What is a Plenum in HVAC & Why Is It Important?

Every household needs an HVAC system for air conditioning throughout the year. But its efficiency depends on the ducts to give you controlled cooled or heated air in your home. The ducts are made of different materials, such as sheet metal. Others are made of heatproof solid materials like insulated plastic or fiberglass. Regardless of the material used, the plenum remains the heart of the HVAC duct.

The plenum is an essential part of the HVAC system’s ductwork. It helps to reduce humidity in the air while enhancing air circulation. A plenum’s state is crucial to ensure the efficiency and functionality of a cooling and heating system. It has to be clean to ensure smooth airflow and enable your heating, ventilation, and air conditioning system to reach desired temperatures on the thermostat.

Benefits of a Plenum in HVAC

What is a Plenum in HVAC?

A plenum or plenum box is an air distribution box in an HVAC unit. This system’s most crucial work is heating, cooling, air distribution, and airflow. It produces hot or cold air depending on what is needed to make a space comfortable. This can only happen if the air distribution box is working smoothly.

The plenum is connected directly to the supply outlet and passes through a filter that removes dust, dirt, and many other contaminants. The hot or cold air is pushed through ducts, goes through the plenum, and is distributed throughout the system. A plenum improves air quality while reducing energy costs in a home or a commercial building.

After some time, the air filters must be cleaned or replaced. They get dirty, and if not checked, the cool or warm air may be blocked from reaching the targeted space. It remains in the plenum and comes out through the vents in minimal amounts; in some cases, nothing comes out.

A plenum box is on both sides of the heat exchanger or fan. This is where the air goes first for cooling or heating before it’s sent into the AC, furnace, or heat pump. Most HVAC systems come with two plenum boxes, the return and supply plenum boxes.

Why do we Use Plenum in HVAC?

Installing an HVAC system is easy but should be done by a professional technician. Even with proper installation, a plenum should be appropriately maintained for efficiency. It is an important part of your home air distribution. If this box stops working, the cooling or heating in your house will be negatively affected. Without a functioning plenum, a house can get extremely uncomfortable. We use plenum in HVAC because it guarantees the following:

  • Efficient distribution of air in your home.
  • Elimination of different airflow problems
  • Ensures improved quality of your indoor air
  • Reduced energy costs
  • Prolongs the lifespan of the HVAC system

An HVAC system makes your home comfortable. It only takes up little space in your house, but its many benefits. Some buildings have plenty of ceiling space for easy HAVAC installation. If your house has limited space, you can look for models with reliable performance without taking up any space on the ceiling.

Types of HVAC Plenums

There are two main types of plenum boxes in HVAC systems. They include the return and the supply plenum. They are essential to each other.

Supply Plenum

The supply plenum distributes air across your house or office. As the name suggests, this plenum box warms or cools the air as required. In short, it receives warm or cool air from the unit and exchanges it with fresh air. It exhausts all the unpleasant air in a room in a controlled manner. This plenum can be placed outside or inside and located at a low point within your house. It can be made of aluminum, steel, or cast iron, depending on where it is meant to serve.

Return Plenum

The return plenum returns the filtered and conditioned air in your HVAC system. It is the second stop for the air as it returns to the unit and is usually connected to the furnace, heat pump, or HVAC’s return outlet. The air goes to the conditioning systems through the return vents; from there, it cools or heats the air for redistribution. This plenum has an air filter to prevent dirt and dust from entering the system. This guarantees you clean air and keeps the unit functioning properly.

How to Seal HVAC Plenum

If you have a leaking HVAC plenum, it is best to seal it. Small leaks can cause a blow-up in the HVAC’s set up with the most excellent air transfer. This is mostly the plenum because it consists of the cooling and heating elements and the fan. It is the plenum where a lot of pressure occurs and should therefore be the first to seal and save energy and money in the long run. Here is how to seal the HVAC plenum:

For long-lasting results, use aluminum tape to seal. Do not use ordinary duct tape because it won’t last for long due to the fluctuation of temperatures. This air conditioner is expected to get warm at times and cool down and will cause the duct tape to lose its adhesive in less than two years.

On the other hand, the aluminum tape can serve you for more than 50 years. It is heat and cold-resistant. It works perfectly for joints and smooth surfaces. It is readily available in hardware stores or online marketplaces such as Amazon. Follow these easy steps to apply the aluminum tape:

  • Wear rubber gloves
  • Clean the surface you intend to seal and dry it up
  • Keep the tape in room temperature or apply it while the HVAC is a bit warm
  • Cover all holes regardless of how tiny they appear.

How to Build a Plenum Box HVAC

A plenum box is manufactured in two designs. They are different in some ways, but the process of building them is the same. Here is how a universal plenum box is made:

  • Start with the measurements. They must be accurate and no error is allowed.
  • Trim your panels according to the measurements to ensure they fit in the HVAC system
  • Assemble the panels to create the plenum box structure.
  • Fix the panels with sheet metal screws
  • Place the top panel and secure it to ensure the plenum is completely enclosed.

How to make a customized plenum box

You can make a customized plenum box in 3 simples steps:

  • Start by attaching the three big panels; slide the panel edges into the slots.
  • Place the top panel just like you did with the other three
  • Secure the panels using sheet metal screws

Benefits of a Plenum in HVAC

Plenum in HVAC has some benefits, but we will list and explain the 3 main benefits of Plenum in HVAC:

Reduced Noise levels

A plenum reduces noise levels in your HVAC. They distribute warm or cool air evenly and silently. They are perfect for homes and commercial spaces because they do not cause any noise disturbance.

Improved Airflow

A plenum improves airflow within a home. It is a comfortable environment in your office or home by reducing humidity levels, and warming ensures you have or cooling temperature to suit your environment.

Protects Your HVAC against Dirt

A plenum protects your HVAC unit against dirt. If the ducts are already dirty clean them to prolong your system’s lifespan while keeping your home free of air impurities. This makes the plenum ideal for big homes and large offices where heavy traffic and air purification are essential.

HVAC Plenum Maintenance

Some HVAC maintenance issues can be sorted at home without the help of a professional. They include:

  • You can change your HVAC unit. It is easy; you can refer to the unit’s manual and see how to replace the filter. Choose the recommended filter by the manufacturer. The filters are readily available in local hardware stores.
  • Dusting the vents is also another simple maintenance task that you can do. You can remove the vent cover to inspect and clean as much as possible.

HVAC system filters need to be cleaned every two months. While you can do this, it is a good idea to have the ducts cleaned professionally. Look for a contractor who will maintain your HVAC unit according to ANSI and ACCA standards.

If you work closely with a HVAC company, they will inspect your unit and clean or repair it on time. However, some signs mean your HVAC needs maintenance. They include:

  • The mold growing on the HVAC system means your system should be cleaned. It may also produce a moldy smell from the airflow ducts.
  • If your doctor recommends HVAC cleaning
  • Your unit gets too hot or freezes sometimes. It is a sign of poor or restricted airflow.

HVAC Plenum Replacement

Over time, your HVAC system will wear out. The joints’ sealants deteriorate and allow some air to escape. A sealant with a leakage reduces the efficiency of the unit. One of the signs that you need to replace the plenum is increased power bills. Here is how to install a new HVAC plenum to replace the old one.

The good thing about replacing an HVAC plenum is that it usually doesn’t require to be replaced as a whole. Sheets and panels are expensive and if you have to replace the whole box, be ready to dig deep in the pocket.

Frequently Asked Questions

Is a Plenum necessary in HVAC?

A plenum is necessary for your heating, ventilation, and air conditioning unit. This box connects to the unit and has an important function: to bring in, remove and distribute air. It takes warm or cool air from the HVAC system and distributes in the building the ductwork. The used air is taken in through the return plenum and sends it to the HVAC’s core system. From there, the air is recycled and released as fresh air into your space. A plenum increases efficiency and ensures your office or home air is cleaned effortlessly.

What is the difference between a Plenum and a duct?

A plenum is a box that distributes air in commercial and residential spaces. It makes part of the ductwork but is different from the air duct. The main work of a plenum is to handle the air that enters your HVAC and circulates all over the system before removing it. On the other hand, the duct is connected to the plenum and used to distribute the air in various parts of your house. So the plenum is attached directly to your HVAC equipment supply outlet, but the duct is attached to the plenum.

How does Plenum Ventilation work?

Plenum ventilation facilitates air circulation in a building. It may be used to heat or cool air. The spaces between the dropped and raised ceiling or sometimes a raised floor area where you will find plenum ventilation. They allow easy airflow and keep your house fresh and comfortable.

Final words

A plenum is one of the things every home should have for easy living. All you have to do is ensure its properly maintained to eliminate risks that may occur if the plenum gets blocked or develops mechanical problems. The ducts should be installed by a professional. Besides that, let a qualified technician install and do routine maintenance. This will keep your building safe and save you a lot on repair or replacement costs.