Every home has a hidden network of tubes that transfers conditioned air to every inhabited area. These unsung heroes of your HVAC system are called ducts or ductwork, and here’s everything you need to know about them.
Understanding Duct Components and How They Work
Ducts are made of sheet metal or flexible pipes that snake through attics, crawlspaces, or basements to deliver conditioned air from your HVAC system to air vents. They are often insulated to prevent heat loss or gain and to help reduce noise or traveling air. These are the main components of the ductwork system.
Vibration Isolators
The duct system begins at the air handling unit. Here, the fan blowers push the conditioned air to where it’s needed in the house. These blowers generate significant vibrations that produce a lot of noise, which can cause great disturbance. To avoid this, HVAC technicians install vibration isolators between the duct system and the air handler.
Vibration isolators are made up of rubberized material that can absorb all the vibrations the air handler produces. It also cuts down on positive air pressure generated when the blowers push air into the ducts.
Take-Offs
The duct system has one main supply trunk that receives conditioned air directly from the indoor unit (the air handler). This main supply trunk incorporates smaller ones that branch out to supply air to different zones or floors of your house. Take-offs are fitted into those junctions to assist in the diversion of air into the subsidiary ducts.
Stacks, Boots, and Heads
There are supply ducts that allow air to travel through relatively thin walls from the basement to all rooms. These vertical supply ducts, called stacks, are very wide and have relatively thin rectangular or oval sections.
A stack boot is the connection between the duct branches and the thin wall-mounted supply ducts (also known as stacks). At the top of the stack, there is a stack head that connects to the air registers inside your rooms. The stack head can also reconnect to the standard ductwork to continue supplying conditioned air to other areas of the house.
Dampers
The duct system has volume, smoke, and fire dampers. Volume dampers, common in variable air volume (VAV) systems, adjust the airflow capacity to various ductwork components.
Smoke and fire dampers are installed inside the ducts that pass through a firewall or fire curtain. When these devices detect smoke or fire, they close the affected duct to contain the situation.
Plenums
These are the air distribution and collection units of your HVAC system. The return plenum carries air from the vents to the air handling unit, and the supply plenum directs air from the air handler to the various rooms inside your home that need conditioning.
How Air Travels Through Ducts
When you turn on your HVAC system to warm or cool your room, it first pulls air into the return ducts through the vent. The vent has a filter that traps and holds particles in the air, such as ducts, allergens, VOCs, and microorganisms.
The clean, unconditioned air is circulated through the ducts to the indoor unit of your HVAC system. It will be heated or cooled, depending on the season, before the blower fans push it to the main trunk, the branch ducts, and the supply ducts back into your room.
Types of Ductwork
1. Flexible Ducts
Flexible ducts are made from materials like polyethylene or PVC and are covered by insulation and a thin layer of reflective material. They are lightweight and, hence, easy to handle and maneuver, especially in tight spaces or complex areas of the house. They are also the most affordable option available.
Some disadvantages of flexible ducts include fragility and a tendency to sag. They are also less efficient in areas with extremely high temperatures and that are challenging to clean.
2. Sheet Metal Ducts
Sheet metal ducts are the common type of ductwork in most homes and businesses in the United States. They are often built out of rust-resistant galvanized steel or aluminum sheet metal.
Technicians install them by cutting and bending individual pieces of metal to create duct branches. These branches are then joined together and fully sealed at the joints to make the entire system airtight.
Sheet metal ducts are very durable, easy to clean, and typically non-porous. However, they can also leak, especially at the joints and seams.
3. Fiberglass Duct Board
This is a standard sheet metal duct lined with a fiberglass coating to enhance insulation and dampen the noise produced by the air handlers. It is popular in cold climates because it is better at preventing heat loss than the other options.
The issue that most homeowners face with this type of duct is that it tends to trap a lot of particles, including bacteria and mold, so it must be cleaned often and immediately replaced after the fiberglass begins to deteriorate.
Common Ductwork Problems
Poor Design
The goal of a ductwork system is to transfer air from one point to another as quickly and efficiently as possible. Extra twists, turns, and extensions can profoundly impact the HVAC system by interfering with airflow. Improper sizing can also affect airflow, which can cause system overheating, unbalanced air pressure, and cold or hot spots inside your house.
Inadequate Insulation
HVAC technicians must properly insulate the ductwork to prevent heat loss or gain when transporting conditioned air. The insulation, like all the other components of your HVAC system, has a finite lifespan. After around 10 years of service, they start to degrade, slowly reducing your system’s energy efficiency. If you are using fiberglass duct board, its particles may even contaminate the conditioned air, leading to respiratory and cognitive issues for your home occupants after long-term exposure.
Air Leaks
When you start noticing increased dust and allergens in the air, excessive humidity levels, and higher energy bills, you may have leaks in your ducts. Gaps allow mold, pests, and other contaminants into the ductwork and may also prevent air from making it to its intended destination.
Blockages
Damaged air filters and leaks can cause dust, pet dander, pests, and other debris to accumulate within the ducts. Over time, these particulates may obstruct airflow, making your system work harder than necessary to pull or push air. The common signs of duct blockage include cold or hot spots, excessive dust buildup on surfaces, bad odors, and high energy bills.
Maintaining Ducts
When properly installed, you can go for three years before scheduling professional duct service. However, since all parts of the HVAC system depend on each other, it’s a good idea to have a technician inspect your ducts during general routine HVAC maintenance.
Our professionals can detect leaks, clean the ducts, and enhance insulation. This will help extend the lifespan of your duct system and optimize energy consumption.
Call Cool Zone Air Conditioning & Heating for More Information
If you live in Peoria, AZ, call Cool Zone Air Conditioning & Heating today with any questions you may have about your ductwork. We install, repair, and routinely maintain ducts. Our other related services include indoor air quality solutions and HVAC installation and repair.