How to find and replace your furnace filter

How to find and replace your furnace filter



HVAC systems are susceptible to particulate matter, like dust, pet hair and dirt, entering and disrupting their airflow. To avoid this, keeping filters clean is essential. This can also improve their longevity. But how important is your air filter?

Think of a good type of filter like an unsung hero — one that works tirelessly in the background to protect your furnace’s blower fan from any pollutants drawn in from its return air duct. 

As a byproduct of trapping dirt and debris, filters also purify your home’s air quality. Over time, a furnace filter can start to wear down. It's essential to know when and how to change your type of furnace filter to ensure your home’s A/C unit performs at its prime. This article covers the ABCs of replacing a furnace filter.

Why should you replace the filter on your furnace?

Replacing a filter might seem like an insignificant maintenance ritual, but this small habit greatly impacts your home’s environment. After all, a filter is the backbone of a healthy HVAC system. Let’s understand the importance of replacing the filter on your furnace regularly.

Improve indoor air quality

An old air filter will allow dander, dust and even mold to keep circulating in your home. Since this particulate matter is too small to notice, your home’s occupants can be exposed to it for months. 

Over time, these pollutants can worsen breathing conditions, like asthma, wheezing and allergic bronchitis. A simple fix for this is regularly replacing old filters whose job is to trap these contaminants. 

Extend the life of your HVAC system

When a filter is dirty or worn down, your HVAC system — be it an air conditioner or a thermostat — has to work harder to ventilate your home. The result is more than just increased energy costs. A dirty filter places excessive strain on the blower, which can lead to prematurely overheating your HVAC unit. Constant overworking can cause your system to overheat. By replacing your filter, you instantly improve the efficiency of your HVAC system and extend its longevity.

Save on energy

When your HVAC system works as efficiently as it can, there is plenty of airflow and minimal energy consumption. This has far-reaching consequences in the amount you will save on energy costs. According to the Department of Energy, about half of your energy bill is likely from using your HVAC system. Simply replacing a dirty filter can help you reduce 15% of that monthly bill.


When should you change your furnace filter?

It's recommended to change a furnace filter about once every three months. If this is difficult to remember, consider changing your filter each time the season changes. With that said, there are additional factors that can increase or decrease how frequently you might need to change your filter:

  • Filter thickness. A thicker filter can collect more debris and does not need replacing as often as a thinner one. If your filter is thicker than 2 inches, you should be able to wait a few more months before changing it. 
  • Health conditions. If you have seasonal allergies, asthma, wheezing or other respiratory complications, regularly changing your filter every other month can help limit your symptoms. 
  • Location. A filter will likely clog faster in a more crowded or polluted city than in a rural area with less smoke. 
  • Season. In the winter season, your furnace will likely work harder to blow warm air throughout your home, which will make your filter get dirtier faster. In the summer, your air-conditioner filter might need changing since it will be used more.
  • Pets. If you have furry friends at home, their hair, dirt and dander can collect in your filter, so replacing it more frequently might be necessary.


Where is the furnace filter located?

You’re probably asking, ”Where is my furnace filter?”Before learning how to change your filter, it's important to take note of the different filter locations in your HVAC system. There are different locations because horizontal and vertical HVAC units come with more than one type of configuration. Let’s review where to find your furnace filter.

Upflow configuration

This system is made for upward airflow. Look for the blower and you will find the filter near it. This will be in the bottom door of your furnace. Open your furnace’s top and bottom doors to get to its filter.

Downflow configuration

These systems are made for downward airflow. Look for the blower to find the filter near it. In a downward configuration HVAC system, the blower will be in the top door. You will usually find two filters in this configuration. Ensure you clean or replace both. 

Horizontal configuration

Horizontal HVAC units are made for vertical airflow. You can find your furnace filter slid into a rack on the intake side of your furnace.


How to replace your furnace filter

Although being a homeowner is exciting, it requires a fair bit of DIY maintenance in the form of changing your furnace’s filters regularly. Here is a step-by-step guide on safely replacing the different types of furnace filters.

Safety considerations

Start by wearing a mask and a pair of gloves, and turn off the power to your HVAC system before opening it. Wearing a mask can prevent breathing in any particles that might become loose during the filter-changing process. 

Similarly, all the dirt, dust and debris settled on the filter will likely get your hands dirty, so putting on a pair of disposable gloves is essential. You should never change a filter without turning your system's power off because this prevents any electrical accidents. 

1. Take out the old filter

Locate your previous filter based on the configuration of your HVAC system. Once you have found the filter, take note of its size and type so you can replace it. Carefully detach your air filter from its position. Do not shake the filter, and immediately drop it into a plastic bag. Ensure the plastic bag is sealed shut and carefully discarded into your inorganic (hazardous) waste bin. 

2. Insert the new air filter

Now you are ready to insert your new air filter. Ensure that its size and kind match your system so the filter fits and works well. Air flows through the filters from the air ducts into the furnace. The filter should face the right direction to ensure it protects your furnace. To accomplish this, ensure the arrow on the new filter points toward your furnace.

3. Seal the openings around the filter

An air filter must fit snugly around your furnace to ensure no particles or contaminants can enter. Air filters should have a seal around their perimeter. If you think duct tape should do the trick, hold that thought. The temperatures around your filter are too high for a standard sealing method like duct tape to withstand. Once the duct tape has holes, it's difficult to replace it with a stronger seal. Try foil or magnetic tape, or opt for a premium seal to ensure your filter is airtight.


Things to consider when buying a new air filter

Shopping for a new air filter can be challenging for a first-time homeowner. Keep the following tips in mind to ensure your filter is the right fit. 

Make sure you have the right size

Your filter needs to fit your HVAC system’s specifications. An HVAC filter that does not fit simply won't work well. Although using the wrong size filter will not necessarily damage your system, it will impact its performance. The result will be inefficient heating and cooling, which is what you’re trying to avoid.

To determine the size of your filter, look for a number along the edge of your existing filter’s frame. Keep in mind that the size listed in bold on the frame is usually the nominal size of your filter rather than its actual size. If you can't find your filter’s measurements listed directly, measure its length, width and depth. 

MERV rating

Did you know air filters have a scale that measures how effectively they protect against dust, allergens and other contaminants? This is called the minimum efficiency reporting value (MERV). A filter with a lower MERV rating will not trap smaller particles as well as one with a higher MERV rating. This is why it is so important to determine what MERV rating your system uses. 

Are you wondering why you shouldn’t just opt for the highest MERV rating? This is because air filters with a higher MERV rating tend to have smaller pores that create resistance to airflow. If your filter’s MERV rating is higher than what is recommended by your HVAC manufacturer, this can impair its performance. In other words, your system will have to work harder (more inefficiently) to power your home’s heating or cooling system if it’s not meant to tolerate a highly resistant filter.


Protect your HVAC system from expensive repair bills with Cinch

Your HVAC system's air filter is essential to its performance. Regularly replacing it can improve your furnace’s life span. Cinch’s Built-in Systems plan provides tuneup repairs and replacement coverage for air-conditioning systems and heaters, including ductwork. 

For an affordable monthly fee, you can get normal wear-and-tear air filter replacement, a furnace or air handler tuneup, and other appliance repairs and home maintenance — along with peace of mind. Reach out today for an instant quote!


The air filter of your HVAC system can become inefficient after collected matter disrupts its airflow. Learn about how to replace furnace filters here.

Your home protection is ready and waiting!