Understanding the Different Classes of Ductwork

Sheet metal is the most commonly used of the four duct materials, and fiberboard is composed of fiberglass yarns that have been bonded together with resin. When it comes to air conditioning systems, there are three main types of ducts: flexible, rigid, and semi-rigid. To help you make an informed decision, we have gathered information on each of these duct systems. Flexible ducts are usually round tubes formed by steel wire propellers covered in a flexible yet durable plastic. Most flexible ducts are also surrounded by insulation to maintain the desired temperature.

This type of air duct is the easiest to install and the second least expensive. Flexible ducts are the best type of duct for use in tight or awkward spaces where it would be too difficult to install rigid ducts. Because these air ducts are flexible, they can be bent around fixed structures to fit into almost any space. However, flexible ducts are prone to kinks and bends that can restrict air flow and decrease the efficiency of the air conditioning system.

The ridges inside the ducts can also reduce airflow slightly. Another advantage of flexible ducts is that they are great for air quality. Since the ducts are made of plastic instead of the fiberglass that some rigid ducts form, no hazardous particles are released into the air, meaning that fewer air pollutants need to be inhaled. This plastic is also resistant to mildew and rust, which means that air quality stays clean for much longer. Flexible ducts are less likely to leak air from the air conditioning system than rigid ducts, although they are more likely to be punctured. This type of duct is made of a metal wire coil and is covered with a layer of flexible plastic.

The flexible air duct also has thermal insulation made of glass wool, but also of other materials such as polyethylene or metallized PET. Flexible ducts usually look like a cube and have no elbows or gaps. Your home will likely have a flexible air duct if you're short on space. Rigid-type ducts can also be lined with fiberglass. This type of duct is very similar to sheet metal ducts, but they have an internal or external fiberglass coating.

These ducts are preferred in commercial buildings and offices, since air ducts lined with fiberglass have the ability to dampen the sound of the air conditioner. Oval ducts belong to this class and are perfect for narrow-walled cavities, although technically they are only flattened round ducts.