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Understanding Air Duct Varieties: Materials & Designs

Barry Martin
December 11, 2023

Air ducts play an important role in maintaining and regulating air temperature and air quality at home and in commercial places.

For maximum HVAC system performance, it's necessary to understand the difference between different types of air ducts and their materials, designs and uses.

Here, we will give you an idea about the diverse world of air ducts to help you determine your ventilation needs.


1. Sheet Metal Air Ducts

rectangular Steel air duct

Sheet metal ducts are popular for their durability and longevity. It's made of galvanized steel or aluminum.

  • Sheet metal ducts are damage-resistant.
  • Provide smooth surfaces for efficient airflow.
  • Usually used in commercial buildings and industrial zones.

2. Fiberglass Air Ducts

Fiberglass ducts are lightweight. Fiberglass ducts are also known for their insulation properties. They are made from sealed fiberglass board panels.

Residential and commercial zones use fiberglass ducts, which provide insulation to prevent heat loss/gain.

3. Flexible Air Ducts

Flexible Ducts are made with a steel spring coil covered in thick plastic. This flexible duct has thermal insulation made from glass wool.

They are ideal for spaces like tight corners or odd designs as they are simple to move around objects. However, proper installation is necessary to prevent airflow limitations.

4. Fiberboard Air Ducts

Fiberboard air ducts have air insulation on their outside surface, which is made of boards of compressed resin. These ducts are low in cost and can fit into smaller places.

Because of their smooth surface, they can trap dust and enhance long-term air quality. Factors like usage and location can have an impact on how long this duct will last.

These ducts have ventilation challenges, may have a short lifespan, and are not a good choice for outdoor and wet usage.


1. Rectangular Ducts

Rectangular ducts have come up with a traditional and cost-effective solution in different HVAC systems. This design is popular in commercial buildings because of its easy manufacture and installation.

Rectangular ducts are used when space is limited. Because of its design, it provides more airflow. In HVAC systems that have low pressure, this increased airflow is an advantage.

2. Round Ducts

round air duct

One of the most common ducts is a round-shaped duct. It is mainly used in home spaces. It provides smooth airflow because of its space. One of the major advantages of a round duct is that it can be installed quickly because joining the pieces is easy.


  • Economically affordable to set up.
  • Airflow increased on the round surface.
  • Minimize sound pollution when the system is running.


Height restriction depends on their location.

3. Oval Ducts

Oval ducts are a kind of design that is similar to both round and rectangular ducts. In a state of more pressure, this duct becomes more rounded. Some advantages of oval ducts are:

  • Provide high airflow efficiency, the same as round ducts.
  • Reduce air resistance because of its smooth and curved surface.
  • Minimize turbulence noise because of its curved surface.
  • Increase overall performance and decrease air leakage caused by their seamless connection features.


1. Return Ducts

air return duct

It’s crucial to maintain balanced airflow in the HVAC system. Return ducts bring back air into the system. It is normally found in the middle spots of residences or sometimes near vents.

These ducts eliminate unconditioned and musty air from indoors. After sucking air back into the return ducts, it passes through a filter which removes dust and pollution from the air. This process makes sure that the air quality is good on the inside.

2. Supply Ducts

Transferring the fresh conditioner air back into the living place is the responsibility of the supply ducts. When the air is conditioned, this air is driven into the supply ducts. These ducts bypass homes' central ducting and then extend to certain rooms of your house.

Supply ducts are equipped with vents in each room from where the air will be provided into the room. These vents can be on the wall, ceiling, or floor. Every room has separate vents, which help to control the air temperature individually for personal comfort.

The existent air of the room is mixed with the conditioned air supplied by the supply ducts in order to create a comfortable environment. After the conditioned air fulfills its job, the air is again brought back by return ducts through the natural airflow. This process is repeated to maintain a balanced temperature.

Which Type of Air Duct is Best


Fiberglass and Fiberboard ducts are frequently used in commercial buildings as they help to lower the sound of heavy noise in commercial HVAC systems. On the other hand, most houses use sheet metal ducts along with flexible ductwork used in the corners and narrow spaces.

Sheet metal air ducts are a good choice because they need less cleaning as they have a smooth surface. Air duct installation mainly depends on the type of building and space in which you are planning to install an air duct.

You can also read another article of ours, “Choose From Multiple Types of Ductwork For Your Property,” and get more insight about choosing your preferred air duct. It will be best to consult with trusted HVAC experts in order to determine which air ducts will be a good choice for your needs.


To maintain air quality and temperature, an air duct is important for both residential and commercial places. Materials like sheet metal, fiberglass, fiberboard, and flexible have their uniqueness and advantages.

Various shapes, such as oval, rectangular, and circular ducts, are designed to fulfill specific needs. The choice of air duct mainly depends on the space where it will be installed.

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