Should You Put Filters In Your Return Vents? (Find Out Now!)

Matthew Mountain
by Matthew Mountain

Every home should have good air quality and airflow, and air filters ensure that air can flow freely but without the particles that bother humans and break down HVAC hardware. Air filters are found on air conditioning units and heating units alike, and getting an air filter for a heat pump is something a homeowner can do to ensure better air quality at home.

But can you put filters on return vents? Such is the question this article will answer. There’s also plenty of other useful information, so read on!

Yes, filters can be installed on return vents, but this is not a universally accepted practice. On paper, using a return vent filter makes sense, but in reality a filter may do more harm than good. If a home has generally low air quality, then it’s best to install a return vent filter.

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Protecting a Heat Pump With Filters

While it’s possible to run a heat pump without a filter, doing this is not recommended, as running a heat pump without a filter means that the heat pump will be exposed to dust, dirt, and other debris that can collect on the system’s evaporator coil. Also, a heat pump produces condensation during operation, and this can affect the system’s evaporator coil as well.

Normally, condensation is supposed to drain away from the heat pump. But if the coils are dirty, then the condensation can get trapped, resulting in a clog.

A clog in the discharge pipe will mean that condensation can’t get out of the system properly, and at some point your machine will stop working because of this. Or worse, you could experience greater home damage because of a heat pump malfunction.

Which Vents Are the Return Vents and Where Are They?

Generally speaking, a return vent is located near the home’s thermostat, and most HVAC technicians recommend that the thermostat be in the middle of the home, as this way the device can ensure that the home has heat evenly distributed throughout. A return vent can be located in the wall, ceiling, or floor, and floor vents are particularly common in older homes.

Return vents do resemble supply vents as far as shape is concerned, but return vents tend to be larger. There’s usually one return vent per thermostat, but some systems utilize two thermostats—and therefore two return vents.

Multi-Zone Thermostats

Multi-zone systems, for example, have heat pumps that are controlled by two thermostats. Specifically, the thermostats control the damper doors that are inside the ductwork, and these are opened and closed (depending on what’s needed at the time). And as was mentioned above, because these systems require two thermostats, they require two return vents as well.

Distinguishing the Return Vent From the Supply Vent

Don’t know which vent is your return vent? There’s something easy you can do to distinguish the two; professionals call it the “Tissue Test”. Turn the heat pump on and then place a piece of tissue next to the vent. If the tissue blows away, then you’ll know you’re at the supply vent. But if the tissue is drawn inward, then you know you’re dealing with the return vent.

Why Return Vents Are Installed Near Thermostats

It’s common for return vents to be within 10 feet of thermostats, and this close proximity is to ensure that the heat pump is taking in air that closely matches the temperature that’s displayed on the thermostat. In order for the heat pump to work properly, the thermostat needs to be able to accurately assess what the ambient temperature in the room is.

A heat pump can usually increase the ambient temperature by 15 to 20°F, but it won’t be able to do this if the thermostat is not determining the room’s temperature correctly. Return vents come in different shapes and sizes—and as was mentioned earlier—most are bigger than supply vents. There’s a direct correlation between the size of your return vent and how much air your heat pump needs to operate efficiently.

Determining Which Air Filter Is Best for You

To understand which air filters are best, you first need to understand the Minimal Efficiency Reporting Value, or MERV, rating that most air filters carry. A MERV rating of 1 means that the filter is pretty much ineffective, while a rating of 16 means that the filter is highly efficient. Most air filters have the MERV rating printed right on the packaging, so if there isn’t a rating present, then you can assume that the air filter is probably low-quality.

In general, air filters that carry a MERV rating of 13 to 16 are highly efficient, and therefore they aren’t suitable for standard heat pumps. The good choices for these heat pumps are filters that possess a rating of 8 to 12, as these can reliably capture a wide array of airborne contaminants. If you’re operating a higher-grade model than a standard heat pump, then you’ll probably have luck with 13 to 16 MERV-rated air filters.

There are four common air filters out there now, and each one is briefly explain below.

1. Disposable Flat Fiberglass

Generally, these air filters are rated 4 or less on the MERV scale. The are the most affordable kind of air filter and they require replacement every 30 days. These filters are ideal for those who prioritize cost saving, but they aren’t the best when it comes to providing good filtration. Therefore, you need to weigh the benefits of good filtration against cost before you purchase a disposable, flat-fiberglass return vent air filter.

2. Disposable Pleated Filters

These filters are quite common nowadays, and some possess a MERV rating as low as 4 while others have one as high as 12. Filter price is typically based on the MERV rating, and another factor that determines price is the amount of contaminants the air filter has been shown to capture.

If you have disposable, pleated return vent air filters, you can expect to replace these every 30 to 90 days. These filters are ideal because they are widely available and priced well, particularly those that are in the 6 to 8 MERV range. Moreover, because the rating range is wide, these filters are ideal for those who want to use high-grade filters in certain places and low-grade filters in others; this is a move that large commercial businesses sometimes make.

3. Electrostatic Filters

These filters are unique in that they can either be disposable or permanent. The ones that are permanent should be washed routinely, as doing so ensures they last a long time, sometimes as long as eight years. These filters utilize static electricity. Specifically, they charge air contaminants as they pass through, causing the contaminants to stick to the fibers of the filter.

Disposable electrostatic filters, on the other hand, are funny because they actually become more effective as they age. That’s because the build up of particles helps with blocking new particles.

This, however, isn’t the case for a permanent electrostatic filter, as here buildup makes the system less effective. For this reason, it’s important to know which kind of system you have, as each system requires a unique method of operation.

4. High-Efficiency Pleated Air (HEPA) Filters

High-efficiency pleated air filters, or HEPA filters as they’re commonly known, are thicker than the air filters which go in return vents. Generally speaking, HEPA filters are located inside the ductwork, making these harder to maintain. A professional HVAC maintenance team, however, will have no problem cleaning and maintaining HEPA filters for you.

HEPA filters are typically found in hospitals, laboratories, and other places that require the very best in filtration. Throughout the Covid-19 crisis, businesses that used these filters were regarded as superior, as it was shown early on that HEPA filters effectively eliminated widespread transmission of Covid-19. Also, HEPA filters are included on most, but not all, airlines nowadays.

Does Every Room in Your Home Need a Return Vent?

Homes being constructed now typically utilize only one return vent and one thermostat, but back in the day homes were constructed with multiple return vents and supply air vents in each room. If you currently own an older home, and you have a lot of air vents around, then in all likelihood there’s a central location from which the air comes.

Locate this spot, as this is probably where the heat pump is. Once the heat pump is located, you’ll need to find the slot for the filter. A lot of heat pumps, especially those that are split systems, will have a filter slot near where the return duct connects to the air handler.

Place the filter in the slot, wait an hour or so, and then come back to see if any contaminants have collected. If so, then you’ll know the filter is positioned correctly.

If you don’t know how to change out the air filter on your system, consider this guide. Or you can contact an HVAC professional and they’ll do this for you.

Blocking the Return Vent

A lot of homeowners find return vents to be visually unattractive, and for this reason some try to hide their vents behind furniture, pictures, curtains, and other fixtures. Concealing a return vent is never a good idea, as the return vent is a very important component for your home’s heating system.

If the return vent is obstructed, then it’s quite likely the heat pump won’t work properly. Specifically, blocking the return vent can prevent the heat pump from getting an accurate read of the ambient temperature. If the temperature can’t be read, then hot air can’t be produced.

Furthermore, if the system is continuously receiving an inadequate air supply, then it won’t run as it’s supposed to. Eventually, break down will be the consequence of poor operating conditions.

How a Heat Pump Is Supposed to Work

A properly working heat pump will have blower fans that suck up the air through the return vent. Once this air crosses the evaporator coil, it will be blown out of the supply ducts. If the vent isn’t able to suck up enough air, then there will be pretty much no airflow coming from the supply vent; this will strain the system over time.

Also, you should ensure that your supply vents are never blocked, as warm air can back up here and eventually become problematic. If you’re finding the return vent to be an eyesore, then perhaps you should get a decorative grill, as these can boost appearance without obstructing airflow.

Related Questions

Since every home and business utilizes some kind of heating system, a lot of individuals have questions about filtration, airflow, air quality, etc. Some of the common questions that are related to this topic are answered below.

Can supply vents have filters?

Yes, filters can be placed on supply vents as well. In fact, putting a filter on a supply vent is a lot more common than using one on a return vent. This is the best place for filtration, according to some experts, as supply vents only blow out. Return vents, on the other hand, run the risk of inhibiting airflow when there’s a filter present.

Is DIY filter installation recommended?

Yes, you can pursue DIY filter installation, but getting professional assistance is better. Professional assistance will ensure your filter gets set up right, and this will also provide invaluable peace of mind.

Furthermore, some systems are more intricate than others, and the complex systems tend to make filter installation a little more difficult. Hiring an HVAC professional to install the filter definitely won’t take a lot of time, nor will it cost a lot of money.

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Final Word

The most important takeaway is that a return vent filter can ensure a heat pump works better, as it’ll prevent the system from being affected by contaminants and other things that can be floating around in the air. However, a filter can obstruct the system, and obstruction creates a whole different problem entirely. Get advice from a professional HVAC technician so you can know what’s best for your system.

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Matthew Mountain
Matthew Mountain

Matt loves everything DIY. He has been learning and practicing different trades since he was a kid, and he's often the first one called when a friend or family member needs a helping hand at home. Matt loves to work with wood and stone, and landscaping is by far his most favorite pastime.

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