Understanding the Pros and Cons of Different MERV Rated Air Filters

When selecting an HVAC air filter for your home or business it is essential to consider both its MERV rating as well as its ability to allow adequate airflow through your system without causing too much strain on your HVAC equipment.

Understanding the Pros and Cons of Different MERV Rated Air Filters

When it comes to air quality, the Minimum Efficiency Reporting Value (MERV) rating of an air filter is an important factor to consider. MERV ratings range from 1 to 16, and filters with higher MERV ratings trap small particles more effectively than filters with lower MERV ratings. However, using a filter with a high MERV rating can also mean that the HVAC system must work harder to move air, resulting in a reduction in energy efficiency, an increase in utility bills, and a decrease in the longevity of your HVAC equipment. The MERV scale is not linear; the difference between a MERV 6 and a MERV 8 is almost double in the percentage of particles captured.

Keep in mind that as the MERV rating increases, the filter becomes more restrictive and more pressure and energy will be needed to expel air. If chemical disinfectants are used, they should only be applied with the air conditioning system turned off. In addition, disinfectants should not be applied to ventilation filters before continuing to use filters within ventilation systems. The effects of disinfectants on filter performance are unknown.

Filters should only be treated with disinfectants if they are going to be removed from service and discarded. While UV systems are quite effective at maintaining the cleanliness of HVAC coils, drain trays, and other damp surfaces, properly designed systems can be very effective at inactivating microorganisms in moving air currents on the fly. These systems generally require more lamps so that they can provide significant doses of UV in a short period of time. A typical single-pass inactivation efficiency is 85%, much like that of a good particulate filter, but systems can also be designed for inactivation greater than 99.9%.

In addition, a well-designed UV air disinfection system within an HVAC system and located next to the cooling coils can also provide the surface disinfecting benefits mentioned above. Another way to install UV is in an “aerial” configuration. Specially designed wall-mounted accessories create an irradiated area above the occupant and disinfect the air in the space as the air circulates naturally, mechanically or through the HVAC system. The CDC has approved this type of system for use in TB control for nearly 20 years, and there is guidance from the NIOSH on how to design them.

Finally, mobile UV systems are frequently used for cleaning terminals and disinfecting surfaces in health centers and other spaces. Systems like these are normally used in unoccupied spaces due to concerns about occupant exposure. All three types of systems may be relevant, depending on the type of building and the individual spaces within the building. Designing and sizing effective ultraviolet disinfection systems can be a complex process due to the need to determine the dose administered to a moving air stream or to an irradiated region of a room.

Inlet systems are further complicated by the configuration of the air handling unit and ducts and reflections from surfaces, which can help achieve higher irradiance levels. Superior air systems require an adequate air mix to function properly, while paying close attention to reflective surfaces that could cause room occupants to be overexposed to UV energy. Accredited manufacturers and system designers can help by making the necessary calculations and designing specific systems for individual spaces. To better understand the best type of HVAC air filter for your home, you'll need to understand the different types of air filter technology, as well as the pros and cons of each type.

Washable air filters tend to have a lower MERV rating and are less efficient, while a high-quality disposable filter might better filter the air. For a residential filter with a slightly loose groove, you can use a simple piece of adhesive tape, hold it in place, and allow the air flow to push the filter forward so that it comes into contact with the flat surface in front of it. At an inclination of 45 degrees, each filter has approximately 1.4 times the area of a filter that covers the same half of the duct horizontally or with an inclination of 0. HVAC unit technology has progressed since then, and most modern units in recent years should be able to have at least one MERV 8 filter.

Air filters with MERV 13 or higher are recommended for those who prioritize air quality and may need to treat allergies or asthma symptoms. Some technicians anticipate that people will forget to change their filters, and the regular use of low-efficiency filters could help minimize damage to a neglected heating, ventilation, and air conditioning system. In fact, an HVAC filter cannot be considered a HEPA filter unless it consistently filters at least 99.97 percent of all particles that are 0.3 microns or larger. Thanks to this site and the trails I took, I have learned that two MERV 11 filters can have the same filtering capacity but one could allow more air to be transferred.

With more than 57,000 members from more than 130 countries, ASHRAE is a diverse organization dedicated to promoting the arts and sciences of heating, ventilation, air conditioning, and refrigeration to serve humanity and promote a sustainable world. As you can see above, research shows that in general HVAC systems with filters that are high in MERV have a greater pressure drop across the filter. A well-known company demonstrated their MERV 13 filter compared to others based on this information. To sum up: when selecting an HVAC air filter for your home or business it is essential to consider both its MERV rating as well as its ability to allow adequate airflow through your system without causing too much strain on your HVAC equipment.