What is MERV?

HVAC filters help your heating and cooling units run at peak efficiency while providing your home with clean, quality air. Filters use MERV ratings to indicate the performance level of the filter. But, what exactly is a MERV rating and what makes one rating differ from another? We’ve got your answers right here.

What is a MERV rating?

MERV DefinitionThe American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) designed the MERV rating system with ratings ranging from 1 to 16. As the numerical rating increases, so does the filters ability to trap smaller and smaller airborne contaminants. For example, a filter with a MERV rating of 13 will be able to trap more particulates than a filter with a MERV rating of 4.

Does a Higher MERV Rating Mean a Better Filter?

Generally, yes.  A filter with a higher MERV rating will be able to remove smaller particles from the air passing through it.  This means the air you breathe will be cleaner. Use the chart below to better understand the impact of a MERV rating.

MERV Chart

Filtration Levels

Different filtration levels coincide with the different MERV ratings. We want our customers to find the right filter to fit their needs. Read through the different levels of protection to find the correct filter for your home.

Basic Protection

Filters with MERV ratings between 1 and 4 provide the most basic filtering protection. These filters are designed to protect an HVAC unit’s coils from becoming coated with dust and dirt, but are not efficient at removing allergens from the air or improving the quality of air in your home. Filters rated MERV 1 through 4 are the most budget friendly and can be found in multiple disposable styles and sizes to fit many HVAC units as well as window air conditioners.

General Filtration

Air filters with a MERV rating of 8 will remove more particulates and typically last longer than a filter with a MERV rating of 4. Much like filters with a MERV 4, MERV 8 filters will remove dust and dirt, but will also capture pollen, some mold spores and other particulates. Trapping these airborne impurities can help improve a home’s air quality, especially for anyone suffering from dust and pollen allergies. MERV 8 filters provide great filtration for those on a budget.

Filters for Pet Owners

Pet dander can cause more allergy problems than flyaway fur can. A filter with a MERV 11 rating will capture the majority of that dander. An air filter that can trap and control the amount of pet dander and other allergens circulating through an HVAC system can be a powerful tool in the battle against allergies. This type of filter will also last longer and make your HVAC system run more efficiently than lower rated filters. Though an air filter with a MERV 11 rating will remove more particulates than lower rated filters, those with severe allergies or asthma may want a filter with an even higher MERV rating.

Maximum Filtration

For those suffering regularly from allergies and/or asthma, a filter with a MERV rating of 13 or higher may drastically help improve your indoor air quality. Filters with high MERV ratings reduce airborne impurities such as dust, dirt, pollen, mold spores, pet dander and more from your home’s circulating air. Not only does a highly rated filter remove impurities, but it lasts longer than other filters and also helps your HVAC system run more efficiently than a lower rated filter. Though highly rate filters may cost more than other filters, the high quality filtration you receive is worth every penny.

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Remember, when shopping for new HVAC filters; always keep the MERV ratings in mind. Whether you’re looking for a new air filter on a budget, or looking for maximum protection, MERV ratings will tell you which filter is right for you. It should be noted that the EPA states that filters rated between 7 and 13 may be near or as effective as some HEPA filters.

 

7 thoughts on “What is MERV?

    1. Katie Post author

      Hello Dan,
      Thanks for reaching out to us. Here you can find our 20x26x5 filters-http://www.discountfilters.com/air-filters/20x26x5/. Let us know if you need any more help!

  1. Jeffrey Schnabel

    How does MERV rating affect CFM? That is, if I want a 16×25 filter, how do I figure the CFM for each type of filter MERV rating available? I need a specific minimum CFM for the size of HVAC system I have.

    Does CFM change with a thick pleated filter compared to a thinner one, if they have the same MERV rating? That is, if I have a MERV of 11, is the CFM the same for a 4″ or 6″ thick filter, compared to a 1″ with the same MERV 11 rating? It seems the thicker filter has more surface area and hence maybe an ability to handle more air.

    1. Katie Post author

      Jeffrey,
      The CFM between different MERV ratings should be equal because the filters with the higher MERV rating will have more pleats, which will create more surface area and compensate for the denser filter media. In the case of comparing filters by thickness, the same set of basic principals apply.

      However, since the 4 and 6 inch filters have much more surface area than a 1 or 2 inch filter they typically will be recommended to change every 6 months. 1 and 2 inch filters are typically changed every 2 or 3 months.

      Hope this answers your question!

      1. Jeffrey Schnabel

        Hi Katie,

        I found a very informative article, with what appears to be sound testing methodologies, and the results are pretty interesting. You might want to review it –
        http://www.homeenergy.org/show/article/id/667

        In summary, if the blower motor is a PSC motor (it doesn’t change speed based on air flow restrictions), then generally speaking, a higher MERV rating results in less air flow. Whereas a blower motor based on ECM technology will increase speed to account for the higher air restriction of higher rated MERV filters, and consume more power as a result, albeit considerably less power than a similar configuration using a PCM motor. So for ECM based systems, it seems a higher MERV rating will result in higher electrical costs to run the motor, but will not result in lower air flows.

        The test results also show that higher MERV ratings among different filter manufacturers, do not necessarily have similar flow rates.

        Thanks,

        Jeffrey

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