What's a Plenum?

If you've ever wondered about the inner workings of an HVAC system, you can't forget about the plenum. While you might find the name a bit unusual, this essential component actually has a big job to do when you run your furnace or air conditioner.

This May Also Interest You: HVAC Terms Every Homeowner Should Know

HVAC plenums are responsible for distributing warm or cold air throughout homes and buildings. They're pretty much hidden from plain sight, but they definitely work hard behind the scenes.

What Is a Plenum in HVAC?

A plenum is an important part of a heating and cooling system's duct and ventilation network. Shaped like a box and crafted from sheet metal, the plenum attaches to the air handler of your HVAC system. When your furnace or air conditioner is running, your HVAC system creates warm or cold air.

The temperature-controlled air moves through your AC or furnace and into the air handler. Once inside the air handler, the plenum HVAC components guide the warm or cold air through the ductwork and ventilation system and into your space. A plenum box basically serves as the centralized location where heated or cooled air begins to travel through your HVAC system.

How Does a Plenum Differ From a Duct?

Plenums attach to the air handler and distribute warm or cool air through the ductwork and vents. Ducts are the vessels the distributed air moves through before it enters homes and buildings via return vents.

Plenums are constructed from sheet metal, while ductwork is generally made of wire coils with heavy plastic coatings, galvanized steel or aluminum. While ductwork has a tube-like, cylinder shape, plenums are box-shaped. Both components are essential to the proper function of your HVAC system, but each part has its own job.

More Related Articles:

• Gimme a Tax Break: 5 Things to Know to Get the Latest HVAC Tax Credits and Rebates

• How Much Does HVAC Repair and Maintenance Cost?

• Replacing Your HVAC Filter Is a Breeze! Follow These 7 Steps ...

• Is an HVAC Tune-Up Worth the Price? (Yes, Yes It Is)

• HVAC System Stop Working? Try These Troubleshooting Tips Before You Call for Service

Where Is an HVAC Plenum Located?

Most HVAC systems utilize both supply plenum and return plenum boxes. Both are necessary to efficiently push and pull air through the HVAC system and your indoor space. The supply plenum is generally located on the supply side of your HVAC system's air handler, while the return plenum can be found on the return side of the handler.

The supply plenum box pulls in cold or warm air from your HVAC system and pushes it through the ductwork and into the desired area. The return plenum pulls in used air from your home or building's return vents and returns it to the core HVAC system. The air is then filtered and redistributed back through the ventilation system for heating or cooling.