Do I Need Filters in My Return Vents?

The chances are high that your house has quite a few return vents. Should you install a filter in every single one of them?

In general, it is recommended to have an air filter in every return vent (as long as you choose the one of the right size and thickness). The filters will improve the air quality in your house and will protect the HVAC equipment from dust, pollen, pet dander, and hair.

What Does a Return Air Vent Do?

Return vents are the ones that suck in the air from the house and send it to the heating and cooling unit.

These air vents have a few important functions:

  • Return air vents help maintain air pressure

As the heated or cooled air gets delivered into the room, the ‘old’ air needs to escape somewhere. Return vents pull this excess air back into the HVAC system, and this helps maintain the right pressure in your house.

  • They help improve air quality

When the air gets pulled into the system, it passes through a filter that captures a lot of airborne particles.

Read: Ceiling Vents Vs. Floor Vents. What’s The Difference And Efficiency?

Where Is the Return Air Filter?

Usually, you’ll find the air filter in the return air duct. Look for a large metal grate on your ceiling, wall, or floor.

In general, return air ducts are installed under stairwells, in hallways, or in any big open area in your house.

Remember that there is supply and return vents. The latter are almost always bigger and they don’t have louvers.

If you are questioning whether or not it’s a return vent in front of you, simply turn on the unit’s fan and hold a tissue next to the return vent. If the tissue gets pulled toward the vent, then it’s the return air.

Read: How Strong Should Air Come Out Of Vents?

Should Every Room Have a Return Vent?

Older systems had one or two return vents that were strategically placed in the house. However, nowadays, experts recommend installing a return vent practically in every room, if you want your heating and cooling system to be as efficient as it can possibly be.

The more return vents your house has, the better the airflow. Having multiple entry points for the air is also the most efficient way to heat or cool your house as these air vents reduce the stress that is put on the HVAC system

You can invite an engineer to calculate how many vents your house will need. The expert is going to consider how much airflow your HVAC system needs to operate at 100% capacity.

Or you can simply choose to install a return vent in every room that is larger than 100 square feet (you will need two vents for rooms that are larger than 500 square feet).

Read: Why There Is A Bad Smell Coming From One Vent In House?

Should I Put a Filter in My Return Vent?

Do I need filters in my return vents? It is generally recommended to have a filter in every return duct. Filters protect the HVAC equipment and capture plenty of particles that would otherwise end up in the air that you breathe.

However, you should always consult an HVAC expert or the manual that came with your heating and cooling system to get the right type of filters.

Filters that are too thick or too fine might restrict the airflow which, in its turn, will cause the system to overwork.

Also, do bear in mind that installing a filter would be pointless, if your ductwork is not properly sealed or if the system has cracks and holes. 

In such a case, ‘dirty’ air would be able to get into the system past the filter and no filter-related benefits would be achieved. 

Read: Do Vent Deflectors Really Work?

How to Install Return Air Vent Filter?

If your return air vent has a filter slot, installing a new filter would be easy – simply slide the new component in the slot.

The thing that you would have to pay attention to is the arrow. It should face the unit (away from the return vent).

Installing a cut-to-fit filter might be a bit trickier.

  1. Turn off the unit, open the vent grille, and clean the duct.
  2. Measure the vent and cut the filter according to the shape.
  3. Secure tape to the grille and press the filter onto that tape. You might have to hold it for a few seconds, to ensure that the filter is stuck in place.

Return Vent Filter Sizes

The filter won’t be able to do its job if the sizing is not correct. A filter that is too big might restrict the airflow, while a small filter will let plenty of air go through it unfiltered.

Bear in mind that the air filtration industry creates filters that measure a bit smaller than their slot (to make sure that they don’t get bent).

That’s why when shopping for an air filter, you might notice two different sizes – nominal and actual.

The nominal size is the rounded-up number of the actual size.

The actual size is, in most cases, about 0.25’’-0.5’’ smaller than the nominal size. If you use a ruler to measure the size of your filter, this is the size that you’ll find.

How to find your air filter size?

  • Check the label on the filter’s frame (the nominal size will be printed along the edge)
  • Use a ruler to measure the filter’s length, width, and thickness (depth). Round up the dimensions to find out the nominal size.
  • You can also measure the width, length, and depth of the intake’s inside edge. Remember that your filter should be around 0.25’’-0.5’’ smaller than the slot.

Read: Does A Basement Need Ventilation?

Best Air Vent Filters

Here are the main things that you should take into consideration when shopping for a new air filter.

  • The type of the filter

A fiberglass filter is the cheapest option, pleated filters are a bit better at trapping airborne particles, while HEPA filters are able to filter out 99.97% of all particles.

You might want to go for a HEPA filter if someone in the household suffers from allergies. In all the other cases, as long as you don’t forget to change the filter regularly, any option would do.

  • The MERV rating

Experts recommend using filters with a MERV rating between 10 and 13. Even though there are filters that come with a rating as high as 20, these ones might restrict the airflow.

  • The size of the filter

It is extremely important to find a filter of the right size. Take a minute to manually measure the size, if you can’t find the numbers on the edge of the old filter.

The most common sizes are 16’’x20’’, 16’’x25’’, and 20’’x25’’.

  • A disposable or a reusable option

Even though reusable (washable) filters are more sustainable, they, typically, don’t come in high enough MERV ratings. 

Why Are My Return Vents So Dusty?

There are two main causes that can make your return vents extra dirty – a clogged filter and leaky ducts.

In general, it is recommended to replace your air filter every 90 days. If you tend to use your HVAC system all the time, have a lot of family members, a few pets, and if you have any respiratory issues, then you would have to change the filter more often. Leaky ducts allow unfiltered air to get into your HVAC system. You should regularly check the ductwork for any holes and gaps.