Air Filter Ratings

Most residential systems come with a panel filter rated MERV 1 to 4.  We recommend a pleated MERVE 12 filter for residential systems.

The first purpose of an air filter is to prevent airborne contaminants from reaching the evaporator coil.  The evaporator coil is normally wet from condensation and airborne dust will adhere to the coil.  Eventually air flow and heat exchange efficiency are reduced.

In recent years consumers and business owners have used the air filter to improve indoor air quality.  Caution must be observed when increasing the efficiency of air filters since higher efficiency filters also restrict air flow.  Many systems return air ductwork, RA grill and filter are sized marginally.  Any additional restriction from a high efficiency filter can starve the unit for air, resulting in decreased performance and efficiency.  Taken to extremes, the units compressor and supply air fan can be severely damaged.

Filters with additional surface area such as pleated filters can be used in some cases to increase filter efficiency without increasing the width and height of the filter.  Thickness will increase.  An example would be replacing a 25 x 25 x 1 panel filter with a 25 x 25 x 2 pleated filter.

MERV (minimum efficiency reporting value) ratings are used to rate the ability of an air conditioning filter to remove dust from the air as it passes through the filter. MERV is a standard used to measure the overall efficiency of a filter. Higher MERV ratings mean fewer dust particles and other airborne contaminants pass through the filter.

MERV ratings range from 1 – 16 and measurements are in microns. Some of the common particles related to MERV ratings are pet dander, insecticide dust, smog, dust, viruses, wood, tobacco smoke, spores, bacteria and pollen.

Some of the most common filters found in residential use only have a MERV rating of 1 to 4. These are typically disposable panel type filters and do not do a good job of filtering the air because they will not stop particles smaller than 10 microns.

MERV 5 to 8 rated filters are a better choice and are more commonly found in commercial applications. These filters will collect particles as small as 3 microns and are a good choice for home owners also.

Filters with a MERV rating of 9 to 12 are used in commercial and industrial applications and will stop particles in the 1 to 3 micron range. These filters are a great choice for home owners who want the best dust control possible.

The most efficient filters have MERV ratings of 13 to 16 and will stop particles as small as .3 microns. These filters are used in hospitals and other super clean environments.