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What Type of Air Filter Should I Use? 

Removing Air Filter

Removing Air Filter


Changing your air filters on a regular schedule is important for the life expectancy of your unit and key in providing clean air to your home or business. We suggest changing them at least every 3 months but there is another consideration to make. What type of replacement filter best serves your needs? Choosing the right kind of filter requires both the correct size and the correct type for your system.

A lot of homeowners have been lead to believe that air filters are mainly for air quality. While it is true that air filters affect air quality, primarily, the purpose of the filter is to protect the HVAC equipment. And actually, having an air filter that is “high efficiency” cause issues with airflow, which can freeze the condensing coils on an AC unit. Furnaces can also suffer from slow airflow caused by filters that are “too good” – meaning that the filters are so fine that they actually slow air flow beyond what the system needs to operate. Slow air flow over the heat exchangers will reduce the efficiency of the unit, raise energy bills and cause damage due to overheating with the furnace.

A dirty filter can have the same effect.

Another reason that air filters are only partially about the quality of air is that they don’t run constantly. So contaminants in the air can only be trapped when the system is in operation and the fans are running. What type does your system need? If you have questions, give us a call. Here is a quick primer on the different kinds you may come across.

Fiberglass HVAC Filters

These filters will keep hair and large dust particles from settling on and causing damage to HVAC components. They allow maximum airflow, but are really just a barrier for the system components. Don’t expect them to have much impact on air quality. If you don’t have any pets, allergies or chronic respiratory issues, these may be the right fit. They are the least expensive and are intended to be disposable.

Pleated HVAC Filters

These are a step up in how fine the screen pores are and trap the majority of airborne pollen, pet dander, and dust mites as small as 5 microns. You’ll find these in use widely across the country and you can tell them apart from fiberglass HVAC filters by their V-shaped chevron pattern. If you’re concerned about allergens or pet dandruff, making the step up to these for your home or office is a good choice.

Electrostatic HVAC Filters

Manufactured with a self-charging fiber that attracts particles like an electrostatic mop, this style of filter allows good air flow while being very effective in trapping particles. Particles measuring as small as 1 to 3 microns get trapped in this style. Since these work not by needing fine pore size, but by electrostatic action, they are able to give better filtration without sacrificing air flow.

There is also a MERV ( Minimum Efficiency Reporting Value ) with all air filters, so be mindful that even though a filter may be electrostatic in action, the MERV rating is the true measure of how well it filters.

Table grouping MERV ratings by particle size: 




These style of filters have another benefit in that they also come in reusable, washable versions. They cost the most up front, but over their lifetime, they give the best filtration, air flow and return on investment.

HEPA Filters

High-efficiency particulate air  (HEPA) filters are the most efficient available – in terms of what they are able to trap. At MERV 17 to 20, these filters are capable of trapping 95 percent or more of mold, fine dust, asbestos, bacteria, and viruses measuring as small as 0.3 microns. However, your HVAC system may need to be modified to allow them to run correctly. Their action is due to extremely dense and fine pores, and this restricts airflow. Restricted airflow causes the problems we discussed in the beginning. Their expected usage is if you or a family member has severe allergies, asthma or chronic obstructive pulmonary disease (COPD).