The Pros and Cons of Different Ductwork Materials.

When it comes to designing and installing a ventilation system, selecting the right ductwork material is crucial. The choice of material affects not only the efficiency and performance of the system but also its durability and maintenance requirements.

In this article, we will explore the pros and cons of different ductwork materials commonly used in domestic and commercial settings. By understanding the advantages and drawbacks of each option, you can make an informed decision that suits your specific needs.


Sheet Metal Ductwork.

Sheet metal, typically made from galvanized steel or aluminium, is one of the most popular choices for ductwork. There are various pros and cons for this material..


Durability: Sheet metal ducts are highly durable and resistant to damage, making them ideal for long-term use.

Fire Resistance: They offer excellent fire resistance, minimising the risk of fire spread within the ventilation system.

Efficient Airflow: Sheet metal provides smooth surfaces that promote efficient airflow, reducing resistance and energy consumption.

Customisable: They can be fabricated to meet specific design requirements, such as accommodating tight spaces or unusual layouts.


Cost: Sheet metal ducts tend to be more expensive compared to other materials, mainly due to the cost of the metal itself and the labour-intensive installation process.

Susceptible to Corrosion: If not properly protected or maintained, sheet metal ducts can corrode over time, compromising their structural integrity.

Difficult to Modify: Once installed, it can be challenging to modify sheet metal ducts, requiring professional assistance for any changes or additions.


Where is sheet metal ductwork utilised?

A popular application of sheet metal ductwork is in commercial buildings, where its durability and fire resistance are highly valued. Imagine a commercial building with a centralised HVAC system. The ductwork begins at the main air handling unit (AHU) located in the mechanical room. The AHU is responsible for conditioning the air and supplying it to different areas of the building.

From the AHU, a large rectangular sheet metal duct, known as the main supply duct, extends through the ceiling or crawlspace. This main supply duct branches off into smaller rectangular or round ducts that distribute air to specific zones or rooms.

For instance, a rectangular sheet metal duct extends from the main supply duct to a conference room on the first floor. This branch duct connects to an adjustable damper that regulates the airflow into the room. The branch duct then splits into multiple smaller round ducts using a duct splitter or take-off. These smaller round ducts are known as branch ducts and deliver conditioned air to individual supply registers or diffusers in the conference room.

On the return side of the system, another set of sheet metal ductwork is responsible for extracting air from the conditioned space and returning it to the AHU for reconditioning. Return air ducts typically run parallel to supply ducts, allowing air to flow back to the AHU. Return air grilles or registers are strategically placed throughout the building to facilitate the return of air to the system.

To ensure efficient airflow and prevent air leaks, sheet metal ducts are constructed using galvanized steel or aluminium. The ductwork is fabricated by cutting, bending, and fastening the sheet metal into various shapes and sizes. Seams and joints are sealed using specialised tapes, mastic, or mechanical fasteners to prevent air leakage.

In summary, sheet metal ductwork is a crucial component of HVAC systems, providing efficient and reliable air distribution throughout commercial and residential buildings. Its sturdy construction and careful design help maintain optimal indoor air quality and comfort. Analysing the pros and cons of different ductwork materials like sheet metal ductwork is a crucial aspect of any installation job. It minimises issues after the system has been installed and maximises efficiency throughout its lifecycle.

Fiberglass Ductwork:

Fiberglass ductwork consists of fiberglass-reinforced plastic (FRP) panels and is another commonly used material in ventilation systems. Let’s delve into its pros and cons..


Thermal Insulation: Fiberglass ducts offer excellent thermal insulation properties, minimising heat loss or gain in conditioned spaces.

Mold and Moisture Resistance: FRP panels are resistant to moisture and do not support mold growth, ensuring good indoor air quality.

Lightweight: Fiberglass ducts are lighter compared to sheet metal, making them easier to handle and install.


Fragility: Fiberglass ductwork can be more prone to damage compared to other materials, requiring careful handling during installation and maintenance.

Higher Initial Cost: The cost of fiberglass ductwork, including the specialised fabrication required, may be higher than other materials initially.

Limited Customisation: Unlike sheet metal, fiberglass ducts are often prefabricated and may have limited options for customisation.


Where is fiberglass ductwork utilised?

Fiberglass is made from layers of fiberglass insulation that are laminated together with an outer facing material. It is commonly used in domestic HVAC systems due to its insulation properties and ability to maintain consistent indoor air quality. Imagine a residential building with a forced-air HVAC system. The fiberglass ductwork is installed to distribute conditioned air throughout the house efficiently.

The main supply duct, typically a rectangular shape, is constructed using fiberglass duct board. It is lightweight and easy to handle, making it convenient for installation. The fiberglass duct board panels are cut to the required dimensions and assembled using specialised adhesives or mechanical fasteners.

Branch ducts, which supply air to individual rooms or zones, are also made from fiberglass duct board. These ducts branch off from the main supply duct and are sized appropriately to deliver the desired airflow to each area. The branch ducts are carefully sealed at the joints to prevent air leaks.

Fiberglass duct board has built-in insulation properties, eliminating the need for separate insulation materials. This insulation helps prevent heat loss or gain during air distribution, improving energy efficiency.

On the return side of the system, fiberglass ductwork is used for return air plenums and ducts. Return air plenums provide a pathway for the return air to flow back to the HVAC unit. Fiberglass duct board panels are cut and assembled to create the plenum, which is then connected to the return side of the AHU.

Fiberglass ductwork is also known for its acoustic insulation properties. The insulation material helps reduce noise transmission through the duct system, resulting in a quieter indoor environment.

It’s important to note that proper installation techniques and adherence to building codes are crucial when working with fiberglass ductwork. Following manufacturer guidelines and consulting with HVAC professionals will ensure a successful installation and optimal performance. Again, looking at the pros and cons of different ductwork materials will already point you into the correct path for your particular project and may help with any questions you may have for the HVAC professionals.


Flexible Ductwork.

Flexible ductwork is made from a combination of plastic and metal wire coils, allowing it to bend and flex easily. Consider its pros and cons..


Ease of Installation: Flexible ducts are highly flexible and can be easily routed around obstacles, reducing installation time and labour costs.

Cost-Effective: Flexible ductwork is generally more affordable compared to sheet metal or fiberglass alternatives.

Sound Attenuation: The flexibility of these ducts helps reduce the transmission of noise and vibrations through the system.



Airflow Resistance: Flexible ducts have a higher resistance to airflow compared to rigid materials, potentially reducing system efficiency.

Susceptible to Damage: Sharp bends or excessive stretching can cause damage to flexible ducts, leading to leaks or reduced airflow.

Shorter Lifespan: Compared to rigid ductwork, flexible ducts may have a shorter lifespan, requiring more frequent replacements or repairs.


Where is flexible ductwork utilised?

Flexible ductwork is commonly used in domestic settings where ease of installation and cost-effectiveness are prioritised, such as in attics or crawl spaces. Imagine a house with a central HVAC system. Flexible ductwork is used to distribute cool air from the air handler unit (AHU) to various rooms throughout the house.

The flexible ductwork starts at the AHU, where a connection is made to the supply plenum. The supply plenum is a distribution box that directs the conditioned air into the flexible ducts. Each flexible duct extends from the supply plenum and is routed through walls, ceilings, or crawlspaces to reach individual rooms.

Flexible ductwork is highly flexible and can be easily bent and maneuverer to fit around obstacles, making it suitable for installation in tight spaces or areas with irregular layouts. It is available in various diameters to accommodate different airflow requirements.

The inner core of flexible ductwork is made of a durable plastic material, such as polyethylene or PVC. This flexible inner core allows the duct to be bent and shaped without restricting the airflow. The inner core is surrounded by insulation, typically fiberglass or foam, which helps prevent heat loss or gain during air distribution.

To protect the insulation and provide durability, the outer jacket of the flexible ductwork is made of a reinforced material, such as polyester or aluminium. The jacket also acts as a vapor barrier, preventing moisture from entering the duct and potentially causing damage or reducing insulation effectiveness.

At the end of each flexible duct, a register or diffuser is installed to deliver conditioned air into the room. The register can be adjusted to control the airflow and direct it as needed.

However, it’s important to note that proper installation techniques are crucial for the optimal performance of flexible ductwork. Care should be taken to avoid sharp bends or kinks that could restrict airflow. Additionally, insulation integrity should be maintained to prevent energy loss and ensure proper thermal efficiency.

Fibreboard Ductwork.

Fibreboard ductwork, also known as fibrous duct board or fibre ducts, has its own set of pros and cons. Let’s explore them:



Thermal insulation: Fibreboard ducts have inherent insulation properties due to their fiberglass composition. They help prevent heat gain or loss during the distribution of conditioned air, improving energy efficiency in HVAC systems.

Sound absorption: Fibreboard ducts offer good acoustic properties by absorbing sound, resulting in a quieter indoor environment.

Lightweight and easy to handle: Compared to sheet metal ductwork, fibreboard ducts are lightweight and easier to handle and install. They can be easily cut, shaped, and assembled, making them suitable for various configurations.

Cost-effective: Fibreboard ductwork is generally more affordable than alternatives like sheet metal, making it a cost-effective option for HVAC installations, especially in residential settings.

Reduced air leakage: The construction of fibreboard ductwork minimizes air leakage through joints and seams, ensuring more efficient airflow and better overall system performance.



Moisture sensitivity: Fibreboard ducts are prone to moisture absorption, which can lead to reduced structural integrity, mold growth, and compromised insulation properties. Proper sealing and moisture control measures are necessary to mitigate these issues.

Limited application: Fibreboard ductwork is suitable for low to medium air pressure systems. It may not be ideal for high-pressure applications where other materials like sheet metal or rigid fiberglass may be more appropriate.

Code compliance: Building codes and regulations vary, and it’s important to ensure that fibreboard ductwork meets local standards and requirements before installation.

Durability concerns: Fibreboard ductwork may be less durable compared to materials like sheet metal. It is more susceptible to damage from impacts, moisture, and general wear and tear.

Cleaning challenges: Cleaning fibreboard ducts can be challenging due to their fibrous nature. Accumulated dirt, dust, or mold may be difficult to remove effectively, potentially affecting indoor air quality.

When considering fibreboard ductwork for an HVAC project, it’s advisable to consult with HVAC professionals or ductwork specialists who can assess your specific needs, provide recommendations, and ensure compliance with local codes and standards.

Ductwork is important.

Sheet metal offers durability and fire resistance but comes with a higher cost, while fiberglass provides excellent insulation properties but may be more fragile. On the other hand, flexible ductwork offers ease of installation and affordability but may have limitations in terms of airflow resistance and lifespan.

Evaluate your specific needs and consult with professionals to find the ideal ductwork material that suits your project best.

We hope this has given you a better understanding of the different types of ductwork material. If you want to understand how these systems work and all things ventilation, click this link to discover all!

If you’re looking for a company that offers ventilation maintenance, design and installation services across the West Midlands, London, and surrounding areas, contact Mid-Tech Services today. In the meantime, follow our journey on LinkedIn, Facebook and Instagram for more handy HVAC insights and news