what is a MERV rating?

What’s a MERV rating anyways?

Shopping for replacement air filters for your air conditioning system can seem complicated. Big box stores offer a range of options in many sizes and prices, but what are you actually buying? Many folks resort to replacing their worn-out filters when it’s long overdue and do not put much thought into the air filters they buy as replacements. Fortunately, with a little bit of information, the filter buying process can be informed and efficient. 

At Discount Filters, we offer an array of furnace filters in all sizes, as well as custom sizes. Once you know the size filter your HVAC requires, you’ll need to decide which filter type you need. One rating system that is used across the industry is the Minimum Efficiency Reporting Value or MERV. 

MERV Rating, Defined

MERV is a measure of the effectiveness of an air filter at capturing and removing particles from the air that passes through it. Ratings range from 1 to 20, with higher numbers indicating better filtration performance. Households that have members with allergies or health concerns may benefit from a higher MERV rating air filter. The AirX allergy filter, for example, has a MERV score of 11, while the AirX health filter has a MERV rating of 13. 

The MERV rating system was developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) to help consumers and HVAC professionals compare the performance of different air filters. The MERV rating considers the filter’s ability to capture particles of different sizes, with higher MERV ratings indicating better capture of smaller particles such as pollen, dust mites, and bacteria.

What do the MERV ratings really mean?

MERV 1-4

Air filters with this rating provide minimum protection. The filters are flat and made of fiberglass, and catch particles at least 10 microns and up. Pollen, dust mites, and roach debris are the type of particles trapped by this filter. Low MERV rating air filters don’t last as long as the better filters, and do little to improve indoor air quality.

MERV 5-8

Air filters with MERV ratings of 5-8 are medium-quality filters that trap between 20 and 70 percent of particles larger than 3 microns. This includes pet dander, mold spores, and dust mite droppings. According to the U.S. Environmental Protection Agency, filters with MERV ratings of at least 7, are almost as effective as HEPA filters when it comes to removing hazardous pollutants.

MERV 9-12

Furnace filters with MERV ratings between 9-12 are the best-quality air filters that an unmodified residential HVAC system can accommodate. These air filters trap up to 90 percent of particles between 3 and 10 microns and up to 70 percent of particles between 1 and 3 microns. A filter of this quality can help control or minimize COPD, allergy symptoms, and asthma attacks.

MERV 13-20

HVAC filters with MERV ratings between 13-20 are used by hospitals and manufacturing operations. These air and furnace filters remove particles down to .3 microns, including all bacteria and viruses. Residential systems will require modification to accommodate filters with these ratings.

MERV Rating must match air conditioning filter specifications

However, it is essential to note that higher MERV ratings also mean that the filter may restrict airflow more, which can negatively impact the performance of your HVAC system. You may want to consult with a professional to determine the appropriate MERV rating for your specific needs and air conditioning system. The proper balance between your indoor air quality needs and your system’s airflow will prevent overheating and ensure peak efficiency. 

While higher MERV rated filters may cost more, don’t let the price discourage you from using the best filter possible. Buying in bulk and/or signing up for an air filter subscription are two ways to save money and time while also attending to your air conditioning system. Discount Filters, on average, will save you money and work just as well as their higher-priced counterparts.

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