How do you know how effectively an HVAC air filter will safeguard your indoor air quality? The MERV rating was designed to provide a quick basis of comparison between different filter types. Expressed as a number between 1 and 16, MERV actually stands for Minimum Efficiency Reporting Value. The higher the MERV rating for a filter, the more efficiently the filter performs.
As long as your air conditioner or furnace is running, it’s pushing air through the HVAC air filter. In a typical day, all the air inside your home circulates through the ductwork and filter multiple times. That’s why the quality and efficiency of your air filter matters. Here’s how the various MERV filter ranges stack up by comparison:
Usually, the least expensive fiberglass panel filters that perform the least efficiently. Typically, these filters remove only the largest particles of dust — the stuff you can actually see — from the air. Smaller invisible particulates, which make up the majority of indoor pollution, escape filtration. Most HVAC professionals recommend immediately replacing them with a higher rated filter.
The most appropriate filter choice for most households, this range is dominated by quality pleated cotton or polyester filters. They will remove airborne particulates down to a size of 3 microns. This comprises all lint and dust, pollen, dust mites, and mold spores. Filters in this range offer the best balance between filtration efficiency with minimum airflow restriction.
If some family members have a particularly high sensitivity to certain airborne allergens, these filters provide an extra level of protection. They will remove 80 percent of airborne particulates down to a size of 1 micron.
This high-efficiency range is generally limited to hospitals, clinics and other commercial systems where HVAC systems incorporate high-speed blowers and high-volume airflow. For typical residential systems, however, these filters are too dense and excessively restrict airflow, causing poor cooling/heating performance and reducing energy efficiency.