How Often Should You Change Your Furnace Filter? And other Furnace Filter FAQs Answered!

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How Often Should You Change Your Furnace Filter? And other Furnace Filter FAQs Answered!

As the saying often goes, “out of sight, out of mind” – and that’s probably the attitude most people take towards their furnace filter. So long as you’re keeping warm in the winter and cool in the summer, then you’re not paying any attention to it. And that’s totally fine – but take a moment to think about when you last replaced your furnace filter.  If you can’t remember, then it’s probably time to take action. 

Your furnace filter is a powerhouse tool in your HVAC unit – protecting it from all the dust and debris that circulates throughout your home. Additionally, its work protecting your unit also helps to purify the air in your home, so replacing your filter is a key element in the overall care of your HVAC system and the health of your family. 

If you have central heating, ventilation, and air conditioning system then you can use the terms “air filter” and “furnace filter” interchangeably when referring to its components.  

Here are some of our customers’ most frequently asked questions about the care and upkeep of their air quality, furnace, or filter. 


 1. How Often Should You Change Your Furnace Filter?

To answer this question honestly entirely depends on the type of furnace filter in place. Typically, the filter’s manufacturer provides the recommended replacement frequency within the product information when you buy a new filter. 

Beyond the manufacturer’s recommendation, the size of the furnace filter also impacts the frequency in which the filter requires changing. Thicker filters have more media available to capture containments, so a 5-inch filter requires less frequent changes than a 1-inch filter. Our standard recommendation is as follows: 

  • For 1- to 2- inch filters, replace them every 1 to 3 months. 
  • For 3- to 4- inch filters, replace them every 6 to 9 months. 
  • For 5- to 6- inch filters, replace them every 9 to 12 months. 

At Crystal Heating and Cooling, we also provide an Air Filter program – where we eliminate the need to worry about when you last changed your filter. When you subscribe to our program, we will deliver the right filter for your system straight to your doorstep at the recommended time. 


2. What happens if you don’t change your furnace filter?

Furnace filters play a vital role in your home’s HVAC system and indoor air quality.  When a dirty air filter is in place, there is a large risk of compromising your comfort, energy costs, and your HVAC system.  This is because your HVAC system will work harder and more frequently with a dirty filter. There are also a number of safety concerns when you don’t routinely change your air filter, including clogging, overheating, fire, and short cycling (which causes your furnace to turn off). 

The main purpose of a furnace filter is to trap airborne contaminants – such as dust, debris, hair, and other pollutants – and keep them out of your heating and cooling system. This also aids in the indoor air quality of your home. 


3. How do I know if my furnace filter needs to be replaced?

Although seemingly small in stature and strength, your furnace filter plays a crucial role in the overall functionality of your HVAC system. Replacing the filter is often the first step in HVAC troubleshooting. Signs that your furnace filter needs to be replaced can look like any of the below: 

  • An increase in your heating/cooling bills 
  • You’re noticing a funny smell 
  • Your furnace is running for longer times, but there is less heat 
  • You’re noticing more dust, debris, and hair floating about 

If you find yourself wondering about any of the above – take a look at the filter! If it is a grey colour, and covered in dust and lint, then it is definitely time to be replaced. 


4. What happens if you put a furnace filter in backward?

Replacing the air filter is not a difficult job as most will have an arrow on the cardboard sides of the filter. This arrow must point toward the furnace, away from the return duct. If you are able to remember, try to take note of the direction of the filter before removing it. It can also help to draw the airflow direction on the furnace with a permanent marker as a helpful reminder. You can also label your new filter with the replacement date in case you forget the last time you replaced your furnace filter. 

Installing a furnace filter in the wrong direction can subject your HVAC unit to unnecessary wear. Incorrectly installed air filters will collect more dust and debris, which forces your unit to work harder to heat and cool your home. 


Ultimately, if you cannot remember when you last changed your air filter – then it’s time to take action. Sign up for our Air Filter program, or call us for assistance! If you have already changed your air filter and are still experiencing heat loss, increased energy bills, and longer run times – then give us a call at 519-756-6888. We provide 24/7 service whenever you need us.