Furnace Filters 101 Everything You need to know


When was the last time you changed your furnace filter? Hopefully, it’s been within the last six months. Unfortunately, many homeowners let their filters go unchanged for too long.  Let’s talk about how, why and when to change your furnace filter and discuss why should you change your filter, when is it time to change your filter, how to change your filter, and finally, what are the next steps.

What is the Purpose of a Furnace Filter

A furnace filter is used to catch debris in the air and prevent it from being recirculated around your house. As your system runs and collects the debris floating in the air, eventually a new furnace filter is needed. If a furnace’s filter is changed on a regular basis, dirt will continue to collect, ultimately restricting air flow. Restricting air flow has a number of negative effects, such as pockets of hot and cold spots in your home, lack of air flow to certain vents, longer run times for your furnace or air conditioner, higher bills as a result of the longer run times, and less comfort in your home. These negative effects may seem small at first, but can lead to larger problems the longer the furnace filter is neglected. In fact, a furnace is capable of running for months or even years with a clogged filter. Running with a dirty filter for too long will be more costly, less comfortable, cause your system to break down prematurely, or stop working altogether, all because of a filter. Moral of the story? Change your filter on time.

When you should change your Furnace Filter

Each filter comes with a recommended replacement schedule printed on its packaging. Some are as early as 30 days while others need to be changed once a year. Whatever your replacement interval is, it’s recommended that you stick to it. Some homeowners may need to change their filters more frequently in order to keep their HVAC system running. For example, if you have multiple pets, their hair and dander may cause your filter to clog more quickly. During allergy season, the increase in pollen in the air may cause your filter to clog quicker. If you are in a smoking household, filters will collect particulates from this more quickly than some other homes. Lastly, the frequency your system runs will also increase the use of your filter. If you’re running the system almost constantly in a particular system, timely replacements are of course recommended. Additionally, if you start noticing unusual odors or more dust than usual in your home, it might be a sign that your furnace filter needs to be cleaned or replaced. 

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How to Change your Furnace Filter

Regardless of the type of filter you have, the steps should apply. First, safety should always be a priority when you do any maintenance on your HVAC system. You do not want it kicking on while you’re doing any work. The easiest way is to turn off the furnace at your circuit breaker. Next, locate where your filter is. Filters are always located between the air return duct and the supply duct. Depending on your system, the filter can be located on the side, underneath, or inside the unit itself. Third, identify the direction of the air flow. Remember that the air flows from the return air duct into the furnace before it’s conditioned and recirculated to the rest of the house. It’s important to have the furnace filter pointing in the right direction when you replace it to not restrict air flow. Remove the old filter. It should easily slide out.

Once removed, slide the new filter in, making sure the orientation and the arrow on the new filter points in the direction the air is moving. Keep in mind that the furnace filter may catch on some rough edges as you remove or slide in the new filter. If this happens, take your time and wiggle the filter around until it becomes free from any snag. If your system uses a media filter, make sure to line the filter with the tracks inside the casing. If your setup is complicated in a tight, hard to reach space or if you’re unsure of how to change your filter, let us know. We’re happy to help look at the new filter and make any changes necessary during your next maintenance visit.

It should be noted that some HVAC systems use washable filters. These semi-permanent air filters last a long time as long as you wash them on a regular basis. However, if you don’t want to hassle with washing them, you can consider replacing them with a paper or fiberglass filter. I hope by now you have a better understanding of the importance of changing your furnace filter and the tools and confidence to be able to do it yourself.