Types of Air Duct Systems

Air ducts are an essential part of any commercial building, and there are a few different types of air duct systems that you may come across. The materials used and the shape of the ductwork are usually determined by the requirements of the business and the layout of the property. Air ducts can be utilised in numerous ways, and many have a specific use or environment to which they are most suited.

Industrial duct cleaning

Types of Air Duct Systems

While all air ducts function similarly to distribute air throughout a building, they can be differentiated by various means, such as the airtightness of their construction, how well air flows through them and their shape. Some air duct types deliver air from outside the property, and some distribute air within a building. There are many different ways these air duct systems operate and how they collect or filter their air supply.


Sheet Metal Air Ducts

Sheet metal air ducts are the most common type of air duct. They are made from galvanised steel or aluminium and are often used in commercial and industrial settings. Sheet metal air ducts are durable and can withstand high temperatures, making them a good choice for applications where air needs to be heated or cooled.

They may be round, rectangular and sometimes spiral oval in shape too. Sheet metal ducts have a non-porous surface making it less likely for mould or mildew to grow.


Fibreglass Lined Air Ducts

Fibreglass lined air ducts are made from sheet metal lined with fibreglass insulation, either internally or externally. This type of air duct is used in areas where noise from the HVAC unit is a concern, as the fibreglass lining helps to reduce noise levels. Fibreglass lined air ducts are also moisture resistant, making them a good choice for applications where there is a risk of condensation. They are also excellent for insulating ductwork from heat loss and reducing energy costs.


Fibreboard Air Ducts

Fibreboard air ducts are made from compressed resin bonded glass fibres. The interior surfaces are sealed off by tightly woven fabric that prevents any unwanted fibre particles from entering the ductwork. In addition, Fibreboard air ducts have a foil surface on the outside that serves as an effective barrier and water-repellant while also providing sound absorption qualities which make them perfect for businesses with noisy exhaust systems or HVAC units running throughout the day.

Fibreboard air ducts are light, flexible and easy to install but are not as durable as other types of air ducts. They are available in round and rectangular shapes.


Flexible Air Ducts

Flexible air ducts are constructed with a spring steel wire helix inner, wrapped in an insulating layer of polymer plastic. These lightweight and inexpensive ducts can be easily installed. In addition, the short lengths of these flexible pipes provide better performance when compared to longer ones because it takes less time for airflow through them, which keeps energy costs down.


Air Duct Materials


Galvanised Steel

With its ability to expand and contract, galvanised steel is the most common material used in ductwork fabrication. Ducts warmed by heating systems will see their size increase while cool air flows through these same channels at lower temperatures, causing them to shrink back down again.



Aluminium is a common metal used in air ducts because it is lightweight yet strong. As aluminium does not rust, it protects against the problems that may occur over time with other air duct materials. They may be round, rectangular and sometimes spiral oval in shape.

Aluminium air ducts have a non-porous surface making it less likely for mould or mildew to grow. Additionally, aluminium dissipates heat quickly, making it a good choice for air ducts in hot environments. Its durability ensures that your system will last longer than expected while providing high-performance levels when needed most.


Stainless Steel

Stainless steel is a popular material for air ducts and extraction systems used in commercial kitchens. Some exposed varieties will be found outside, while others can stay hidden away from view.

Stainless steel air ducts are resistant to rust and corrosion, making them a good choice for applications where moisture is present. They are also easy to clean and maintain, making them a popular choice for schools, hospitals, and other commercial buildings.


Carbon Steel

Carbon steel is a type of steel that contains carbon. This metal alloy, made up of iron and carbon, is another material used in air duct construction. Carbon steel is strong and durable, making it a popular choice. It is an excellent material for applications that involve flue pipes and chimneys because it can withstand high temperatures.


Non-Metallic Ducts

Not all air ducts are made from metal; non-metallic air ducts are made from various materials, including fibreglass, plastic and fabric.

For chemical exhaust and underground duct systems, fibreglass-reinforced plastic (FRP) is a popular material.

Fabric ducting is commonly found in laboratories, school cafeterias, and large office buildings.

Some ducts are made of a softer, flexible material. Flexible ductwork has an inner liner supported by coiled wires and covered in insulation, making it perfect for airflow applications.

These ducts are all flexible and lightweight, making them easy to install. In addition, non-metallic air ducts are available in various shapes and sizes, making them a versatile choice for your air duct needs.


Air Duct Shapes


Round air ducts are the most common type of ducting. They are made from a round metal pipe and are sometimes covered in fibreglass insulation. Round air ducts are easy to install and are less likely to accumulate dust and dirt than other types of air ducts. 

When it comes to airflow, round ducts are the clear winner. They can be installed in any orientation and produce as much airflow with less metal than their square counterparts!


Rectangular and square air ducts are used in commercial buildings to transfer air between rooms fitted with air handling units. They can be made of aluminium sheet metal and use fibreglass insulation to prevent air and heat leaks. Rectangular ducts can fit into walls or above ceilings.


Oval air ducts are less common than round or rectangular air ducts, but they have some advantages that make them worth considering. Oval ducts are a popular choice for their low height requirements.

Oval air ducts create less obstruction than round ductwork, so they’re better if you need to pass through tight spaces or around things like machinery with limited space. They are also perfect for buildings with unusual layouts or difficult-to-fit spaces.


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Commercial air ducts come in various shapes, sizes, and materials, each with advantages and disadvantages. While we don’t offer air duct installation, the type of air duct you choose will directly affect the type and frequency of duct cleaning required to ensure it is maintained to industry standards.

Whatever air duct type you have, Deduct Ltd. has the knowledge and expertise to meet your commercial air duct cleaning requirements! If you would like more information on how we can help, please contact us.