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Common Types of HVAC Filters

 

Trying to find the best air filter for your indoor space can be a daunting task, especially with all the different types available. Different HVAC filters cater to different space sizes, types of occupancy and most importantly the type of air quality required. 

Understanding the different air filter types for your space is the first step to improving and managing indoor air quality.

There are five commonly used HVAC air filters:

  1. Pleated Media Filters
  2. Fiberglass Air Filters
  3. Electrostatic Filters
  4. UV-C Supplemental Air Sanitization
  5. HEPA HVAC Filters

 

What is a MERV rating?

Before we get into detail about the types of filters, it's important to understand what a MERV rating is, and how it applies to air filters. MERV ratings or Minimum Efficiency Reporting Value is a measurement system created by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) to signify an air filter’s effectiveness. The higher a filter’s MERV rating, the more effective it is at capturing smaller airborne particles.

Fibre-Glass Air Filters

Fibreglass filters are a type of non-pleated filter, alongside electronic and electrostatic air filters. Non-pleated air filters, also known as disposable filters, are less expensive and most effective for large particles, such as lint, dust and even insects.

Non-pleated air filters are not designed to last very long. However, you can choose to buy metal-reinforced fibreglass filters for extra rigidity. Their MERV rating is between 1 and 4 (low). Their main purpose is to protect your HVAC unit from large dust particles; however, they do not trap mould, pollen, or other small particles and are not recommended for homes with people with allergies.

One of the biggest benefits of buying non-pleated filters is that they fit any type and model of HVAC system and are quite inexpensive.

Advantages:
  • When compared to pleated filters, or other more effective options for air filtration, the fibre-glass filters are relatively cheaper. 
  • Fit in any type and model of an HVAC system.
Disadvantages:
  • Not effective at removing small particles.
  • Fibre-glass clogs up relatively fast and as a result, it must be changed more often or your air handler will have to work extremely hard and use a lot of energy to compensate.

Pleated Media Filters

Pleated filters have a fabric medium commonly made of polyester or cotton and are designed so that the surface area increases and is able to hold large amounts of sediments, whilst minimizing the reduction in airflow. As a result, pleated filters are more efficient than non-pleated filters at capturing microscopic airborne particles. Pleated filters can successfully filter:

  • Dust mites
  • Dust
  • Pollen
  • Mould
  • Pet dander
  • Other smaller bacterias
Advantages:
  • The pleats in these filters give them an advantage over non-pleated options because they increase the filter’s surface area for better filtering. 
  • Pleated filters are available in multiple MERV ratings, ranging from MERV 5 and 13.
Disadvantages:
  • The downside to pleated filters is that they require your HVAC system to work a little harder to pull air through the unit; this may result in your HVAC system losing pressure.

Electrostatic Filters

An electrostatic filter induces an electrostatic charge to any and all particulates that pass through the air cleaner. This allows pathogens to be easily removed from the air with oppositely charged fibre media that act like magnets.

Electrostatic polarized filters, in particular, are a type of electrostatic filter and perform exceptionally well in removing sub-micron particles less than 1 micron in size. Let’s take the example of a magnet, polarized technology works similarly to how magnets' positive and negative sides attract each other.

Polarization is the process of inducing an electrostatic charge to any and all particulates that pass through the air cleaner. This allows pathogens to be easily removed from the air with oppositely charged fibre media that act like magnets. The charged polarized particles attach with other polarized particles as they collide in the air, creating a “polarized field”. This field binds the submicron particles, allowing the air cleaner to capture even the smallest particles.

Advantages:
  • Most electrostatic polarized filters can capture particles 40x smaller than standard filters.
  • Unlike electrostatic ionizing filter technology, polarized filters do not emit ozone.
Disadvantages:
  • Best suited for large commercial spaces. Electrostatic polarized filters are the best option in HVAC systems and buildings where enhanced air quality is required but a HEPA filter is not practical.

UVC Supplemental Air Sanitization

Ultraviolet radiation is a type of electromagnetic radiation that carries a short wavelength and a higher level of energy. UVC light is the type of UV light that’s most effective at killing germs. It can be used to disinfect surfaces, air, and liquids.

Specifically, UV-C is effective at killing fungi, bacteria, germs, viruses, and other pathogens. For this reason, UV lights have common applications in sterilizing hospitals, water, germicidal lamps in food establishments, and HVAC systems. UV-C has demonstrated the ability to effectively and safely inactivate the SARS-CoV-2 virus up to 99.9%.

Advantages:
  • The ultraviolet radiation used in these filters is strong and can destroy tough microorganisms such as viruses, bacteria, mould, and yeast.
  • There is no added static pressure to existing HVAC systems.
Disadvantages:
  • UV-C does come at a greater cost than most other filters, but the good news is, that this level of filtration is not required in most buildings.

HEPA Filters

High-efficiency particulate air filters are recommended by the Centers of Diseases Control and Prevention and are able to remove up to 99.97% of the air-borne pollutants and allergens present in your home, including dust, mould, pollen, pet dander, viruses, smoke particles, and bacteria. As a result, those who live with allergies or other respiratory issues truly benefit from HEPA filters.

These filters do need to be adjusted by a contractor to fit your specific HVAC system.

Advantages:
  • Helps to remove large and small air-borne pollutants and allergens present in your home.
  • Most HEPA filters only need to be replaced every few years, making them very cost-effective.
Disadvantages:
  • Smaller particles like smoke, fumes, or gasses can still pass through the filter.
  • Their high filtering ability might restrict airflow, causing your HVAC system’s efficiency to drop.