Return Air Vents – Here’s What You Need to Know

Your home’s HVAC system is responsible for keeping a comfortable climate in your home. This is done by sucking in air from the inside of your home, filtering and cooling/heating it, and then blowing it back into your home.

But where does your HVAC system suck in air from your home? And how does the air intake location affect the climate in your home?

In this article, I’ll go over return air vents and their location. I’ll also discuss whether you should block a return air vent and the difference between an air vent register and grille.

Location of air return vents

Most older homes (pre-1990) have one big air return vent located centrally somewhere in the home. Usually it’s located in a hallway, but could be somewhere else such as in the living room.

Newer homes usually have several small air return vents located around the home—such as the bedrooms, bathrooms, kitchen, etc.

Generally, the specific location of return air vents is due to cost rather than energy efficiency.

For instance, a home might have its return air vents in the ceiling because the ductwork runs in the attic of the home. So putting the return vent in the ceiling makes the most sense since it will have a direct path to the return duct in the attic.

How to identify an air return vent

So you’ve found an air vent, but how do you confirm whether its a return vent or a supply vent?

One way is to hold a piece of toilet paper up to the vent. If the paper gets sucked toward the vent, then its a return vent.

Another way to tell is by inspection. Return vents usually have grilles on them. This is different than supply vents—they usually have registers on them.

I’ll explain the differences between registers and grilles below.

Air vent registers versus grilles

When it comes to air vent registers and air vent grilles, you might have heard these two terms used interchangeably. While they are similar, they are actually two different things:

  • An air vent register is used on the supply vent. The register has slotted louvers inside of it that are used to direct airflow inside of a room. In most registers, the direction of the vanes are adjusted by a lever or slider.

  • An air vent grille is used on the return vent. The grille has slotted vanes that are non-adjustable in a fixed position. Its purpose is mostly for keeping objects out of the air intake.
Air vent register versus grille

Another type of air vent device is the air vent diffuser. Diffusers are similar to air vent registers, but they are non-adjustable.

While registers allow you to direct airflow in a certain direction, diffusers disperse air in all directions. 

Should you block a return air vent?

You should never block a return air vent. Blocking a return air vent will cause issues with air temperature, pressure, and circulation.

Even if a return vent isn’t completely blocked, you still need to keep it clear.

Keep all objects such as furniture, curtains, and appliances at least 1 foot away from return air vents.

Blocking a return vent can cause damage to your HVAC system by causing air leaks. Air leaks occur when there is a high pressure difference between the inside and outside of your ductwork.

If the return air vents are blocked, then the blockage will cause excess negative pressure inside your ducts. The excess negative pressure has the potential to cause your ductwork to implode on itself.

Besides your ductwork, your HVAC unit itself is at risk from the lack of airflow.

An air conditioner that doesn’t have enough return airflow can be damaged by the pressure imbalances in the system. In a worst-case scenario, wet compression can take place and cause your compressor’s head bolts to strip.

A furnace that doesn’t have enough airflow can suffer a range of issues, such as tripping out on high limit or a cracked heat exchanger.

Should you close off a return air vent?

Some people think that it’s appropriate to close one or more of their return vents depending on the season, such as in summer or winter.

The truth is that you should never close a return vent—even when the seasons change.

Too much return air is never a bad thing. So there’s no reason to choke or dampen a return vent.

Do you need a return air vent filter?

Most homes have either one of these types of setups:

  • Air filter installed in the return duct at the HVAC unit, OR
  • Air filter installed in the return vent in the home

In most cases, either one of these filter setups are sufficient to keep your home’s air clean and your HVAC unit effective.

But what if you install an air filter in both the return duct AND in the return vent? In most cases, that’s not necessary. However, if you have tons of debris, dust, or pet hair in your home, installing both filters can help your primary filter last longer.

I talk more about this in-depth in the article below.

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