MERV stands for Minimum Efficiency Reporting Values and is an industry-created standard that evaluates the efficiency of air filters. The MERV rating of any particular air filter ranges on a scale of 1 to 16, with a filter rating 1 being the least efficient and a filter rating 16 being the most efficient. For example, a filter with a MERV rating of 3 would only be able to remove a small percentage of the largest airborne particles, while a more efficient filter with a MERV rating of 15 would remove even the tiniest airborne particles.

While it is important for the quality of the air in your home to choose the most efficient filter possible, it is not always as simple as buying a filter with the highest MERV rating. Because the pores allowing for air flow in a highly-rated MERV filter are very small, the filter creates more resistance against air flow and may put too much pressure on the fan of your furnace or air conditioning unit. It’s important to choose an air filter with the highest MERV rating that your particular unit will allow for maximum air flow. Information about specific MERV ratings and recommendations for your furnace will generally be included with the documentation that came with your system.

We recommend choosing an air filter with a MERV rating between 8 and 11 for most residential furnace and AC units in order to adequately remove airborne contaminants. If your system can handle a filter with a higher MERV rating, you may wish to use a filter with a rating of 12 or 13 for even greater contaminant removal. However, it’s important to remember that filters with a higher MERV rating must be replaced at least every three months to avoid restricted air flow and negative effects on your furnace’s performance.

Changing your filters regularly and using the most efficient filter possible for your furnace is the best way to control the air quality in your home and maximize the lifetime of your heating and cooling unit. A little research into MERV ratings will certainly pay off – in better health and improved appliance efficiency.