What is a MERV Rating in Home Air Filters?

As air travels throughout the home it picks up dust particles, pollen, pet dander – you name it. Many residential air-conditioning units recycle the air that already exists in the home instead of pulling air from the outside. This means those dirty particles cycle right back into the home, polluting your air quality and causing a wide range of nasty symptoms from coughing to sneezing, to asthma, carbon monoxide poisoning and other problems.

Because of this, each AC unit has a filter you can easily change yourself or have installed professionally. Air filter replacements are available at almost any home improvement store, or through a subscription service like CleanAir.

The question is, how do you know what air filter to get? And you wonder, “What is a MERV rating in home air filters?”

Home Air Filters are Not Created Equal

There are so many filters on the market that it can be confusing to the average buyer. Many of us believe that every home air filter is created equal, which may be why our seasonal allergies are so bad, even when we seek refuge indoors.

After all, all air filters look the same, so surely, they all capture the same amount of dust in the air. Right?

That is not quite the case. There is a standard rating that manufacturers use to rate each filter called the MERV rating.

In this article, we discuss what a MERV rating is, how it affects your home air filtration system, and what MERV-rated filter you should use based on your in-home needs.

What Exactly is MERV Rating?

MERV is an acronym that stands for Minimum Efficiency Reporting Value. This is a rating system used to quantify how efficient a home air filter is at capturing different particles in the air based on their size.

The higher the MERV rating, the finer the mesh and the higher air filtration capabilities the filter has.

Higher air filtration capabilities in your home mean your air will feel fresher your, your AC unit will run more efficiently, and there will be healthier living conditions.

Keeping your home clean can provide several benefits. (1) These benefits range from reducing the allergens present in your home’s air, to maintaining the lifespan of your AC unit and reducing your carbon footprint, to keeping the environment a little cleaner.

Best of all, with an indoor air filter that suits your needs, you won’t need those allergy pills nearly as often. A good air filter reduces the number of allergens in your home, even if you have pets. This helps reduce your symptoms and keeps you comfortable in your own home.

“For people who suffer from outdoor allergies to ragweed or grass, the best solution is to stay indoors, especially in the morning when pollen counts are highest, and to seal the clean air in. 'Central air conditioning is best because they can keep windows closed and that prevents some of the pollen from coming in,' " - Ganda Suthivarakom, Wirecutter

The MERV rating has become a standard in the air filter industry. This MERVE rating is assessed by its ability to capture particles in the air that are between 0.3 and 10 microns in size.

For reference, one micro is roughly a twenty-five thousandth of an inch. These particles that are in the air around us are invisible to the eye. Occasionally, we’ll see dust particles floating in the right lighting, but these particles have a very real effect on our health.

There is a limit to the efficacy of your air filtration system and how much it can handle. For most in-home air filtration systems, it’s recommended to have an air filter that ranges between 8 and 13 on the MERV rating scale. CleanAir offers MERV 8 air filters, MERV 11 air filters and MERV 13 air filters.

How Does the MERV Rating System Work?

The U.S. Environmental Protection Agency has produced a chart that sets the standard for the MERV rating that helps de-mystify the rating scale for the average home consumer. (2)

Of course, most of us do not own a microscope that will allow us to look directly at a micron, but we can feel the difference in our lungs and how much better our AC unit works after a filter replacement.

“The rating is derived from a test method developed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE)” - EPA.gov

This standardized rating is a great way to determine the quality of your air filter, but it is also important to find the right filter for your unit. An air filter with a high MERV rating can be just as detrimental as one that’s too low.

The MERV rating is determined based on the average particle size efficiency in microns. The lowest MERV rating is 1-4, which captures less than 20% of all particles that make their way through your air conditioning unit.

The median MERV rating is 10, which captures between 64% and 85% of all particles that make their way through your home’s air ducts. This is the standard for most quality AC units.

The ideal MERV rating is 14, which can capture up to 90% or more particles that move through your air filtration system.

Of course, the material your air filter is made with is also important in filtering out air particles. The EPA recommends a HEPA filter, which is made with a durable, pleated material.

CleanAir provides MERV 8, MERV 11 and MERV 13 pleated filters are made in the USA. You can choose any of these filters as a part of your subscription service and have them delivered directly to your home for free. These filters are recommended based on your lifestyle, number of occupants, level of air pollution and number of pets in your home.

Is a Higher MERV Rating Always Better?

It is true that a higher MERV rating filters more particles out of the air than a filter with a lower rating. It is also true, however, that your AC unit may not be able to handle filters with a higher MERV rating, which will potentially clog the system if you have not changed the filter in years.

Likewise, the higher the MERV rating, the finer the mesh, which means you will need to change your filters sooner because they are easier to clog with finer dust and dirt particles.

Your AC unit will have instructions that state the MERV rating it was designed for and going any higher than the maximum recommended rating will reduce the air flow in your system. The air cannot pass through mesh that is too fine for the unit, causing damage the unit and harming your indoor air quality.

Most residential AC units can only use filters up to the MERV 13 range. Higher MERV ratings are commonly used in commercial settings such as hospitals or construction shops where it’s necessary to filter out smaller particles, including bacteria and viruses.  

It’s best to do your research on what filter your system needs prior to upgrading or changing air filters or contact a certified HVAC specialist to help you.

Is MERV 8 Good Enough?

In many cases, MERV 8 is the median recommended filter that most in-home units can handle, making it an excellent choice that balances both filtration quality and performance.

MERV 8 air filters have been proven to capture everything from mold spores to ozone, and to hairspray or other aerosols, dust mites and pet dander. This is an excellent budget choice for residential homes, and it does its job well to filter dander, dust and other common allergens.

If anyone in your family suffers from chronic indoor allergies, however, or if you have more than two or three pets, you will want to invest in a MERV 9 filter and up, so long as your unit is approved to handle the filter.

Does Filter Size Affect MERV Rating?

Some say the filter size can affect your filter’s MERV rating, and that smaller filters are overall better. This is not the case.

The width and length of your air filter does not affect the MERV rating, and your home will be just as protected with a large air filter as it will with a smaller filter. Your air filter’s rating is based on its capability to filter particles from the air in any set of dimensions.

In other words, a 12-by-24 air filter with a MERV rating of 9 will prevent the same size particles from re-entering your home that a 20-x-30 air filter will. There is no loss in efficacy, and your home will be just as protected.

The only affect air filter size has on your home air system is what size the unit requires to have a complete seal and properly filter particles from the air.

MERV Rating VS. MPR

You know what a MERV rating is, but your current air filter states an MPR rating.

So, what is an MPR rating?

MPR stands for Micro-Particle Performance rating. It is a rating system that was developed by 3M, a company that produces air filters and other home maintenance products. Like the MERV rating, it rates how efficiently air filters can trap particles smaller than one micron.

“The MERV rating is a standard in the air filter industry, and it is typically assessed by particles between 0.3 and 10 microns in size.”

This means that, while MERV is the industry’s standard, it tests a wider range of particles. Common allergens such as dust tend to range from 0.2 microns in size and larger, while pollen and pet dander can range from 7 microns and larger.

MPR ratings range from 100 to 2800, giving residents a greater range of options based on their needs. While MPR 100 is proven for lint and household dust, MPR 1500 filters are considered the median filter that captures everything from lint to pet dander, smoke and viruses.

Higher-end MPR filters are even capable of capturing exhaust particles, making it an excellent choice for homes with an attached garage or carport.

The main difference between the MPR and MERV rating systems are that MPR focuses only on microscopic particles, while MERV tests larger particles.

 

References

  1. New York Times
    https://www.nytimes.com/wirecutter/blog/how-to-minimize-allergies/

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