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MERV Ratings: Be Sure You’re Replacing Your Air Filters With the Right One

Changing your HVAC system’s air filter is both the simplest and most effective action you can take to improve efficiency and extend your equipment’s life span. But how do you know if you’re installing the right kind of filter? Learn how MERV ratings work to help you choose the best air filter to increase efficiency and extend the life of the system.

MERV

Minimum Efficiency Reporting Value (MERV) is a fairly straightforward system used to rate the efficiency of air filters used in air conditioners, furnaces, heat pumps and more. Filters are grouped into three basic categories.

  • Low-efficiency

Filters with a MERV rating of 4 or less are considered low efficiency, able to capture only the largest particles (10 microns in size or larger).

  • Mid-efficiency

Mid-efficiency filters range from MERV 5 to 13, and are generally the best option for residential systems. They trap particles from 3 to 10 microns in size.

  • High-efficiency

High-efficiency air filters are generally those with a MERV rating between 14 and 16, but aren’t suitable for use in most residential systems. These are generally employed in hospital settings or other clean environments.

HEPA

Don’t consider High Efficiency Particulate Air (HEPA) filters, which have a MERV rating of 17 to 20, as an option for use in your residential HVAC system, as their extremely dense filter fibers will damage your equipment. They probably will require an equipment retrofit anyway. Many homeowners, however, use HEPA filtration in stand-alone air-cleaning systems, in order to ensure pristine indoor air.

Airflow

While particle size is an important factor when choosing an air filter, airflow is also crucially important. High-efficiency filters may restrict the flow of air, putting undue stress on the HVAC system. Low-efficiency filters allow sufficient airflow, but only trap large particles. Mid-efficiency filters, it turns out, provide an adequate middle ground when it comes to trapping particles and providing sufficient airflow. In fact, experts believe these filters may prove almost as efficient as high-efficiency filters, because as they fill up with particles, their surface becomes denser.

If you have questions about MERV ratings, or any other home-comfort need, please contact us at Donald P. Dick Air Conditioning. We are proud to serve homeowners in the greater Fresno area.

Our goal is to help educate our customers in the greater Fresno, California area 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.

Image courtesy of Shutterstock