How to Change Your Furnace Filter: A Step-by-Step Guide

Maintaining your furnace is essential for keeping your home warm, your energy bills low, and your air clean. One of the simplest ways to do this is by regularly changing your furnace filter. If you’ve never done it before, don't worry—it’s easy! This guide will walk you through the process step-by-step.

Why You Should Change Your Furnace Filter

Furnace filters trap dust, debris, and allergens from the air circulating through your home. A dirty filter can clog up your system, causing poor airflow, making your furnace work harder, and potentially leading to costly Overworked systems can even pose a fire risk, especially when airflow is restricted​.

Changing your filter every few months ensures your system runs smoothly, keeps your air clean, and reduces the risk of damage to your HVAC equipment​

Step 1: Turn Off Your Furnace

Before doing anything, it’s important to turn off your furnace to avoid any safety risks. You can usually do this by flipping the switch next to the furnace (which looks like a regular light switch) or turning off your thermostat​.

Step 2: Locate the Furnace Filter

Furnace filters are usually found in two common locations:

• Inside the furnace: Open the access panel or door near the furnace, typically located on the return air side, which brings air into the furnace​

• Behind the return air vent: In homes where the furnace is in an attic or crawl space, the filter might be installed behind the return air vent, typically near the thermostat​.

Step 3: Remove the Old Filter

Slide the old filter out of its slot. Check how dirty it is by holding it up to the light. If you can’t see light through it, it’s time for a replacement. This is a good way to determine whether your filter is clogged and needs replacing​

Step 4: Find the Right Replacement Filter

Every filter has a size printed on its cardboard edge (e.g., 16x25x1). This is crucial when buying a new one. Simply snap a picture of the size or write it down, and take it to your local hardware store, Home Depot, or Lowe’s. Most stores carry these filters in stock or can get them quickly​

You’ll also need to decide on the type of filter. Here's a quick breakdown of common options:

• Fiberglass filters: Inexpensive but don’t trap small particles​.

• Pleated filters: More efficient and trap smaller particles like dust mites and pollen​.

• Electrostatic filters: Can be either disposable or washable and are effective at trapping smaller particles​.

It’s generally recommended to choose a filter with a MERV rating between 6 and 12 for residential use. Higher MERV ratings (above 13) can restrict airflow, making the system work harder​.

Step 5: Install the New Filter

Installing the new filter is easy:

1. Look for an arrow on the edge of the filter. This arrow shows the direction of airflow, and it should point toward the furnace or blower motor.

2. Slide the new filter into the slot.

3. If you removed an access panel or cover, replace it​.

Step 6: Turn the Furnace Back On

Once the filter is installed, turn your furnace back on. Your HVAC system should now be running more efficiently, providing cleaner air and better airflow throughout your home​.

How Often Should You Change the Filter?

It depends on several factors, including the type of filter you use, how much dust and pet dander is in your home, and whether anyone in the household has allergies. A good rule of thumb is to check your filter every 1 to 3 months. Fiberglass filters should be replaced more frequently, while pleated filters can last up to 3 months​.

If you’ve been running your furnace fan non-stop or have been using your system more frequently due to extreme weather, you may need to check the filter more often.

Common Problems Caused by Dirty Filters

Neglecting to change your furnace filter can cause:

• Poor indoor air quality: A clogged filter doesn’t effectively trap dust and allergens.

• Higher energy bills: A dirty filter forces your furnace to work harder, consuming more energy.

• System malfunctions: Restricted airflow can overheat the blower motor, leading to costly repairs or breakdowns​.

Need Help?

If you're not confident doing this yourself, don't hesitate to ask for help! If you're in the East Bay, feel free to contact me—I’d be happy to swing by and assist. We can also take a walk around your property and talk about other maintenance tasks to keep your home in top shape. Alternatively, I’m happy to guide you through it on FaceTime if that’s easier.