AHU

Double Skin AHU

October 6, 2026 11 Min Read

Double Skin AHU: Construction, Components & Applications

A Double Skin AHU (Air Handling Unit) is an air-handling system constructed with two layers of casing separated by an insulated internal space or panel. Compared with a basic single-skin configuration, double-skin construction can provide improved thermal insulation, structural strength, condensation control, acoustic performance and durability when properly designed.

Double Skin AHUs are widely considered for applications where the HVAC system requires robust casing construction and controlled air-treatment conditions.

They can be used in:

Pharmaceutical facilities
Hospitals
Cleanrooms
Manufacturing plants
Chemical industries
Textile industries
Food-processing plants
Hotels
Shopping malls
Corporate offices
Laboratories
Industrial buildings

VIPUL HVAC SOLUTION PVT. LTD. offers AHU configurations including double-skin and single-skin construction, pre/fine/HEPA filtration, cooling and heating coils, backward-curved and EC fans, acoustic insulation, BMS-ready controls and treated fresh-air handling units. Vipulhvac Solution

What Is a Double Skin AHU?

A Double Skin AHU is an Air Handling Unit whose casing uses an inner and outer skin with insulation between them.

A simplified construction is:

Outer Skin → Insulation → Inner Skin → Conditioned Air

The insulation separates the internal air stream from the external environment and helps reduce unwanted heat transfer.

The exact construction varies according to:

AHU size
Airflow
Static pressure
Indoor/outdoor installation
Temperature
Humidity
Filtration
Acoustic requirements
Hygiene requirements
Project specifications

Modern modular double-skin AHUs can use insulated panels and thermal-break construction. For example, Daikin’s published double-skin AHU documentation describes aluminum framing, insulated panels and thermal-barrier construction designed to reduce heat loss and condensation. Daikin

What Is the Difference Between Single Skin and Double Skin AHU?

The main difference is the casing construction.

Feature	Single Skin AHU	Double Skin AHU
Casing layers	Single	Two
Insulation	Limited/configuration dependent	Integrated between skins
Thermal protection	Moderate	Generally better
Condensation control	Application dependent	Better potential
Structural rigidity	Application dependent	Generally robust
Acoustic performance	Basic/configuration dependent	Can be improved
Hygiene applications	Selected applications	Commonly considered
Industrial applications	Yes	Excellent
Initial cost	Usually lower	Usually higher
Long-term thermal performance	Depends on construction	Generally advantageous

The correct choice should be based on the HVAC application’s technical requirements rather than price alone.

Double Skin AHU Construction

A typical Double Skin AHU can be constructed using several major elements.

1. Outer Skin

The external panel forms the protective surface of the AHU.

It protects the internal insulation and components from the surrounding environment.

Common construction materials can include:

Galvanized steel
Pre-painted steel
Stainless steel
Aluminum

The material should be selected according to the environment and project requirements.

2. Inner Skin

The inner panel faces the air stream.

It should provide a suitable internal surface for:

Airflow
Cleaning
Maintenance
Filtration sections
Coil sections
Fan sections

For hygiene-sensitive applications, the internal surface may require special construction and finishing.

3. Insulation

Insulation is one of the most important components of a double-skin AHU.

Depending on the manufacturer’s design, insulation may use materials such as:

PU/PIR
Mineral wool
Other approved thermal/acoustic insulation materials

Insulation helps reduce heat transfer between the conditioned air and surrounding environment.

It can also contribute to condensation control and acoustic performance.

Daikin’s double-skin AHU documentation, for example, describes PU-insulated panels and additional frame insulation as part of its construction. Daikin

4. AHU Frame

The frame provides structural support for the AHU casing and internal components.

A modular AHU may use an aluminum or other engineered structural frame.

The frame must be capable of supporting:

Panels
Filters
Coils
Fans
Motors
Dampers
Access doors
Internal accessories

5. Thermal Break

A thermal-break design can reduce direct thermal bridges through the AHU frame.

This is particularly useful when:

Indoor air is cold
Outdoor temperature is high
Humidity is high
Condensation is a concern

A properly designed thermal barrier can improve casing thermal performance.

Major Components of a Double Skin AHU

A Double Skin AHU is more than an insulated box. It is a complete air-treatment assembly.

Typical components include:

Air Intake Section

Introduces outdoor air into the AHU where required.

Dampers

Control:

Fresh air
Return air
Exhaust air
Mixed air

Pre-Filters

Capture larger particles and protect downstream components.

Fine Filters

Provide higher levels of particulate filtration.

HEPA Filters

Can be incorporated for applications requiring high-efficiency filtration.

Cooling Coil

Cools incoming or recirculated air and can provide dehumidification.

Heating Coil

Provides heating where required.

Supply Fan

Moves conditioned air through the duct system.

Motor

Drives the supply fan.

VFD

Allows fan-speed control where specified.

Drain Pan

Collects condensate produced by the cooling coil.

Sensors

Can monitor:

Temperature
Humidity
Pressure
Differential pressure
Airflow

Control Panel

Controls AHU operation.

BMS Interface

Allows the AHU to communicate with a Building Management System where required.

VIPUL HVAC’s published AHU specifications include pre-, fine- and HEPA-filtration options, cooling/heating coils, backward-curved and EC fans, acoustic insulation and BMS-ready controls. Vipulhvac Solution

How Does a Double Skin AHU Work?

The working principle depends on the AHU configuration, but a typical chilled-water system operates approximately as follows:

Outdoor/Return Air
Dampers
Pre-Filter
Fine Filter
Cooling Coil
Supply Fan
Supply Duct
Conditioned Space
Return Air

The double-skin casing surrounds the internal components and provides thermal and structural protection.

For a fresh-air configuration, the system may instead operate as:

Outdoor Air → Filters → Cooling/Heating → Fan → Fresh-Air Duct → Building

The exact airflow arrangement should be determined by the HVAC design.

7 Major Benefits of Double Skin AHU

1. Better Thermal Insulation

The insulated double-wall construction can reduce unwanted heat transfer between the conditioned air and the surrounding environment.

This is especially useful for AHUs operating in hot or humid environments.

2. Improved Condensation Control

Condensation can occur when a cold AHU surface comes into contact with warm, humid air.

Appropriate insulation and thermal-break construction can help reduce the risk of surface condensation.

However, condensation control also depends on:

Insulation thickness
Thermal bridges
Air leakage
Surface temperature
Ambient humidity
Installation quality

3. Robust Construction

Double-skin construction can provide a strong and durable enclosure for industrial HVAC equipment.

This is useful where the AHU operates continuously or in demanding environments.

4. Better Acoustic Performance

The insulated casing can help reduce transmission of fan and airflow noise.

For noise-sensitive applications, additional acoustic treatment may be incorporated.

Examples include:

Acoustic insulation
Sound attenuators
Low-noise fans
Vibration isolation

5. Better Protection of Internal Components

The casing protects internal HVAC components from the surrounding environment.

This can help protect:

Filters
Coils
Fans
Motors
Sensors
Controls

6. Suitable for Specialized HVAC Applications

Double Skin AHUs can be configured for applications requiring:

High filtration
Temperature control
Humidity control
Fresh-air handling
Pressure management
Cleanable internal surfaces
BMS integration

7. Flexible Customization

A double-skin AHU can be engineered around project-specific requirements.

Possible customization includes:

CFM
Casing dimensions
Insulation
Filters
Coil capacity
Fan selection
Static pressure
Access doors
Controls
BMS
Fresh-air percentage

VIPUL HVAC specifically publishes customized CFM requirements and double-/single-skin AHU construction as part of its AHU offering. Vipulhvac Solution

Double Skin AHU Applications

1. Pharmaceutical Industry

Pharmaceutical HVAC systems can require controlled:

Temperature
Humidity
Airflow
Filtration
Pressure
Cleanliness

Double Skin AHUs can be configured with appropriate filtration, coils, controls and hygienic features according to the project requirements.

2. Cleanrooms

Cleanrooms require carefully controlled environmental conditions.

A Double Skin AHU can be configured with:

Pre-filtration
Fine filtration
HEPA filtration
Cooling coil
Heating coil
Humidity control
Pressure control
BMS monitoring

The final design should be based on the required cleanroom classification and process requirements.

3. Hospitals

AHUs are widely used for centralized ventilation and air-conditioning in healthcare facilities.

Depending on the room application, the system may require:

Fresh-air treatment
Filtration
Temperature control
Humidity management
Pressure control

Double Skin AHUs can be considered where enhanced casing construction and insulation are required.

4. Chemical Industries

Chemical manufacturing environments may have demanding HVAC conditions.

The AHU design may need to consider:

Temperature
Humidity
Dust
Process heat
Ventilation
Corrosive environments
Filtration

Material selection becomes particularly important where corrosive contaminants may be present.

5. Textile Industries

Textile facilities can have specific environmental requirements involving:

Temperature
Relative humidity
Airflow
Dust

Double Skin AHUs can be integrated into centralized textile HVAC systems according to the production process.

6. Food Processing Plants

Food-processing facilities may require controlled:

Temperature
Humidity
Filtration
Ventilation
Air cleanliness

Double Skin AHUs can be customized according to the facility’s hygiene and HVAC requirements.

7. Hotels and Commercial Buildings

Double Skin AHUs can be used in:

Hotels
Shopping malls
Corporate offices
Business centers
Large retail buildings
Convention facilities

They can provide centralized air treatment and distribution.

8. Industrial Manufacturing Plants

Industrial AHUs may operate for extended hours and under challenging environmental conditions.

Double Skin construction can provide a robust casing for applications involving:

Large airflow
High static pressure
Continuous operation
Specialized filtration
Process cooling
Fresh-air ventilation

Double Skin AHU for Fresh Air Applications

A Double Skin AHU can be configured as a Fresh Air AHU or Treated Fresh Air Unit.

Typical arrangement:

Outdoor Air → Damper → Pre-Filter → Fine Filter → Cooling Coil → Fan → Supply Duct

Fresh-air applications may require:

High filtration
Cooling
Dehumidification
Heating
Humidity control
Pressure control

VIPUL HVAC’s published AHU range includes treated fresh-air handling units as well as single- and double-skin construction. Vipulhvac Solution

Double Skin AHU Filtration

Filtration should be selected according to the application.

Pre-Filter

Captures larger particles.

Fine Filter

Provides additional particulate filtration.

HEPA Filter

Used where high-efficiency particulate filtration is required.

For pharmaceutical, healthcare and cleanroom applications, filtration design should be coordinated with the overall HVAC and air-quality strategy.

The filter pressure drop should also be considered during fan selection.

Double Skin AHU Cooling Coil

The cooling coil is responsible for transferring heat from the air to the cooling medium.

A chilled-water system typically operates as:

Chiller → Chilled Water → AHU Cooling Coil → Conditioned Air

The coil should be selected based on:

Airflow
Entering-air temperature
Leaving-air temperature
Cooling capacity
Chilled-water temperature
Water flow
Face velocity
Pressure drop

Correct coil selection is important for both performance and energy efficiency.

Double Skin AHU Fan Selection

The fan must overcome the total system resistance.

This includes pressure losses from:

Filters
Coils
AHU casing
Dampers
Ductwork
Diffusers
Sound attenuators
Other accessories

Fan options can include:

Backward-curved fans
EC fans
Plug fans

VIPUL HVAC publishes backward-curved and EC fan options for its AHU systems. Vipulhvac Solution

Double Skin AHU Controls

Modern AHUs can incorporate sophisticated control systems.

Typical controls include:

Temperature Control

Maintains the required supply or room temperature.

Humidity Control

Controls relative humidity where required.

Fan-Speed Control

VFDs or EC motors can modulate fan operation.

Filter Monitoring

Differential-pressure sensors can indicate filter loading.

Coil Control

Control valves can regulate chilled-water or heating-water flow.

BMS Integration

The AHU can communicate operating conditions and alarms to a central Building Management System.

Double Skin AHU Installation

Proper installation is essential for achieving the expected AHU performance.

Installation may include:

Foundation/support preparation
AHU positioning
Leveling
Module alignment
Panel inspection
Duct connection
Chilled-water connection
Condensate drain connection
Electrical connection
Control wiring
Sensor installation
Insulation inspection
Fan alignment
Testing

Improper installation can create:

Air leakage
Vibration
Noise
Condensation
Poor drainage
Reduced airflow

Double Skin AHU Testing & Commissioning

After installation, the HVAC system should be tested.

Important checks can include:

Fan rotation
Motor current
Airflow
Static pressure
Supply-air temperature
Return-air temperature
Coil performance
Filter pressure drop
Drainage
Vibration
Noise
Damper operation
Control operation

Air balancing should then be performed according to the approved design.

VIPUL HVAC’s published AHU project approach includes installation, testing, air balancing and commissioning. Vipulhvac Solution

Double Skin AHU Maintenance

Preventive maintenance can help extend equipment life and maintain performance.

A maintenance program should include:

Filter inspection
Filter replacement
Coil cleaning
Fan inspection
Motor inspection
Bearing inspection
Belt inspection where applicable
Drain-pan cleaning
Condensate drain inspection
Damper inspection
Sensor checking
Electrical inspection
Vibration monitoring
Airflow measurement
Insulation inspection

The internal AHU surfaces should also be inspected for:

Corrosion
Dirt accumulation
Water leakage
Insulation damage
Seal deterioration

How to Choose a Double Skin AHU

Before purchasing a Double Skin AHU, consider the following parameters.

1. Airflow

Determine the required CFM or m³/h.

2. Cooling Capacity

Calculate the required sensible and latent cooling load.

3. Static Pressure

Calculate the complete external and internal pressure losses.

4. Filtration

Select appropriate pre-, fine- and HEPA filters where required.

5. Insulation

Select appropriate insulation according to thermal and environmental requirements.

6. Casing Material

Choose the appropriate material based on the operating environment.

7. Fan

Select the fan according to airflow, pressure, efficiency and noise.

8. Controls

Determine whether VFD, sensors and BMS integration are required.

9. Maintenance Access

Ensure sufficient access to:

Filters
Coils
Fans
Motors
Controls

10. Installation Environment

Consider whether the AHU will be installed:

Indoors
Outdoors
On a rooftop
In a plant room

Double Skin AHU Cost

The price of a Double Skin AHU depends on the complete technical specification.

Important cost factors include:

CFM
Casing dimensions
Panel construction
Insulation
Material
Cooling capacity
Heating capacity
Fan
Motor
Static pressure
Filters
HEPA filtration
Controls
VFD
BMS
Accessories
Installation
Ductwork
Piping

For example, two AHUs with identical airflow may have very different prices if one requires pharmaceutical-grade filtration, higher insulation, stainless-steel construction or advanced controls.

Therefore, AHU cost should be compared using a detailed technical specification rather than only CFM and price.

Why Choose VIPUL HVAC SOLUTION PVT. LTD.?

VIPUL HVAC SOLUTION PVT. LTD. provides AHU and complete HVAC engineering solutions for industrial, commercial and institutional projects.

Its published AHU capabilities include:

Double Skin AHUs
Single Skin AHUs
Customized CFM
Pre-filters
Fine filters
HEPA filters
Cooling coils
Heating coils
Backward-curved fans
EC fans
Acoustic insulation
BMS-ready controls
Treated Fresh Air Handling Units
Air washers
Duct and air-distribution design
Installation
Testing
Commissioning
Maintenance Vipulhvac Solution

Complete HVAC Project Support

HVAC Design → Load Calculation → AHU Selection → Double Skin AHU Supply → Ductwork → Piping → Installation → Testing → Air Balancing → Commissioning → AMC

This project-based approach helps ensure that the AHU is properly integrated with the complete HVAC system.

Frequently Asked Questions

What is a Double Skin AHU?

A Double Skin AHU is an Air Handling Unit constructed with inner and outer casing layers with insulation between them to improve thermal and structural performance.

What is the main advantage of a Double Skin AHU?

The major advantage is its insulated double-wall construction, which can improve thermal insulation, condensation control, durability and acoustic performance depending on the design.

What insulation is used in Double Skin AHUs?

Depending on the manufacturer and project, materials such as PU/PIR, mineral wool or other suitable thermal/acoustic insulation can be used.

Is Double Skin AHU better than Single Skin AHU?

Not necessarily for every application. Double Skin AHUs are generally preferred when stronger casing, insulation and environmental performance are important. Single-skin construction may be suitable for simpler applications.

Are Double Skin AHUs suitable for pharmaceutical plants?

Yes. They can be configured with appropriate filtration, cooling, heating, humidity and pressure-control features for pharmaceutical applications.

Can HEPA filters be installed in a Double Skin AHU?

Yes. HEPA filtration can be incorporated where required by the application.

Can a Double Skin AHU be used as a Fresh Air AHU?

Yes. A Double Skin AHU can be configured for fresh-air treatment and can include appropriate filtration, cooling, heating and humidity-control systems.

Can Double Skin AHUs connect to a chiller?

Yes. Chilled-water Double Skin AHUs can use chilled water from a central chiller plant through the AHU cooling coil.

Does a Double Skin AHU require maintenance?

Yes. Regular filter, coil, fan, motor, drain, sensor and control-system maintenance is important for reliable performance.

Does VIPUL HVAC supply Double Skin AHUs?

Yes. VIPUL HVAC’s published AHU range includes double-skin and single-skin configurations, customized CFM, filtration, coils, fans, controls and treated fresh-air solutions. Vipulhvac Solution

Conclusion

A Double Skin AHU provides an insulated and robust casing configuration for air-handling applications where thermal performance, condensation control, durability and controlled air treatment are important.

Its construction typically consists of:

Outer Skin + Insulation + Inner Skin + Structural Frame + HVAC Components

The AHU can then be configured with:

Filters + Cooling Coil + Heating Coil + Fan + Dampers + Sensors + Controls + BMS

Double Skin AHUs are suitable for a wide range of applications, including pharmaceutical plants, cleanrooms, hospitals, chemical industries, manufacturing plants, textile facilities, food-processing plants, hotels and commercial buildings.

The correct AHU should always be selected according to airflow, cooling load, static pressure, filtration, temperature, humidity, installation environment and maintenance requirements.

Need a Double Skin AHU for Your Project?

VIPUL HVAC SOLUTION PVT. LTD.

📞 Call: +91 8000392000