We may not think about it often, but the air we breathe is essential to our health and wellbeing. Air filtration is an effective way to trap airborne pollutants — and choosing the right filter is the first step to clean and healthy air. (Air filters are also important to maintaining your furnace and AC.) There are many kinds of furnace filters to choose from, so this guide will help you find the right one for your needs.
Air Filter Terms to Know
Depending on where you live, you may find furnace filters, air filters, AC filters or HVAC filters in your local home or hardware stores. Filter manufacturers use these terms interchangeably, but they all describe the same thing. If you live in a colder climate like Canada, the term furnace filter may be more common than AC filter.
Aside from using different terms for their filters, manufacturers have also created different rating systems to measure their efficiency:
- MERV (Minimum Efficiency Reporting Value) ratings range from 1 to 16. The default rating is MERV 8, which will remove most contaminants and viruses, while the highest rating can trap microscopic pollutants as small as 0.3 microns. You may want a filter with a higher MERV rating if you’re looking to remove asthma/allergy triggers such as pet fur or dander.
- MPR (Microparticle Performance Rating) includes microscopic particles not measured on the MERV scale. The MPR range measures particles between 0.3 and 1 micron in size, which is a lot smaller than common dust and pollen particles.
- FPR (Filter Performance Rating) is similar to MERV but uses a scale from 4 to 10 with a corresponding colour-coded ranking. From green to red to purple to black, the colours indicate the filter’s ability to remove particles from the air. The highest rating (black) can remove large and small particles as well as odours.
- HEPA (High-Efficiency Particulate Air) filters correspond to MERV 16 and remove up to 99.97% of airborne allergens and pollutants. HEPA filters require professional adjustment and are the most expensive option, but provide the most efficient air filtration for people with air conditioner allergies or respiratory problems.
Types of Furnace Air Filters
There are many different types of furnace air filters, each with their pros and cons.
One of the most common air filters, these filters consist of spun fibreglass that is reinforced by a metal grate. They are disposable, affordable and won’t affect the airflow in your HVAC system. However, fibreglass filters are not very effective in removing harmful pollutants, viruses and allergens from the air: while they will catch 80% of large particles, only about 25% of smaller particles (3 to 10 microns in size) are cleaned from the air circulating through your home.
|Low cost Debris, lint and dust removal
|Ineffective in removing smaller particles Easily clog Frequent replacement required
Consisting of polyester or cotton, the pleats and folds in these filters increase the surface area to capture as many particles as possible. Slightly more expensive than fibreglass filters, they are very effective in filtering small air pollutants such as pollen, pet dander and mould spores.
|Effective air filtration Long-lasting Reusable and disposable formats Noise reduction of the furnace fan
Electrostatic filters create an electric charge that acts like a magnet, attracting and trapping pollutants from the air. Depending on your furnace, electrostatic filters may be disposable or washable. With a MERV rating between 4 and 10, they help remove microparticles from the air and are ideal for people with allergies or respiratory issues.
|Low cost Reusable options eliminate replacement costs Effective air filtration of small particles
|Not as effective in removing larger particles such as mould spores and dust
Activated Carbon Filter
Activated carbon filters are used in air purifiers to remove odours, smoke, gases and volatile organic compounds (VOCs) from the air. These filters work by adsorption (which is different than absorption), a filtration process where the particles stick to the carbon inside the filter and are removed from the air.
|Removes gases, vapours, odours and VOCs Improves air quality Low cost Long-lasting
|Not effective in removing allergens, bacteria or viruses Not effective in trapping fine particulate matter
Ultraviolet (UV) filters disinfect the air passing through them, using the radiation of short-wave UV light to eliminate microbes, bacteria and viruses. This makes them a great option for people with compromised immune systems. However, they are not very effective in removing dust and other air pollutants, so they are usually installed in combination with another filtration system.
|Remove microbes, bacteria, viruses and other harmful micro-organisms (e.g., mould spores)
|Ineffective for removing pollutants and allergens Higher cost Can emit ozone, which could worsen asthma or other respiratory diseases
Polyester filters are very effective in removing harmful particles from the air, cleaning and removing up to 95% of contaminants that are 5 microns in size or larger. Made of high-quality materials, these filters are more expensive than fibreglass or synthetic filters but offer better protection and health benefits.
|Effective air filtration
Reusable and Washable Filter
Both flat-panelled and pleated filters can be purchased as a reusable or washable option. While they cost more upfront, they will be cheaper in the long run as you won’t need to purchase as many replacement filters. (This also makes them the more environmentally friendly option.) The filters wash easily with soapy water or a damp cloth, but must dry completely before they’re reinstalled to avoid mould and bacteria buildup within your HVAC system.
|Low cost Environmentally friendly
|Regular maintenance is required Not efficient in removing odours
One of the most efficient filters on the market, HEPA filters remove up to 99.97% of pollutants and allergens, including dust, mould, pollen pet dander, viruses, smoke and bacteria. More expensive than fibreglass and pleated filters, HEPA filters provide optimal air quality — important for people with allergies or respiratory illnesses.
|Effective against both large and small pollutant particles Filters need less frequent replacement, making them cost-effective in the long run
|May restrict the airflow of the HVAC system Higher upfront cost
7 Factors to Consider When Choosing a Type of Furnace Air Filter
Before selecting an air filter, it is important to check the manual of your HVAC system to find out which type of filter it requires. The following factors should be considered when choosing your air filter:
The size of air filters typically refers to their thickness (or depth) as well as their height and length. Air filter thickness usually ranges between 1 and 5 inches. Overall filter sizes can vary from 10 to 30 inches in height and length. To find out which size your system requires, you can either check the owner’s manual or look at the existing filter to make sure the new filter will fit. It’s important to purchase the correct size to ensure your system will run properly.
For residential homes, a MERV rating between 8 and 12 is usually sufficient. Filters with higher MERV ratings may actually overextend or block air flow and cause service issues with the furnace because they’re usually used in non-residential settings such as hospitals or laboratories.
Indoor Air Quality
The air quality in your home may be affected by pets producing dander, people smoking, wood-burning fireplaces or gasses emanating from your stove. When choosing a filter, you should take into account the specific needs of your household.
Climate and Outdoor Air Quality
Air quality is also affected by what happens outside of your home. If the air quality in your area is poor, you’ll want to consider filters with a higher efficiency rating and a larger surface area to remove the harmful pollutants.
If there are people in your home with allergies, asthma or respiratory problems, choose the highest-rated filter suitable for your HVAC system. Just keep in mind that while a HEPA air filter may provide additional benefits, it costs more and may require new equipment.
Cost varies significantly between the different types of air filters but most disposable filters need to be replaced after 30 to 90 days. To avoid this recurring cost, you may want to choose a washable filter that can be reused for up to 10 years. While they will cost more upfront than disposable filters, washable filters avoid waste and provide cost savings in the long run.
Ask Enercare’s Experts for Help
With the many different types, ratings and sizes available, purchasing a furnace air filter can be confusing. Always consult the operating manual to know the technical requirements of your HVAC system — and contact our team of experts if you have any questions about selecting the right furnace air filter for your home.