Return Vent Filters – Everything You Need to Know

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While AC and furnace units do a decent job of filtering air impurities on their own, return vent filters can aid in this by acting as the first line of defense. Granted, regular air filters have their use but a secondary option could be the step you need to keep your HVAC system clean and efficient.

Return vent filters can help with this– the first step at straining for dust and other floating debris.

Below are details concerning return vent filters, when you should use them, and what you can expect.

How do return air vent filters work?

Return vent filters act as the first layer of protection to prevent air pollutants and other nasty particulates from getting into the air you breathe.

Installed at the return vent in your home, they pre-filter dust and other particles. This keeps your ductwork clean and extends the life of the main filter at your HVAC unit.

If you have a standard-sized return vent in your home, it will be able to accommodate a regular, rectangular-shaped air filter.

Return vent filter sizes

Return vents come in many different sizes. Depending on the size of your return vent, you may need a certain size air filter. The size of your air filter can be determined by looking at the old air filter.

If the old air filter isn’t available, then you’ll need three different measurements: length, width, and depth. They can be measured by opening the return vent and measuring the sides:

  1. Measure the short side. For example, the short side could be 15-1/2″
  2. Measure the long size. For example, the long side could be 24-1/2″
  3. Measure the depth. For example, the depth could be 7/8″
  4. Round up the measurement. The size of filter that you need to order would be 16″x25″x1″
Need a specific filter size?

Using the Filter King's filter selection tool, you can dial in exactly the size, thickness, and MERV rating you’re looking for.

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Benefits of return vent filters

There are plenty of advantages of return vent filters. Here are some of their primary benefits:

  • The first line of defense – Vent filters work as the first guard against impurities from the air being circulated inside your home. Ordinary filters certainly have their use, but some situations may call for a backup on your return vent to pre-filter the air in your home.

  • Easy to switch out – Due to its location, it’s much easier to change out return vent filters than your primary filter. Many homes have their HVAC units in the attic, so you won’t need to make as many trips up there to switch out filters.

  • Protection for ductwork – Return vent filters prevent particulates such as dust and hair from ever entering your HVAC ductwork. Notice dust building up in your ducts? The easiest way to get rid of this problem is to simply cover the return grill with a vent filter.

  • Protection for primary air filter – Using a return vent filter will extend the life of the main air filter at your HVAC unit. The filter at your return vent will pre-filter out any dust and debris. This helps prolong the life of the expensive pleated air filter at your HVAC unit.

If you have pets, incoming particles such as hair and dander might dirty up your ductwork. Using a return vent filter kit will aid in filtering out pet hair before it even makes contact with your home’s HVAC system.

What if there is already a filter at your HVAC unit?

Using a MERV-2 or MERV-3 filter in your return vent works well if you already have a pleated filter at your HVAC unit.

Fiberglass filters work well as pre-filters in return vents because they have low MERV ratings.

True Blue Air Filter

This MERV-2 air filter comes in a pack of 12 and is a great solution for return vents. It allows for a good amount of airflow and is easy to swap out.

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Why should you use an air filter with a low MERV rating? It’s all about airflow. If you use high MERV-rated filters at your return vent AND at your HVAC unit, then you run the risk of having low airflow issues.

What if there is no air filter at your HVAC unit?

If there is no air filter at your HVAC unit, then you absolutely need a return vent filter. I recommend using a MERV-5 to MERV-8 pleated air filter in your return vent. In this case, the return vent filter will be the primary air filter. So it will serve as the only line of defense against dust and particles entering your HVAC system.

Return vent filter placement

Should you use a filter in your return vent?

For most homes, return vents filters are suggested. They typically won’t cause any damage to your HVAC system and are easy to install – there’s no need for an HVAC technician.

Besides having a good primary filter, return vent filters can solve this problem immediately upon placing one on the vent. Check to ensure that your air conditioner doesn’t have issues with getting air through the vents in the first place; if so, the filter could block your airflow. Yet if your AC is in tip-top shape, it’s more than ready for a return vent filter upgrade.

Here are some reasons why vent filters are recommended:

  • Fast setup time – You can have your vent filter’s installation completed in mere minutes.

  • Immediate results – Return vent filters pose little hazard to your HVAC unit. It simply pre-cleans the air that passes in your home’s central HVAC system. You’ll see a difference in air quality immediately, especially if you use them on all of your vent grilles. Just remember to change them often (about once a month), especially if they get really dirty.

  • Works with more than air conditioners – Vent filters are great when used on some fans and even heaters, so long as the filter isn’t too close to the heat source. If you have a forced-air heater or AC with duct tubing, try placing a filter on its return vent to cut back on the dust that’s commonly spread by such systems.

When NOT to use a return vent filter

Sometimes, issues could exist with an AC system that return vent filters can’t fix. This could include openings in the ducts or tubing that’s improperly sealed. In this case, no amount of filters will fix the problem.

Furthermore, if there’s any sort of erosion to the duct interior, a vent filter won’t work since air could pass through the area with the opening. Any issues with your furnace or AC itself could prevent air from traveling past the vents properly, forcing it to work harder to heat/cool your home.

In short, ensure that your system and its vents are allowing air to flow properly before setting up a return vent filter.

Cut to fit air filters

If your return vent is an odd shape or size, then you can use cut-to-fit air filters. These types of filters usually come with velcro strips to hold them to your vent.

By using velcro strips, your filters will remain in place until you’re ready to take them down for replacement. When you change your filters, you can reuse the velcro strips for the next set of filters.

Vent Filter & Vent Register Filters Kit

These air filters cut and stick easily with included velcro. They are efficient enough to filter out common household particles, but also lightweight enough to have minimal impact on airflow. 

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How to install a return vent filter

Here’s a quick tutorial for installing a cut-to-fit filter on your return vent:

  1. Clean the vent – Turn off your HVAC unit and open the vent grille. Clean the duct and decide whether or not you want to place it inside or outside of the grille. In some cases, it might be necessary for you to keep it on the inside, more so if your filter’s tape doesn’t hold well.

  2. Cut to shape – Many return vent filter brands consist of rolls, where you must cut it to conform to the shape of your vent. Apply the tape first, ensuring that you don’t overlap the fins on the grille. To get the best cut possible, use scissors and a straight edge to measure out the shape.

  3. Press to adhere – Press the filter onto the tape you secured to the grille and hold for several seconds. If you’re using velcro, it will adhere instantly and you won’t need to hold it down.

Vent filters are sometimes poorly shaped and require that the user cut them to mimic the shape of their vent covering. Although easy to do, this can make changing them out a mild inconvenience.

Supply vent filters versus return vent filters

What are the differences between supply and return vent filters?

For starters, supply vent filters are tasked with screening out any residual contaminants from your AC/furnace. Whereas return vent filters prevent outdoor particles from entering your HVAC system in the first place.

If you are having air quality issues, then supply vent filters will just mask the problem without actually making it go away.

If there is dust blowing out of your supply vent, then there is a bigger issue with your system:

  • Your system might have an air leak, and dirty air is leaking in from your garage or attic.

  • The system might be very dirty and require a thorough cleaning.

Return vent filters do the opposite—they help filter out contaminants from ever entering your system in the first place.

A return vent filter will keep your air handler, ducts, and coils clean by filtering out particulates at the point of air intake. For some homeowners, a return vent filter could be the solution that keeps their HVAC system running cleanly and efficiently.

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