What Is a Return Air Vent and What Does It Do?

It’s easy to understand what a return air vent is, and it’s important to know about its role in your HVAC system. Return air vents draw in air and return it to your home’s heating and cooling system. They’re a vital part of your home’s ductwork, keeping your home comfortable and evenly pressurized. Learn how these vents work, what you need to watch out for, and what to do if you notice a problem.

What Is a Return Air Vent?

Think of your home’s central heating or cooling system as a closed loop. The air handler holds the furnace, which heats the air. The blower pushes this warmed air toward the living areas. The supply vents release the warmed air into the rooms of your home, and the return vents suck it back in, sending it back to the air handler to start the process all over again. The same applies to central cooling. Without a return vent, the loop can’t close.

Return Vents vs. Supply Vents

The difference between return vents and supply vents is the direction of airflow. In fact, this is how you tell the difference between a supply vent and a return vent: Hold your hand or a piece of paper in front of the vent. If you see or feel air blowing out, that’s a supply vent. If you feel suction, that’s a return vent.

The Purpose of Return Air Vents

Without return air vents, what would happen to the air in your home? That warmed or cooled air, sent to each room in your home, would stay put, and more air would be added each time you turned the HVAC system on. Air pressure would eventually build and build without a vent to release it. Return air vents let the air circulate and keep the pressure stable. But they have other important jobs, too: 

• Maintain temperature: Return air vents draw air back to the furnace or evaporator so that it can be heated or cooled as necessary.

• Maintain pressure: Without a return air vent, you wouldn’t be able to maintain neutral air pressure.

• Maintain cleanliness: Return air vents bring the recycled air through an air filter before it’s released into the home again, keeping dust and dander out of the air for cleaner, fresher air in your home.

• Maintain efficiency: Properly operating return air vents keeps your heating and cooling system working efficiently, which helps lower your utility costs.

Locating Return Air Vents

The location of your return air vents often depends on the age of your home. For older homes, there might be just one cold air return located near the center of the home; newer homes usually have multiple air return vents, sometimes one in each room. Either way, the best spot for an air return vent is on an interior wall, away from the supply register. They can be placed near the floor or up near the ceiling; lower is better for returning cold air since it sinks, and higher is better for warm air since it rises.

Return air vents are often pretty large, or at least larger than the supply vents; you can explore creative ways to hide ductwork if you find the standard-issue metal grille unattractive.

Opening and Closing Return Air Vents

No matter where your return air vent is located, make sure it isn’t blocked. You may have heard that it’s smart to close vents in unused rooms, but it can actually affect the performance of your HVAC system—and not in a good way! There are several reasons you really don’t want to close off your return vents.

First of all, consider what happens if you block the return air vents: You prevent the air from, you know, returning. That will force your HVAC system to draw new air from wherever it can find it, including the dirty, dusty outdoor air, which might be drastically warmer or cooler than the temperature you’d like to keep your home. 

Secondly, reduced airflow can lead to a number of problems with your system, including:

• Excess wear and tear on your system’s parts

• Increased pressure on your air ducts

• Moisture, mold, and mildew that can reduce air quality and affect your health

• Carbon monoxide leaks that can be dangerous and even fatal

Instead of trying to close off your forced air return, make sure the vent is clean, clear, and unobstructed. Move furniture or decor away from the vent, too. With the average cost of air duct cleaning sitting at about 25 cents per square foot, it could be pretty smart to have your ductwork professionally cleaned while you’re at it.

What Happens If You Don’t Have a Return Air Vent?

If you’re missing a return air vent or you don’t have enough return air vents for your heating system or square footage, you’ll probably notice it. There might be wide differences in temperature in different parts of your home or noticeable changes in airflow. Your HVAC system might break down more than it should, and you may even notice condensation or damage on your air ducts. (If that’s the case, make sure you know how to stop condensation on air vents so you avoid moisture problems.)

To fix the reduced airflow, you have a few options. You can try to add jump ducts or jumper vents to your existing system. These are short, flexible ducts that can improve airflow, especially in bedrooms where doors are often closed. Or, you could “undercut” the bedroom doors, which allows air to flow back to the home’s main air return vent. Finally, you could install direct returns, which would tap into your existing ductwork.