12.5 L/s per person.
  • Galleys: based on cooking equipment rather than occupancy.

The fresh air rate ensures CO2 control and odour management. The HVAC ventilation rate calculator and HVAC CO2 buildup calculator address compliance.

Specialised ventilation

Specialised ventilation:

  • Galley hood: high-volume exhaust above cooking equipment with grease filters.
  • Laundry exhaust: high-volume with lint filters and heat recovery.
  • Hospital ventilation: separate system to prevent cross-contamination.
  • Smoking rooms: dedicated exhaust with carbon filters.
  • Battery rooms: continuous mechanical ventilation with hydrogen detection.
  • Paint stores: continuous mechanical ventilation with explosion-proof equipment.

Each space has specific provisions in the ship’s HVAC design.

Specialised spaces

Galley exhaust

Galley exhaust:

  • Hood: above cooking equipment, sized for capture.
  • Grease filter: removing grease aerosols.
  • Duct: separate galley exhaust duct, typically of stainless steel.
  • Fan: high-pressure fan handling grease-laden air.
  • Discharge: separate stack at safe location.
  • Fire suppression: required by SOLAS Chapter II-2 for galley fat-fryer.

The HVAC galley exhaust rate calculator addresses sizing.

Engine room ventilation

Engine room ventilation:

  • Combustion air: large quantity for engine combustion.
  • Cooling air: removing engine room heat.
  • Hot air discharge: typically through stack with temperature management.
  • Fresh air supply: separate intakes.
  • Fan capacity: typically 50 to 200 air changes per hour.

Hospital ventilation

Hospital areas (sick bay, isolation rooms):

  • Separate HVAC: not connected to general accommodation HVAC.
  • HEPA filters: high-efficiency air filtration.
  • Negative pressure for isolation rooms.
  • Independent exhaust: through separate duct.

Battery room ventilation

Battery room ventilation:

  • Continuous mechanical ventilation: maintaining hydrogen below 1 percent.
  • Explosion-proof equipment: certified electrical fittings.
  • Gas detection: with alarm and automatic emergency ventilation increase.
  • Specific air change rate: based on battery type and capacity.

For lithium-ion battery installations, additional considerations apply due to thermal runaway risk.

Heat recovery and energy efficiency

Heat recovery ventilation (HRV)

Heat recovery ventilation:

  • Counter-flow heat exchanger: between supply and exhaust air streams.
  • Effectiveness: 60 to 80 percent typical for sensible heat recovery.
  • Energy savings: substantial in cold climates.
  • Frost protection: in extreme cold.

Energy recovery ventilation (ERV)

Energy recovery ventilation:

  • Latent and sensible recovery: through enthalpy wheel or membrane exchanger.
  • Effectiveness: 50 to 75 percent for combined recovery.
  • Application: in tropical and humid climates.

Variable refrigerant flow (VRF)

Variable refrigerant flow systems:

  • Multi-zone VRF: single outdoor unit with multiple indoor evaporators.
  • Heat recovery VRF: simultaneously cooling some zones and heating others.
  • High efficiency: through variable-speed compressor.
  • Used on: smaller ships, yachts, retrofits.

Free cooling

Free cooling using cold seawater:

  • Direct exchange: seawater cooling chilled water without compressor operation.
  • Conditions: when seawater temperature is below required chilled water supply.
  • Polar service: extensive opportunity for free cooling.
  • Energy savings: substantial when applicable.

Smoke control and fire safety

SOLAS II-2 ventilation provisions

SOLAS Chapter II-2 ventilation provisions:

  • Mechanical ventilation shutdown: capability of shutting down from outside the space.
  • Fire dampers: at A-class division penetrations.
  • Smoke dampers: at MVZ boundaries.
  • Stair pressurisation: on passenger ships maintaining positive pressure.
  • Smoke extraction: from atriums and large public spaces.

Smoke spread limitation

Smoke spread limitation:

  • Damper closure on fire alarm prevents smoke movement through ducts.
  • Fan shutdown prevents smoke active distribution.
  • Compartment isolation through HVAC zoning.
  • Pressurisation of escape routes maintains them smoke-free.

The HVAC system is integral to fire safety performance.

Operational considerations

Routine operation

Routine HVAC operation:

  • Continuous operation during occupancy.
  • Setback during low-occupancy periods.
  • Filter changes: based on differential pressure or scheduled.
  • Coil cleaning: periodic for performance maintenance.
  • Fan belt and bearing: routine maintenance.
  • Condensate drainage: from cooling coils.
  • Control system: continuous monitoring of operating parameters.

Crew comfort complaints

Crew comfort complaints typically about:

  • Temperature: too hot or too cold despite design specifications.
  • Humidity: too dry or humid.
  • Drafts: from poorly designed terminal devices.
  • Noise: from fans and ductwork.
  • Air quality: stale air, unpleasant odours.

Addressing comfort complaints requires diagnosis of root cause (control set-point, equipment performance, duct leakage, etc.) and correction.

Energy management

Energy management:

  • Demand-based control: reducing flow or temperature when not occupied.
  • Heat recovery: from exhaust to supply.
  • Free cooling: using cold seawater when possible.
  • Equipment efficiency: VFD on fans, efficient motors.
  • Insulation: of ducts and chilled water lines.

The energy management contributes to CII rating and overall ship efficiency.

Future developments

Decarbonisation

Decarbonisation in HVAC:

  • Lower-GWP refrigerants: in connection with refrigeration plant.
  • Heat pumps: reversible refrigeration cycles for both heating and cooling.
  • Heat recovery: progressive improvements.
  • Smart controls: learning systems optimising operation.

Crew wellness

Crew wellness focus:

  • ISO 7547 compliance: with substantial margin.
  • Air quality monitoring: VOC, particulates, CO2.
  • Personalised control: in cabins.
  • Biophilic design: integrating with general accommodation comfort.

Digital twins

Digital twins of HVAC systems:

  • Real-time simulation: of HVAC performance.
  • Predictive maintenance: based on operational data.
  • What-if analysis: for retrofit decisions.

See also

References

  • ISO 7547 Air-conditioning and ventilation of accommodation spaces in ships.
  • ASHRAE Handbook (Fundamentals, HVAC Systems and Equipment).
  • IMO MSC.1/Circ.1503 and successors on bridge ergonomics.
  • SOLAS Chapter II-2 ventilation provisions.
  • IACS Common Structural Rules.
  • Class society marine HVAC rules.