The most common and well-known type of duct system is sheet metal air ducts. These are made of aluminum or galvanized steel and are used in many HVAC systems. Fiber air ducts are also available, which are constructed from compressed resin plates bonded together with organic glass fibers. These ducts come with an aluminum face on the outside, which can be etched to look like other ducts or painted with several colors.
The downside is that fiber air ducts often have a shorter lifespan than other types of materials, depending on the environment and usage. Fiberglass air ducts are actually sheet metal ducts lined with a fiberglass coating inside or outside the ducts. This coating provides insulation to prevent air loss and helps to avoid condensation problems. Flexible air ducts are made of a steel wire propeller with spring, encased inside a 2-layer polymer plastic. These are some of the most modern options available, as they offer a low starting price and a light weight that makes them very easy to install.
Although flexible ducts are usually installed in a single continuous piece, a seam leak may occur when connected to rigid sheet metal ducts. Galvanized steel is a popular material for air treatment systems due to its strength, durability, corrosion-resistance, and weldability. Round ducts are recommended for maximum air carrying capacity instead of rectangular ducts, and they have lower installation costs. Rectangular ducts are more flexible when it comes to fitting in limited spaces and are resistant to corrosion caused by moisture. Aluminum ducts have low strength, high material costs, thermal expansion issues, and poor weldability. Fiberglass ducts are insulated as part of their construction and their applications include underground duct systems.
Semi-rigid ducts are the best when it comes to ventilation as they don't lose air when properly installed by technicians. Sheet metal ducts often use fiberglass insulation that has a metal sheet that acts as a vapor barrier. This coating provides insulation to prevent the formation of condensation. Each type of air duct has its own advantages, but rigid and semi-rigid ducts are usually the most durable and efficient. In terms of materials, experts agree that sheet metal ducts are superior.
Aluminum or galvanized steel ducts eliminate the risk of mold formation due to their non-porous surface and are easier to clean than other types of air ducts.
