What Do the Different HVAC Filter Ratings Mean?

The heating and cooling world is filled with different types of ratings and their corresponding acronyms. We’ve got SEER for air conditioners, AFUE for furnaces, HSPF for heat pump heating, and more! When it comes to HVAC filter ratings, it’s all about MERV – which stands for minimum efficiency reporting value. Read on to find out what MERV means and how to find the right air filter rating for use with your heating and air conditioner system.

HVAC Filter Ratings Deal with Effectiveness

While the ratings you see on HVAC equipment such as furnaces and air conditioners reflect the unit’s energy efficiency in various ways, HVAC filter ratings measure the filter’s effectiveness when it comes to removing debris and contaminants from the air that circulates through it. MERV ratings tell consumers how well (or how poorly) the filter performs, and how effective the filter is at removing airborne particles of a certain size.

MERV was created in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and has since been used to show HVAC filter ratings. Air filters are tested by taking particle counts from the air volume using standard dust patterns over a set number of cycles. The MERV rating assigned to a filter reflects its arrestance, or ability to filter our synthetic dust; dust spot efficiency, which is the ability to remove atmospheric dust; and particle size ranges.

What Does a MERV Rating Mean?

The MERV rating scale runs from one to 20. One represents the lowest efficiency performance, while 20 represents the highest efficiency performance. The higher the MERV rating, the more efficient the filter. As MERV increases, so does a filter’s ability to capture small particles and more of them. Basic MERV charts show average particle sizes and their efficiencies for ranges of ratings, while expanded charts will show more details such as each rating’s efficiency at capturing various-sized particles.

Should You Choose the Highest MERV Filter?

When selecting a filter for use with your home’s HVAC system, the MERV rating must be considered. While you want to find a filter that offers efficient contaminant removal that is capable of controlling common contaminants in your home, you must be aware of the limitations of your HVAC system’s equipment. It’s easy to conclude that everyone should use MERV 20 filters at home because they are the best, but actually doing so can lead to serious problems.

The higher MERV rating a filter has, the smaller the pores are across the filter’s surface. Smaller pores give the filter the ability to capture smaller particles, but in turn, the filter’s makeup also creates airflow resistance. This means it is harder for air to circulate through the filter and into the HVAC unit.

Hindering airflow in the pursuit of superior air filtration is not wise. When heating and cooling equipment doesn’t receive adequate airflow, units can overheat, components can sustain damage, and the systems can experience difficulties keeping your home at a comfortable temperature. Thus, the HVAC filters with higher MERV ratings aren’t necessarily the best choice for your home or HVAC system.

HVAC Filter Ratings for Home Comfort Systems

In general, MERV measures for HVAC filter ratings are grouped as follows:

  • MERV 1 to 4: Basic filtration of particles between 3 and 10 microns in size, which are generally some pollen, dust mites, carpet fibers, and cockroach debris. These filters are used in home HVAC systems.
  • MERV 5 to 8: Improved air filtration for particles between 3 and 10 microns in size, which also includes mold spores, dust, pet dander, and lint. These filters are used in homes as well as commercial or industrial applications.
  • MERV 9 to 12: Some filtration of particles between 1 and 3 microns and up, including vehicle fumes, lead dust, and large bacteria particles. These air filters aren’t typically used in residential HVAC systems but may be used in home air cleaner systems, and can be found in some commercial buildings.
  • MERV 13 to 16: Offers filtration of particles between 0.3 and 1 microns in size and up, such as bacteria, tobacco smoke, sneeze particles, legionella, and mineral dusts. These filters are found in hospital environments that require high filtration.
  • MERV 17 to 20: Offers best filtration of particles 0.3 to 1 micron and up, with the ability to trap viruses, carbon dust, and all bacteria. These air filters are used in clean room environments.

Typically, MERV 8 is a good choice for home HVAC systems when it comes to HVAC filter ratings. With these filters, you gain better filtration for improved air quality, and they last longer than lower-rated filters. Your furnace or air handler owner’s manual should state the maximum HVAC filter ratings for use with your equipment.

Air Filter Help from Grove Heating & Cooling

If you have questions about HVAC filter ratings or selecting the right HVAC filter for your heating and cooling system, we’re here to help. Contact us today to discover the best filter for use in your Maryland home to improve the indoor air quality.