What is a MERV Rating?

Changing your furnace filters regularly and using the most efficient furnace filters on your heating and air conditioning units are the first two steps toward improving your indoor air quality. In fact, the only way to actively reduce dust particles and airborne bacteria is through the use of efficient air filters. When choosing air filters for your heating and air conditioning units, it is important to buy the most efficient filter that your system will allow. Finding the most efficient filter possible is easy, thanks to the Minimum Efficiency Reporting Values, or MERV rating.

The MERV rating is an industry-standard system for rating the minimum efficiency of air filters. The MERV rating is a scale from 1 to 16, with one being the least efficient designation and 16 the highest. For example, a simple fiberglass panel would have a MERV rating of 5, and only traps the largest of airborne particles. A more efficient filter with a MERV rating of 14 will trap even the most miniscule particles.

Shopping for an air filter is not as easy as buying the model with the highest MERV rating, however. Filters with a higher MERV rating also create more resistance to airflow through the filter. The high resistance that comes with the increased MERV may tax your heater's fan power too extensively. Be sure to select a filter with the highest MERV rating that your unit's fan can maintain.

Also, some filters may use an electrostatic charge to improve their MERV rating. These filters offer a high MERV rating, but their efficiency dwindles as the filter absorbs contaminants. Look for a "discharged MERV" rating to find the filter's actual efficiency.

Taking a little extra time to learn about and inquire as to MERV ratings will pay off in the long run, as you will be able to choose the most efficient filter for your home.