Does a MERV 8 Filter Restrict Airflow?

There is a lot of confusion surrounding the MERV rating of air filters, especially from new homeowners in the Dallas-Fort Worth area. You might not be sure what your previous filter was rated, or you might be looking for a better option.

Most often, if you are looking for a higher MERV filter, you just discovered the filter you were using was inadequately cleaning your home’s air. Pleated air filters are by far the best choice when you want to get the best clean out of your home unit, but did you know that you might be doing your home’s air quality a disservice by purchasing the highest MERV rated filters?

That’s right. There’s a limit to what your unit can handle, and a maximum level of efficiency when the filter stops cleaning your home’s air.  

Diving into the details of home air quality can be confusing when the rating varies so wildly depending on the unit’s strength.

In this article, you will learn about MERV ratings and how it affects your filter’s efficiency. You will also learn about the ideal MERV rating for residential units, whether an air filter can be too restrictive on your system, and how to tell what strength filter your unit can handle at a maximum.

Do Higher MERV Filters Restrict Airflow?

If you’re like many people, you choose the least-expensive fiberglass filters in the HVAC aisle and only replace your filter every three months. For many, that used to be what came suggested as the standard guidelines for homeowners who changed their own air conditioning filters. We know now that advice was incorrect.

If you switch to a pleated air filter, you may not know what to look for in a MERV filter. The higher rating, the better, right? So, you pick up a MERV 13 air filter for your small three-bedroom home.

Next thing you know, your AC unit is running higher, driving your electricity bill into the sky, and your filter is dirty, and it has only been a week. What went wrong?

While it's great you upgraded you air filter, you need to upgrade how often you replace your filter as well. MERV 13 pleated filters are the highest rated filter recommended for a home because they filter out the most particulates. However, because of their tightly woven fabric, they will capture more particulates faster which causes your filter to need to be replaced more frequently. To ensure you are optimizing you AC unit's energy and the filter's capabilities, change your MERV 13 filter every 30 days.

What is a MERV Rating?

A MERV rating is a rating assigned to each air filter signifying its ability to capture particles up to a certain size. (1)

“The higher the MERV rating the better the filter is at trapping specific types of particles.” - EPA.gov
 

Generally, MERV ratings range from 1 to 16. MERV 1 is the largest filtering capabilities for any unit, common in fiberglass filters where there is little in the way of protection against dust. These filters are best for workshops and factories where large debris might need to be captured and is generally the first line of defense before the air is routed to another AC unit to capture dust and debris.

Fiberglass filters with a MERV rating between 1 and 4 are not suitable for the home and will not help your unit capture fine dust and debris.

MERV rating 4 and beyond are generally available in pleated air filters, which are the best choice for residential and indoor commercial air filter units. These are more efficient at capturing the small dust particles in the air without restricting air flow.

MERV 6 is effective at capturing about 50% of all dust particles that blow through the average home. This filter rating isn’t ideal for homes with more than one person, especially not if any of the occupants are prone to allergies. These filters are also not recommended for homes with pets because pet dander may not be trapped and filtered out of the home.

MERV 8 is the sweet spot for many residential units, trapping an average of 85% of all common dust particles and filtering them out of the home without being too restrictive on the unit’s airflow, keeping your energy bills low and your home cooled.

A residential home may go up to a MERV 11 without any significant decrease in efficiency if the home has a larger AC unit, if any occupants have allergies, or if there are animals present in the home. MERV 11 filters will help keep the unit free of debris and running efficiently, but these filters will need to be changed more often than their MERV 8 counterparts.

HEPA filters are another type of filter that typically comes in higher MERV ratings, but these filters are only suitable for high-traffic commercial buildings or medical offices. These filters are effective at trapping bacteria from viruses and other biological hazards.

Does a MERV 8 Filter Restrict Airflow?

MERV 8 filters are excellent at filtering out pollen, pet dander, and finer dust and debris than many other filters. These are the best option for most residential homes, but with everything, there are exceptions.

Does a MERV 8 filter restrict airflow? Not really.

In general, a MERV 8 filter is perfect for a residential air conditioning unit with no previous issues or damage and in a moderately-sized home.

Every AC unit is different in how it filters dust and what type of air filter it needs to operate at maximum efficiency. Even two units of the same brand and model have unique qualities that change how well they run. Age and previous maintenance are two of main factors that change how well your AC will run with a MERV 8 filter.

If you just installed your unit, then it may run efficiently with a MERV 8 filter, cleaning your home with the vigor of new machinery.

If your unit is old and will require heavy maintenance soon, MERV 8 filters might be too restrictive on the airflow. You may find yourself changing the filter every other week, or even every week, depending on how dirty it gets between cycles.

This is normal for homes with a high occupancy and pets. But for homes that don’t see a lot of foot traffic, for example, if you are at work for most of the day, there may be good reason to switch to a MERV 8 filter and see how your home’s air quality changes.

Likewise, if your unit has been poorly maintained, it is less likely to respond well to higher MERV ratings. The internal mechanisms in your AC unit can be sensitive to clogs and dust once they have sustained damage.

Damage can be caused by everything from leaving a dirty air filter in too long, to forgetting to put a new filter back in. This damage can affect the longevity of your unit, causing it to get clogged more easily, leading to poorer function and a need for a filter with a lower MERV rating. These units will not clean your home’s air as efficiently.

How to Choose the best MERV Rating for Your AC

It can be difficult to get a straight answer about what MERV rating is best for your AC, especially if you are uncertain about the history of your HVAC unit or how it has reacted to higher MERV rated filters in the past.

Fortunately, there is no need to fret too much about your unit’s MERV. You can often tell by how quickly the filter gets dirty and how your electricity usage fluctuates.

If you want to learn how to choose the best MERV rating for your AC from the start, take a look at the unit in your home.

The unit itself will not tell you what MERV rating to purchase, but it will tell you what size air filter you need to purchase.

Start at a baseline of a MERV 8 and consider how hard your filter will have to work. Are there multiple people in the home? Pets? Then try a MERV 11.

Is anyone in your home prone to allergies? Better bump that MERV rating up to a 11 or 13, depending on the severity.

There’s no need to purchase a deeper filter than what your unit uses. (2) Start with the recommended depth on your unit.

 

“[…] they didn't see as much difference as they expected for filters of different depths.” - Allison Bailes

 

How deep your filter is doesn’t play a strong role in your home’s air quality. This is mostly a factor in how well the filter fits deeper units.

Join CleanAir Today

CleanAir is the top choice for residents in the DFW area, with home air filter deliveries scheduled at your fingertips. Choose from several different types of filters with different MERV ratings to suit your needs, then choose your delivery frequency.

Before you know it, you will be enjoying clean air throughout your home, and you won’t have to remember to buy a filter ever again.

Can’t change your filter yourself, or don’t want to? We have your back. We also offer professional installation services scheduled at your convenience. Our air filter experts have been changing air filters for Dallas residents for years and are familiar with every type of HVAC unit.

Ready to schedule your first air filter delivery? Join CleanAir today!

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References

  1. Environmental Protection Agency
    https://www.epa.gov/indoor-air-quality-iaq/what-merv-rating-1

  2. Energy Vanguard
    https://www.energyvanguard.com/blog/do-high-merv-filters-always-reduce-air-flow