What Are the Different Ductwork Types?

Choosing the right HVAC ductwork is as important as choosing the right HVAC unit. Making sure you have durable and well-installed ductwork designed for the specific type of space you are heating and cooling is incredibly important. Like veins in your body, if the ductwork is clogged or leaking, the energy efficiency in your space will suffer.

The main job of ductwork is to direct air coming out of your HVAC unit and distribute it to different areas of your home or building. Fundamentally, every room would be a different temperature if there were no ducts. Choosing the right ductwork corresponds to the overall design of a space, the needs for budget, heat retention or noise reduction.

What types of duct work exist?

There are primarily four different types of ductwork that can be installed in a residential or commercial space. Each has its advantages and disadvantages, so it’s important to learn about each type before choosing one for your project.

Sheet metal

Rigid sheet metal is one of the most common types of ductwork you will see in North America. Made of galvanized steel or aluminum, the effect is a solid product for durable duct work. The interior traps dust and other particles, yet since it is a smooth surface it is also easy to clean. If you choose sheet metal for your space, it’s a good idea to get the ducts professional cleaned periodically to maintain good indoor air quality.

Fiberboard

Fiberboard ducts are constructed of fiberglass strands held together by resin with added foil on the exterior for added insulation. Fiberboard strands help texture the interior. Dust and debris may get trapped in these folds – so long-term air quality and efficiency may be concerning. Typically, fiberboard ducts cost less than sheet metal. A good solution to help relieve these concerns is to have a good quality air filter installed and changed out regularly. HVAC system manufacturers often provide a recommendation on which type of filter to use and how often to change it.

Fiberglass

Similar construction as a sheet metal duct, fiberglass ducts have an additional fiberglass lining to help limit heat loss. Because of the sealed interior lining, these ducts require extreme cleaning that may cause ductwork to be less durable. Containing fiberglass lining can be plus to this type of duct to help reduce the noise an HVAC system may make; thus it is a favored choice in commercial buildings.

Flexible ducts

Unlike other types of duct work, these ducts are not rigid. Have a tight space requiring extra flexibility? Then this type of duct is a great choice as it is constructed of a steel spring coil covered in thick plastic. Flexible ducts are easier to install and less expensive than rigid ducts. Yet, good installation is key to avoid punctures, kinks, or sags to avoid hurting the HVAC system’s overall performance.

Follow the code and use the proper guidance tools

Using the right guidance tools to correctly design duct system should start with the use of Manual D. This manual from the Air Conditioning Contractors of America is the tool contractors are taught to use to calculate correct ductwork sizing for a space and HVAC system. The intent is to distribute air evenly, as to balance indoor temperatures and humidity.

If contractors design a ductwork system incorrectly, the space will have hot/cold rooms because not enough or too much conditioned air is getting to them. Large amounts of energy and money may be wasted as energy bills will reflect higher than what they should be.

Quality ductwork design and material choices

To minimize heat loss from heated air and the heating of air-conditioned air, the best ductwork design will deliver conditioned air using the shortest routes possible. Designing the placement of an HVAC indoor unit to a centrally located position will prove to be the most efficient and compact route to deliver air.

In many regions, building codes specify for R6 or R8 insulation for ducts located in attics. These recommendations change periodically, so it’s best to understand your local or regional requirements. Some installers install an increased rated flex type ductwork such as R12 to R16. The cost may be minimal, and your customer may recoup it in the first two years of installation through lower energy costs. 

Avoid potential problems

Problems with ductwork occur with improperly installed and incorrectly sized ductwork. This results in rooms that are hotter or colder than others creating poor airflow. Ducts that are too small may be noisy or increase the amount of dust and other allergens throughout a space. Pressure that is too high may cause duct damage, producing leaks that eventually mean wasted energy and money. These may also not have sufficient pressure to move conditioned air to rooms or zones that are further from the blower. Moisture condensation from having too-small ducts can lead to mold.

Your HVAC system will have to work harder and may have mechanical problems compromising the life of the unit. Dehumidification of air is also a big concern as faulty ductwork design could lead to airflow restrictions or temperature imbalances.

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