MERV Rating 9-12 Filters in this range can trap more than 85% of particles with a size of 3.0-10.0 microns. A Merv 9 will trap less than 50% of the 1.0-3.0 micron size particles, MERV 10 will stop up to 64%, Merv 11 will get up to 79%, and MERV 12 is capable of trapping up to 89%. ASHRAE recommends MERV 6 or higher. The U.S.
Department of Energy recommends merv 13 LEED recommends MERV 8 as a minimum. Get current news, promotions and industry tips. While the highest merv ratings are the most effective for air quality, they can damage your HVAC system. If the merv rating is too high to be operated by the oven fan motor or air handler, the result will be low airflow.
The MERV rating of an air filter is a scale from 1 to 16 that describes the minimum efficiency of the air filter. Okay, let's go into the details of why a MERV blast furnace filter might not be good for your furnace. If your HVAC system uses a coarser filter (usually in the 4-inch to 5-inch range, and usually mounted on the air handler), it's likely designed specifically for medium-efficiency MERV filtration. If you are susceptible to allergies, asthma or other respiratory conditions, you may want to use a filter with a MERV rating of approximately 10 to 12.In addition, unlike HEPA, MERV tests measure particles of different sizes, from 0.3 microns (very small and difficult to filter the size measured by HEPA tests) to 10 microns (relatively large and easy to filter).
E1, E2, and E3 particulates are particle range sizes used in air filter testing to determine a MERV rating. While ASHRAE recommends MERV 13 and 14, it's best to select a filter with the highest possible MERV rating for your specific HVAC system. In addition, a MERV 12 filter that is only 1 (one inch) thick is likely to be more restrictive than a 4 (four inch) thick MERV 12 filter. With the lowest MERV rating (1-), the filter will continue to capture pollen, dust mites, cockroach debris, sanding dust, spray paint dust, textile fibers and carpet fibers.
For example, if an air filter can capture at least 20% of E1, 65% of E2, and 85% of E3 particulates, it will earn a MERV 11 rating. Some air filters, especially those with higher MERV ratings, may impede airflow due to improved air filtration. In simple terms, it sets the minimum amount of particulate matter that a filter must capture to achieve a specific MERV rating.