Non-insulated flexible ducts connect to HVAC ducts and direct airflow around obstacles and corners. They are made using a thin sheet of metal folded like an accordion, allowing them to bend and flex around obstacles. Their metal construction lets them move higher-temperature air and withstand more abuse than non-insulated air connectors. Due to their increased durability and how they transfer heat to their surroundings, they are commonly used as part of a combustion system exhaust in mechanical spaces.

Non-insulated air connectors connect to HVAC ducts and direct airflow around obstacles. They are made using thin plastic films stretched over a coiled metal frame which provides minimal resistance to heat transfer to the surrounding environment. They are intended for use in low-to-medium-pressure commercial and residential HVAC systems. Due to their construction, they are not recommended for high-temperature exhaust applications.

Insulated flexible ducts provide a flexible path for treated air to be moved through while reducing heat transfer to the surrounding space. They contain an insulating layer wrapped on both sides by a moisture and abrasion barrier. While they do not need the additional labor and insulating materials required to install rigid ducts, they are generally less durable. They are best suited for supply and return lines in low-to-medium pressure heating and air conditioning installations such as residential and commercial applications.