How a Ductwork System Works

Ductwork acts as a conduit to circulate heating and cooling from the HVAC unit throughout your home or business. Air, heated or cooled by the HVAC, goes through the ductwork and to the rooms. After that, it’s circulated back through the system again.

The ductwork, whether for a home or business, is comprised of steel, aluminum, polyurethane, or fiberglass panels or sheets or flexible coils that deliver air from the air handler to the registers.

How it works

The supply air, in the supply plenum, is pushed by blowers through a supply duct trunk, where it is connected to smaller branch pipes by fittings called takeoffs. If or when the air has to move in a vertical direction, stacks, which are wide, thin, vertical ductwork, can be required to move the air through walls. They are connected to the central horizontal ductwork with a stack boot. At the top, a stack head connects the stack to more horizontal ductwork, which reaches to the end of the house.

Turning vanes are used to guide air smoothly when it’s necessary to change the direction of the airflow (up to 90 degrees) unless flexible ductwork is used. If the flexible ductwork is used, it’s imperative that the duct tubing isn’t damaged, crushed, or bent at more than a 90-degree angle.

In the room

Register heads connect the ductwork to wall-mounted (or sometimes floor-mounted) air registers. Each room in the house should have at least one air register, although they often have more than one in a bigger room. Volume control dampers at the register (or even within the ducts themselves) monitor the amount of airflow.

Back it goes

An air return register sends the air through a return plenum, which takes the air from the return register back to the central air handler. In a home, this is usually where the air filter is located and is known as an air filter return. In a commercial distribution, a diffuser or grille is used as a return register.

Essential factors

Duct design determines the flow of conditioned air or heat throughout the building. The size of the HVAC unit, ductwork, and registers depend on the extent of the area to be heated and cooled. If the HVAC unit is too small for the ductwork, it will blow without creating enough pressure to deliver air to each of the registers. If it’s too large, it’s cost-prohibitive, since HVAC units vary significantly in price based on the type and the number of BTU’s they can deliver. So, the system must be designed for the space that it heats and cools.

Other factors that affect ductwork installation include the type of HVAC, the layout of the house, the number of registers, and the number of temperature-controlled zones. A poorly designed or improperly installed ductwork system can decrease the efficiency of an HVAC unit be as much as 40%.

If you have heating and cooling needs, want to know more about ductwork, or are having problems with your HVAC system, give us a call!