Discover the purpose of MERV Ratings for air filters.

If you’re like most homeowners in Ontario, you might not know much about MERV ratings. That’s understandable because the cheap, one-inch air filters you can find at a local store appear to do a sufficient job cleaning your air. The truth is, however, that they do a poor job of removing particles from your air and may actually be causing your energy bills to rise too.

You need to understand the importance of choosing the right air filters for your home, which means you need to have a good idea what minimum efficiency reporting value (MERV) ratings mean.

  • MERV 1-4: This is the range where most of those one-inch flat panel filters fall. These filters only catch particles down to 10 microns in size, which basically means they can remove some mold spores but don’t do much for bacteria, viruses and other pollutants.
  • MERV 5-8: These are the filters that are best for most homes. They have a pleated design that allows them to capture particles down to three microns in size without significantly inhibiting airflow. They’re able to remove all types of mold and mildew, along with many forms of bacteria and some viruses. Additionally, they last longer than the flat panel models because they keep particles on the surface fabric, rather than using the fibers inside the filter to hold them.
  • MERV 9-12: This the beginning of the commercial-grade air filters. They are able to catch particles down to one micron in size, like tobacco smoke, viruses and bacteria. That sounds ideal, but also they hinder airflow so they’re typically only used in homes with air quality concerns or by families with health problems.
  • 13-20: These filters, also known as HEPA filters, are industrial- and hospital-grade models and are only likely to be used in homes with severe air quality problems. They significantly hinder airflow, which causes your energy bills to rise, but may be necessary in specific situations.

{ 2 comments… read them below or add one }

Frances Archer February 16, 2013 at 8:23 am

Thank you for this timely information as I was planning on going to the store TODAY to purchase a new furnace filter. Great advise as I did not know this and have probably bought the wrong one everytime in the past but now that I am infomed I will make the smart decision.

Gillian Findlay February 16, 2013 at 1:23 pm

Great information on MERV Ratings for air filters for Furnaces – thanks for forwarding – I will certainly look into this the next time I pick one up.
Cheers.

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