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Types Of Home Air Ducts


Home air ducts are networks of tubes in walls, floors, and ceilings that carry air from furnaces and central AC units to distribute it as desired. They’re typically constructed out of sheet metal or fiberglass-lined.

Filters can become clogged with dust, debris, and mold – which reduces HVAC system efficiency and has negative implications on indoor air quality.

Sheet Metal

Sheet metal ducts are one of the most popular options available for home air ducting needs, typically constructed of galvanized steel for optimal corrosion protection and custom fabricated on-site to suit unique design specifications. Plus, sheet metal doesn’t rust compared to other forms of ductwork!

Galvanized sheet metal offers a smooth interior surface, which reduces resistance to airflow while also resisting damage and bacterial growth. Furthermore, this less expensive alternative to fiberglass can even be used in humid climates.


Also read: Does home warranty cover air duct cleaning?

Fiberglass ducts can be found in many homes and offices, yet their lifespan is shorter than other duct materials. Not intended for outdoor use and in humid environments can support mold growth; musty or oil-like smells could indicate rodent droppings or cockroach shells being present, as musty odors coming from inside ducts should also be addressed as these could indicate an underlying issue that may require further investigation.

Flexible Ducts

Flex ducts offer an economical and easier alternative to metal ductwork, providing less expense while being much easier to maneuver around obstacles. However, their less durable nature means installation must be undertaken carefully – their thin inner polymer tube punctures easily while their foil jacket becomes brittle over time, and cleaning becomes more challenging than metal ducts. Furthermore, it’s crucial that they have an appropriate metal takeoff installed in their attic as well as sufficient class 3 insulation in order to properly insulate them against potential risks.

Flex ducts require proper strapping and support in the attic to avoid sagging that causes static and reduces airflow, as well as difficulty inspecting them for issues, such as sharp bends that reduce airflow or kinks in insulation. In order to detect potential issues like sharp bends that restrict airflow or insulation kinks, it is also essential that any joints are sealed using UL-181-rated duct mastic, and any connecting vent or register boxes are made using metal elbows instead of plastic ones.

Stack Ducts

Idealistically, each room with supply registers should also feature a matching return duct; otherwise, pass-through grilles or other design elements should allow airflow between rooms.

Maintain a tight fit between all ducts to help ensure even temperature distribution and reduce leakage. Insulate any unconditioned areas where unconditioned spaces exist before mechanically fastening the joints together. Perform annual checks or have your connections professionally inspected if you require.


The stack effect occurs when temperature and air density variations between indoors and outdoors create buoyancy forces driving airflow. Because warmer indoor air is less dense than cold outdoor air, warmer air escapes through attic vents while cold outdoor air enters via lower openings like duct leaks or bypasses, decreasing comfort while simultaneously driving up heating costs due to forcing your system to work harder in order to keep your home at an acceptable temperature. This forces it harder than necessary, just keeping you at an acceptable temperature!