Guide to Furnace Filter Change Frequency

Furnace filters don’t last forever, and knowing the right time to replace them can make a big difference in the comfort of your home, as well as save you money on the operating costs of your HVAC system. Of course, furnace filters are not something most people think about all the time (but we do!). It’s one of those ‘out of sight, out of mind’ things that can unfortunately get forgotten, which eventually leads to poor air quality in your home and can decrease the energy efficiency of your furnace. It could even cause furnace components to wear out faster, resulting in unexpected faults or breakdowns.

Staying on track with regular furnace filter changes can be as easy as setting a recurring reminder on your smartphone calendar, or putting a date reminder in a highly visible area of your home. But how exactly do you know what the right interval for furnace filter changes needs to be for your home? Well, that’s why we’re here! We’ve taken the time to pull together everything you need to know about the optimum time to change your furnace filters, and why there might be some instances where you’d need to change it sooner. Let’s get started!

How Often Should I Replace My Furnace Filter?

It sure would be nice if there was a neat and tidy formula that told you the precise day to change your furnace filter, but in the real world, it doesn’t happen exactly like that. That said, there are some general guidelines to follow that will work well for the majority of Canadians and give them a great balance of air quality, and energy efficiency, and filter longevity. The most common furnace filter change interval for homes in Canada is once every 2-3 months, or about four times a year.

As you may have guessed, this interval more or less coincides with the cycle of the seasons, which makes a lot of sense when you think about how environmental conditions change the way we manage the comfort of our homes. During the hot, humid months of the summer, it’s common for windows to remain closed as AC units cool our living spaces down. In the winter, furnaces run regularly to keep us warm and comfortable. On the milder days of spring and fall, it’s nice to be able to open the windows and get some natural airflow through the home. However, it’s still important to continue to filter the air in the home by recirculating it through the HVAC system, even if the heating and cooling settings are temporarily paused.

Why Would I Need to Change It More Often?

Like we said, that 2-3 month interval is a general benchmark for furnace filter changes, but there are many other factors that can influence how frequently you should change the furnace filter in your own home. Let’s explore some of the most common things that might make your filter dirtier faster.

More People Living in the Home – This might seem obvious, but simply having more people living in the home will increase the amount of dust and dirt that is inside and stirred up into the air. For homes that experience a lot of traffic with 4+ people living there, you will likely find that your furnace filter gets loaded up at a much faster rate than those homes with just one or two people.

Pets – Cats and dogs produce a lot of hair, that’s for sure. The fur they shed ends up all over the place, getting pulled into return air vents to be captured and contained in the furnace filter. This definitely will increase the recommended frequency of filter changes. Increasing the frequency of vacuuming might help alleviate the amount of pet hair and dander that’s in the air a bit, but it certainly can’t catch it all.

Environmental Conditions – Depending on where you live in Canada, there can also be environmental differences that will affect how often you’ll need to change your furnace filters. Areas with drier climates will inevitably be dustier than areas which experience more rainfall. Homes located in rural communities will also have higher volumes of airborne pollen and dust to manage than those in larger cities due the lower number of plants and trees found in developed urban locations. Aside from geographical factors, climate cycles can also increase or decrease the amount of dust and pollen in the air as seasons change. A year where the rainfall is heavier than usual might not generate as much airborne dust compared to years where things are drier.

Allergy Control – If you or someone who lives in your home suffers from seasonal allergies, or has any kind of respiratory sensitivity to airborne particles, increasing the frequency of furnace filter changes can help reduce the symptoms they experience. Filtering the air inside the home while it is continually recirculating helps capture and contain a greater volume of dust, pollen, and pet dander particles that are common irritants for people with allergies. However, constant recirculation can cause the filters to load up at a faster rate, necessitating more frequent replacements to maintain proper filtration performance.

Home Renovations – Most people might not think of a home improvement project as a primary reason to change a furnace filter, but the amount of dust and airborne particles that get stirred up during renovations would really surprise you. Aside from the obvious things like sawdust and drywall dust that are common during home renovations, built-up dust and pet dander hidden in carpets, in between floorboards, and around furniture can quickly become airborne. Be sure to check the filter regularly throughout the project to monitor how dirty it is. If it’s clearly full of dust, definitely replace it. If you’re not sure just how dirty it is, it might be a good idea to replace it anyway, and you’re absolutely going to want to install a fresh one after the renovations are completed.

Do Some Filters Last Longer Than Others?

You might be curious if there’s such a thing as ‘long life’ furnace filters. The answer is ‘sort of’. The duration of useful life for a furnace filter is clearly influenced by all the factors we just discussed, but there’s one more aspect to consider. This physical depth/thickness of the filter also contributes to how long it will last before it should be replaced. The deeper the filter, the more it can be loaded, which refers to its ability to hold captured dust and airborne particles.

Most residential home furnaces use a 1” depth furnace filter, however there are several makes and models of furnaces that utilize thicker filters. The other common furnace filter sizes include 2”, 4”, and 5” thick styles. 1” and 2” filters usually follow the 2-3 month change interval, however 4” and 5” thick filters may be specified to last as many as 4-6 months before needing a change. Of course, this also depends on all the other factors we talked about that can increase the filter change frequency.

Ultimately, if the current filter looks extremely dark and dirty compared to a fresh filter, then it’s a really good idea to give it a change, regardless of how many months have passed. It’s always better to change furnace filters more often than less often, as the quality of the air in your home depends on having a furnace filter of adequate filtration performance and capacity.

How Do You Change a Furnace Filter?

Changing a furnace filter is quite simple, and often requires no tools of any kind to complete the replacement procedure. Here’s the step-by-step of how to swap out your old furnace filter for a fresh one:

1. Make sure the furnace and AC unit are switched entirely off before you proceed. They should not be operating in any way during the filter change process.
2. Locate the furnace filter tray/slot, which is usually located near the base of the furnace where the intake ductwork connects to the main furnace assembly.
3. Remove the filter from the furnace by sliding it out towards you. Sometimes the filter will be held in place by a clip or retaining screw, so you may need to remove this first before gaining direct access to the filter itself.
4. Orient the new filter in the same way as the old filter. However, it’s always wise to double check this to make sure the airflow indicator printed on the filter itself matches the direction of the airflow in the ductwork. Furnace filters are always located in the system BEFORE the air in the ducts enters the main furnace assembly, so the arrow printed on the filter casing should always be pointed TOWARDS the furnace.
5. Ensure the filter is situated completely inside the filter slot and not protruding out the side of the ductwork. If it does, you may need to resituate the filter, or it’s possible that the filter is too big for this particular furnace. Refer to our filter sizing guide for complete details on how to choose the correct size of filter.
6. Replace the filter holding clip or retaining screw, if applicable. Your replacement furnace filter is now installed, and you are ready to switch the furnace or AC system back on. Well done!
7. Dispose of the old furnace filter by placing it inside a large plastic bag to contain any dust or dirt from being shaken out of it when it is carried out of your home. It can then be safely disposed of as part of your regular household garbage.

What If I Have Other Questions About Furnace Filters?

We’re here to help! We have many handy resources you can check out to learn more about filter sizing, specifications, energy savings, air quality, and more. Visit our Filter Facts blog to see the latest helpful articles, and don’t hesitate to get in touch with us. We’ll be glad to answer any questions you might have!