4 Rules for flexible ducts that remodelers need to know.

When remodeling a home, one of the most critical components of the HVAC system is the ductwork. Flexible ducts are a popular choice due to their ease of installation and flexibility. Standard HVAC systems and some venting applications employ Flexi Duct R6, with its R6 insulation giving 33% more insulation than the typical R4.2 product. More thermal efficiency is provided by the extra insulation, thus reducing energy consumption, and making it more popular. However, there are specific rules that remodelers need to follow when working with flexible ducts to ensure optimal performance and safety.

  1. Use the correct size

Flexible ducts come in different sizes, and it is crucial to use the correct size for the airflow rate required by the HVAC system. Using the wrong size can lead to reduced airflow and inefficient heating and cooling, resulting in higher energy bills and an uncomfortable indoor environment. To ensure that the right size is used, remodelers should consult the manufacturer’s specifications or work with an HVAC professional.

  1. Install properly.

Correct installation is necessary to avoid kinks, drooping, or twisting in flexible ducts, which can reduce airflow and raise the risk of fire. Following the manufacturer’s instructions and making sure the ducts are not bent or squeezed past the advised limits are crucial for a proper installation of flexible ducts. The ducts must also be stabilized with straps or hangers at regular intervals to prevent sagging or kinking.

  1. Avoid sharp bends.

One of the most common mistakes made when installing flexible ducts is making sharp bends. Sadly, inadequate framing planning and poor subtrade coordination led to a variety of bends and kinks on numerous job sites, some of which all but totally obstruct airflow. When the drywall crew starts their job, thoroughly inspect the flexible ductwork since after it is up, it is impossible to find these issues. Kinks are relatively simple to identify, but a severe bend is more difficult to perceive and can restrict airflow and reduce efficiency. Remodelers should avoid sharp bends and use gradual curves to ensure optimal airflow. Additionally, it is crucial to ensure that the flexible ducts are not stretched too tightly, as this can cause them to deform and restrict airflow.

  1. Seal properly with mastic

Flexible ducts must be sealed correctly to prevent air leakage, which can lead to energy loss and decreased efficiency. To seal flexible ducts properly, it is essential to use high-quality mastic, which can withstand temperature changes and airflow in the ductwork. Duct mastic that has the UL-181 rating should be used to seal any duct, flexible or rigid. There are many purposes for duct tape, but closing ducts is not one of them. Remodelers should also ensure that the connections between the ducts and the HVAC system are tight and sealed to prevent air leaks.


For remodelers who need to transfer air through confined spaces or around obstructions, flexible ducts are a flexible and reasonably priced choice. Remodelers can make sure that their flexible ducts continue to work at their best and use energy efficiently for many years by adhering to these guidelines.


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