What Is an HVAC Trunk and Branch Duct System?

The trunk and branch system is part of the HVAC duct design that will help the airflow spread evenly to different rooms within the house. The trunk acts as a large stem that sends the air through the smaller branches at the end. The heated or cooled air flows through this system and provides a more even temperature throughout the house. Below, we will talk why this HVAC duct design works so well and how it works.

The air is sent through the trunk that usually runs through the basement ceiling of the house. The trunk is large enough to carry all of the air that will be dispersed through each of the branches throughout the house. The trunk will come to an end where the air will collect and escape through the branches.

What Is It Made Of?

The trunk is made of solid metal and the branches are made of flex duct. Since the trunk will carry all of the air into the house, it should remain straight and undamaged in order to maximize its airflow capacity.

The branches are made of flex duct. They are flexible to allow for maneuvering through the house in order to allow it to get the air to reach its final destination. There should not be any holes through the trunk or branches which could compromise the airflow throughout the house.

Placement of the Branches

The branches should be around 6” to 1 foot away from the end of the trunk. This will allow a pocket of air to sit at the end of the trunk and help the air to flow into the branches more evenly. The branches should all be spaced relatively close to each other, but not too close. There should be a few inches between each branch. They can be placed on opposite sides of the trunk at equal distances.

Where Is It Used?

The trunk and branch system is a great way to distribute the air evenly throughout the house. An uneven airflow is usually due to a poor HVAC duct design. Uneven and poor airflow will result in a decrease in energy efficiency and over compensation for when the temperature is different in one room to another.

Although a trunk and branch system is not used in all cases, it is a good option to use, particularly for homes that are no more than 2 stories high. For homes that are more than 2 stories, there are other duct designs that can be used.

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