Understanding What MERV Ratings Mean for Air Filter Efficiency

Posted On: June 06, 2014

Understanding the minimum efficiency reporting value (MERV) for HVAC filters will help you select an appropriate furnace or A/C filter based on the needs of your household without sacrificing heating and cooling performance.

MERV ratings range between 1-16 (with 17-20 reserved for High Efficiency Particulate Arresting, or HEPA, filters). As a general rule of thumb, filters with MERV ratings of:

  • 1-4 will remove the largest dust particles. Although filters with this rating will protect the machinery inside your HVAC system, they do little to improve your indoor air quality (IAQ).
  • 5-8 will remove mold spores, animal dander, smaller dust mite debris, etc. Filters in the higher end of this range will help those who suffer from allergies or asthma.
  • 9-12 remove smaller dust particles from lead, milled flour, etc., as well as particulates from auto emissions and some smoke particles. Filters with these numbers are suitable for homes with people who are sensitive to IAQ as well as some hospital settings.
  • 13-16 remove airborne bacteria, most smoke particles, insecticide dust, paint particulates, etc. These filters are appropriate in standard hospital surgery settings. If used in a home HVAC system, your equipment likely will need serious modifications to accommodate the denser filtration media and larger size of the filter.

Choosing the right air filter is an important step to improving indoor air quality and keeping your HVAC system running at peak performance. Filters with higher MERV ratings are not necessarily better; their small pores may reduce the air flow moving through your HVAC system and compromise the machinery inside, reducing system efficiency.

  • Disposable fiberglass filters with a MERV 1-4 rating are inexpensive and useful for if you’re mainly concerned about protecting your HVAC equipment and components.
  • Disposable pleased filters with a 6 rating can improve IAQ but must be replaced frequently.
  • Disposable electrostatic filters with MERV 10 are excellent in homes with smokers and sensitive people.
  • Permanent electrostatic filters with a MERV 8 will improve IAQ and last six to eight years with regular cleaning.
  • High-efficiency pleated filters with a MERV 14-16 are generally used in hospitals but may be helpful in homes with people who are extremely sensitive or ill.

Homeowners in Troy, Collinsville and other Southwest Illinois towns who would like more information about choosing an appropriate HVAC filter should contact the friendly staff at Ernst Heating and Cooling today.

Our goal is to help educate our customers in Edwardsville, Collinsville, Maryville, Staunton and Troy, Illinois about energy and home comfort issues (specific to HVAC systems). For more information about MERV ratings and other HVAC topics, download our free Home Comfort Resource guide.

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