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  • Writer's pictureRob Mitchell

HVAC System filter types

Updated: Jan 9

Furnace Filter Types

Every HVAC system has an air filter. This filter traps unwanted allergens and debris from the air in your home. Choose the right type of filter to improve the efficiency of your HVAC system. Following are the most common types of filters that you can use for your system.

Fiberglass/Synthetic Filters

Fiberglass or synthetic filters are a cheap and disposable option for your furnace. They catch up to 80% of particles 50 microns and larger and 25% of particles between 3 to 10 microns. Considered minimum protection, fiberglass/synthetic filters prevent dust and dirt from building up on heat exchangers, fan motors, and other surfaces. The larger particles are trapped and eliminated, so your furnace components remain clean. They allow your system to have maximum airflow but don’t filter harmful contaminants affecting your health.

Polyester Filters

Polyester filters come in medium sizes and are made of high-quality materials. They trap and eliminate 80% to 95% of particles 5 microns or larger. A polyester filter costs four times more than the average fiberglass/synthetic filter, but it offers more protection against pollutants that may cause health problems.

Pleated Filters

The most popular type of HVAC filter is a pleated filter. These are both affordable and effective filters. A pleated filter offers high-efficiency results by trapping particles down to 0.3 microns in size, such as bacteria and viruses. Pleated filters are more efficient and last longer compared to fiberglass/synthetic filters. They eliminate more pollutants from your air without sacrificing airflow within your system.

Washable Filters

Washable HVAC air filter types are available in flat paneled and pleated forms. They cost more than disposable filters but will save money in the long run. Also, they are more environmentally friendly than their disposable counterparts.

To clean these filters, you need to vacuum or rinse them to remove any dirt and impurities. It is critical to ensure that the filters are fully dry before reinstalling them. Using damp filters can lead to mold and mildew developing on the filter and being expelled into the air you breathe.

Electrostatic Filters

Using small cotton and paper fibers, electrostatic filters create static that acts as a magnet for dust and other airborne particles. This makes them one of the best choices for those who need a filter that can combat allergens. The magnetism is strong enough that it keeps these particles from spreading throughout your home. While this filter does a good job filtering smaller pollutants, it does not do well with larger ones, such as dust or mold spores.

HEPA Filters

High efficiency particulate air, or HEPA, filters provide high-end filtration by trapping up to 99% of particles 0.3 microns or larger. Even though they are excellent at eliminating indoor pollutants and create a healthier environment in your home, they can drastically reduce your system’s airflow, costing more money in energy usage.

UV Filters

UV filters/ UV lights use short-wave ultraviolet light to kill bacteria and viruses. When air passes through the HVAC unit, the UV lights will disinfect it with radiation. UV filters are excellent for killing microorganisms that could be hazardous to your health. These lightbulbs generally need to be replaced every year. UV filters are used in combination with other filter options. UV filters don't remove dust and other pollutants from your system.

Furnace Air Filter Ratings

In addition to their type, most furnace air filters have a MERV (minimum efficiency reporting valve) rating. The higher the number, the more efficient it is at removing contaminants from your air.

Though MERV ranges from 1 to 20, the ideal range for a home is from 8 to 13. If you go too low, you won’t be able to capture particles and clean the air. Too high, and you’ll force your heating and cooling system to work too hard filtering everything. Too much of this, and your HVAC won't last as long as it should.

MERV 1-4

These filters offer a minimum amount of protection as they are primarily designed to assist the cleanliness of the HVAC units by filtering out particles that can damage the coils and harm the efficiency of the unit. They remove pollen, dust mites, and other harmful fibers. With <20% dust spot efficiency, these filters are the best option where budget is a concern and health issues are minimal.

MERV 5-8

These filters are a step up from the MERV 1-4 air filters. Here, the air filter is able to also remove mold spores and dust from the air. These filters have a 20-35% dust spot efficiency and offer higher air filtration than lower rated filters while remaining budget friendly.

MERV 9-12

These filters catch the smaller particles such as those known to cause allergies. A MERV 9-12 filter will remove pet dander, auto emissions and other smaller airborne particles from the air, creating a cleaner air supply. This is a great choice for those who have mild to moderate allergies or other respiratory ailments.

MERV 13-16

These filters are the highest quality home filters available other than HEPA filters, making them good for those who are often afflicted by allergies and respiratory issues. The filters in this range are the ultimate protection against dust, pollen, mold, bacteria, viruses and the smaller airborne particles that often make breathing difficult for people with advanced sensitivities to poor air quality or weakened immune systems.

However, a higher MERV rating on a filter doesn’t necessarily mean that it is the best option for your furnace. In fact, as MERV rating goes up, air flow goes down—forcing your HVAC system to work harder to push air through your furnace, increasing the possibility of a potential breakdown. Before purchasing a new furnace filter, you might check your furnace manual for a recommended air filter MERV rating. If it has one, be sure to buy a furnace filter with a MERV rating below your system’s maximum.

Make sure you are looking at a MERV rating for comparison. Some big box retailers use a filter performance rating (FPR), which ranges from 1-10. Occasionally, you might also see the microparticle performance rating (MPR) system, which goes from 300 to 2200 and measures a filter’s effectiveness at trapping only the smallest particles on the MERV scale (0.3-1 microns in size).

Sizes of Air Filters

Air filters come in many different sizes. It is important that you select a replacement air filter that fits your unit’s filter cabinet correctly. The easiest way to determine the correct size is to measure your current filter. You will probably need to remove it to measure it. Make sure you note the direction of the airflow arrow on the filter's frame before removing it. Having the correct height, width and thickness are all important. Once you have determined the correct filter size, you may find it helpful to write the dimensions on the front of the air handler for future reference.

Should you need more assistance selecting your air filter, let us know. We will be happy to help.

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