What Are the Types of Duct Systems

What Are the Types of Duct Systems?

Flexible ductwork, rigid ductwork, and semi-rigid ductwork are the primary types among duct systems. From newly constructed commercial buildings to long-lived apartments, the extensive network of ducts ensures healthy air contributions overall. To acknowledge the reason for keeping the ducts in top condition, you need to know about different duct systems.  

From Basics- What Are the Types of Duct System

The HVAC system that stands for heating, ventilation, and air conditioning of a commercial building consists of some tube-shaped bendable coil known as ducts. They are typically made of a wire coil covered with durable plastic and enclosed by insulation.

The distribution of hot and cold air in different areas of the building is regulated by these ducts. You can contact duct technicians to keep it up-to-date. However, you should also be aware of duct systems so that you can choose to install the right one for you. The inconsistent temperature or ineffective air conditioning are some common issues with air ducts.

Owning an apartment or business comes with tons of responsibilities. If you face issues with your duct system, the recovery is quite a frustrating job. So the best thing to do is provide enough attention to a duct system which it often fails to get.

Different Sorts of Ductwork

The type of ductwork one should use relies on his HVAC needs. It can be figured out by an HVAC professional. However, there are mainly three types of ductworks. They are flexible ductwork, rigid ductwork, and semi-rigid ductwork. 

Flexible Ductwork

Flexible ductworks are the easiest to install and available at a very reasonable price. It is the second least costly among the three duct systems. These ducts are round tubes usually made up of steel wire helixes coated in flexible yet durable plastic. Most of them are also covered by insulation to keep the air at the proper temperature. 

These ductworks are best to use in compact or awkward spaces where rigid ductworks would be hard to install. The main reason behind this is these ductworks are flexible enough to bend around tight structures to work in almost any area. flexible ducts are liable to bends and kinks that can inhibit airflow and decrease the efficiency of the HVAC system. 

The ridges on the inside of the ducts somewhat help to reduce the airflow. It is also excellent for air quality. As the ducts are made of plastic, not fiberglass, it reduces air pollutants. 

Plastic is also resistant to rust and mold, which keeps the air quality clean for a long time. They also have less possibility to leak air from the HVAC system. However, it is more prone to being deflated.

Rigid Ductwork

Rigid ductworks are available in various sizes, shapes, and materials. They can be either cylindrical or rectangular. As per their name, they are rigid enough and are not capable of bending which reduces the risks of bends and kinks limiting airflow. Unlike flexible ducts, they can’t be deflated or torn.

However, the disadvantage is you can’t use this ductwork in tough spaces as they aren’t flexible enough. The three primary types of rigid ductwork are sheet metal ducts, fiberglass lined ducts, and fiberboard ducts.

Sheet Metal Ducts

Sheet metal ducts are generally made of aluminum or galvanized steel. Aluminum ducts are lightweight and easier to install. These ducts are also mold-resistant like flexible ducts due to their nonporous material. As a result, they also offer a better quality of air. 

They are also durable as due to metallic structure they can strictly hold their shapes. The disadvantage is they are more likely to leak where two coils get together. 

Fiberglass Lined Ducts

They can be said to be a kind of sheet metal duct. The difference is they are lined with fiberglass on either the outside or inside of the duct tube. This lining delivers insulation that maintains the correct air temperature, prevents the formation of condensation, and muffles the sound of the system. 

This ability to muzzle sounds makes this ductwork ideal for offices and commercial buildings. The major drawback of fiberglass-lined ducts is that the lining degrades over time and exposes fiber to the air. It pollutes the air and the exposed fiberglass particles can lead to major health problems. 

Also, they are hard to clean as they can harm the lining and cause more exposure to fiberglass particles. It includes a porous surface which makes it prone to mildew, bacteria, and mold. Thus these ducts are needed to be cleaned by HVAC professionals.

Fiberboard Ducts

Fiberboard is a kind of fiberglass duct as the difference is in these ducts, the fiberglass is sealed to prevent the exposure of the particles. The outer part of the boards is covered by a foil which works as a blockade of air and moisture. These ducts themselves are amazing insulators. 

Fiberboard ducts are the least expensive of all types. However, like fiberglass-lined ducts, these ducts are also likely to mold and rust. Besides, the inside of these ducts is harsh. It results in friction in the airflow and decreases the efficiency of the system.

Semi-rigid Ductwork

Semi-rigid ductworks offer a zero-leakage ventilation system. Also, they have great crushability levels. Moreover, some semi-rigid ducting systems provide versatility by switching between oval and round ducting without losing any system performance or hydraulic pressure loss. They are non-prone to any kind of mold or bacteria.

Effective Ductwork

Effective ductwork makes sure that your comfort isn’t compromised. It should deliver an accurate amount of heated or cold air regardless of the needed amount of air. It should consist of a proper seal to preserve the airflow. They should be perfectly sized.   

The supply and return of airflow should be well balanced. It curtails air temperature gains and losses. Thus it’s difficult to keep temperature disparity between the air handlers. Too high or too low-temperature deviation will lessen air duct proficiency and raise your energy bills.

Flexible Ductwork


What is the main duct?

Duct pipes and trunks are the elementary channels that provide a path for cooled or heated air to blow throughout your house. The duct trunk is known as the main duct from the boiler. It is generally made of steel. 

What is the lifespan of a duct system?

Ductworks mostly last between 10 and 15 years in most houses. It is recommended to change the ducts if they are older than 15 years to prevent leaks, gaps, drafts, and pests.

Why flex duct is bad?

Flex duct is bad as it has certain disadvantages that make it a less popular choice in some cases. These include the lack of structural integrity, the need to constantly be maintained, and above all, not having those qualities necessary for long-term durability.


Duct systems are somewhat underrated lookouts among house concerns. It is really important to select the right duct system and maintain it properly as this function directly affects the central unit’s performance. The perfect ductwork according to your HVAC system can make your home environment relaxing than ever.  

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