Furnace Filter Guide: Everything You Need to Know

Your furnace air filter, also known as the HVAC air filter, plays a critical role in the health of

 your furnace and HVAC system as a whole.

Changing the furnace filter regularly will help prevent your furnace from overheating. A clogged filter can cause the furnace to overheat, which can lead to a whole bunch of problems.

Your furnace needs good airflow to operate properly. By changing the filter regularly, you can help prevent system malfunctions and potentially reduce repair costs. It can also help prolong the life of your furnace.

Lastly, changing the furnace filter can help improve your indoor air quality (IAQ). Filters trap allergens and pollutants like dust, pet dander, pet hair, and more, keeping these particles from recirculating throughout your home.

If you’re a new homeowner or resident in an apartment, the first thing you need to do is locate the furnace. The furnace filter location will depend on where the furnace is and what type of HVAC system you have. It could be in the attic, the basement, or a utility closet. Do some checking.

Once you locate it, there should be a filter cabinet next to the furnace. The filter might also be located behind a large return air vent cover on the wall or ceiling.

The easiest way to determine this is to open the filter cabinet or vent and look at the existing filter. Most filters have the size printed on one or more sides. Common measurements might include 16 x 25 x 1, 20 x 20 x 1, 16 x 20 x1, and 20 x 25 x 1.

If the filter fits snugly, you can simply buy a replacement filter of the same size. If there aren’t any measurements listed, measure the filter. The actual size might be half an inch smaller than the size you need to buy. For instance, a 16 x 25 x 1 furnace filter’s measurements might be 15.5 x 24.5 x .7.

To make filter replacement a breeze, consider automatic delivery with Trane® Filters powered by FilterTime™.

In addition to choosing the right air filter size, you need to consider the HVAC filter’s Minimum Efficiency Reporting Value (MERV) rating. The higher the MERV rating, the more effective it is at filtering out small particles such as pollen, pet dander, and mold spores, measured in microns.

Pleated filters will have higher MERV ratings than generic fiberglass filters. Common MERV ratings are 8, 11, and 13. Their effectiveness at capturing particles like allergens and pollutants is shown in the table below.

The quality of the air filter, the MERV rating, how hard your system has been running, whether you have pets, and more can impact how often you should replace the furnace filter. In general, if you have lower MERV-rated filters, you will need to replace them more often, possibly every 30 days. Thicker filters with higher MERV ratings can be replaced less frequently, more like every 90 days.

It’s important to know that you need to change the air filter year-round. Your furnace may not be operating in the warmer months, but it acts as an air handler for your AC unit or heat pump while they are cooling your home.

Watch this video for easy directions on how to replace your furnace filter.

Putting the HVAC air filter in the wrong way defeats the purpose of the filter. So, you want to make sure that you put the filter in the right way. Look for the arrow on one of the sides (usually the top). Slide the filter in with the arrow pointing to the furnace (the arrow should point in the direction of the furnace). 

You can mark an arrow on your furnace with a Sharpie to help you remember which way to insert the filter. You can also write the date on the filter edge or use the filter reminder feature in the Trane Home app to remind you when to change it if your thermostat doesn’t notify you.

You can improve your home’s indoor air quality, enhance furnace performance, and potentially prolong the life of your furnace simply by changing the filter regularly. In addition, plan on scheduling a professional furnace tune-up each fall before heating season begins.

By Anne Fonda

LinkedIn

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

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