How to Change a Furnace Filter (Video & Steps)

Regularly changing your furnace filter is a simple task that you can do yourself to improve your home's air quality and efficiency of your heating and cooling system. Whether you live in a house with a primary heating or cooling system such as a furnace, heat pump or a condo building with a centralized HVAC system, knowing how to change a furnace filter is essential.

Skill Level: Beginner

Time: 15 minutes

There are 5 steps to completing this project:

Step 1: What Size Filter Do You Need?
Step 2: Locate Furnace and Turn Off Power
Step 3: Find the Filter Slot
Step 4: Which Way Does a Filter Go in the Furnace?
Step 5: Turn the Power Back On

Air Filter

Handheld Vacuum

Microfiber Cloth

What Type of Furnace Filter is Right for Your Home?

Before we dive into how to change a furnace filter, let's explore the two main types of furnace filters available and how to select the best one for your needs.

A box of HDX pleated air filters is shown, detailing the MERV 8 rating and 90-day performance.

Fibreglass Filters

These are the most common and affordable filters. They are designed to protect your furnace from large particles like dust and lint but offer minimal protection against smaller allergens. They are a good choice for those on a tight budget or in homes without allergy sufferers, but they need to be replaced frequently – about once a month – to be effective.

Electrostatic pleated air filters

These are the most effective at reducing allergens and small particles in the air. They trap particles including dust mites and pet dander and are highly recommended if a member of the household smokes. The pleats in these filters also allow for increased airflow and should be changed every 30 -90 days for 1-inch deep filters and 6-12 months for 4-, 5- and 6-inch deep filters.

How to Choose the Best Furnace Filter for your Lifestyle?

A chart that compares different MERV ratings (from 8 to 14) and what airborne particles they can filter, such as household dust, pet dander, pollen, and bacteria.

A few questions to ask before you choose the best filter for your home are:

Do you have pets at home?
How many people live in the home?
Does anyone in the home have allergies, asthma, or other breathing issues?
Are there concerns about smog, pollution, or wildfire smoke?

How to Choose the Best Filter for Your Lifestyle:

Filters for Allergies/Asthma: Choose a pleated filter with a higher MERV rating (8-13).
Filters for homes with Pets: A pleated filter with a MERV rating of 8 or higher is recommended to capture pet dander.
Filters for a Tight Budget: Fibreglass filters are the most economical option.

Understanding MERV Ratings:

The MERV (Minimum Efficiency Reporting Value) rating is the industry standard used across all brands to measure how well filters capture airborne particles. The higher the MERV rating, the greater the efficiency to trap smaller particles. Keep in mind that a higher MERV rating also means the filter material is denser, which can increase energy consumption as the HVAC system works harder. You might also see MPR ratings on certain filters, which is specific to the 3M brand. For most Canadian homes, a MERV rating of 8 is a great all-around choice.

How Often Should You Change Your Furnace Filter?

A graphic with two orange circles shows that 1" filters should be changed every 3 months

Most 1-inch deep furnace filters will last up to 3 months and specify 90-day airflow performance on the packaging. 4-, 5- and 6-inch deep air filters will last 6-12 months. Depending on where you live and environmental factors such as pets, pollution, and wildfire smoke, you may need to replace your filter more often. Fibreglass air filters are rated for only 30 days.

Step 1 What Size Filter Do You Need?
Before removing the old filter, make a note of its dimensions, which are usually printed on the cardboard frame (e.g., 16 x 25 x 1 which is one of the most popular sizes). If you can’t find dimensions, you’ll need to use a measuring tape to get an accurate measurement and check actual size vs nominal size. Also, observe the airflow direction arrow on the side of the filter. The arrow should point towards the furnace.
Step 2 Locate Furnace and Turn Off Power
Your furnace is typically located in the basement or a utility room. Before removing the furnace filter, you should always turn off the power to the furnace first. There should be a dedicated switch on or near the unit, which looks like a regular light switch. Flip it to the "OFF" position. This is a critical safety step and prevents dust and debris from getting into your HVAC system. In a condo building, find out if you are responsible for changing your filter. In some buildings, this is part of a routine maintenance service provided by building management. If you can’t locate a power switch, you can also turn off power to the breaker on your electrical panel.
Step 3 Find the Filter Slot
The filter slot is a rectangular opening on the return air duct, often on the side of the furnace unit itself. In a condo, the filter is often located behind a return air grille, which may be on a wall or in the ceiling of a hallway or a common area. The grille will have a latch or screws holding it in place. If your unit has a fan coil or heat pump system (often located in a closet), the filter will be in a dedicated slot on the unit.
Step 4 Which Way Does a Filter Go in the Furnace?
Ensure the airflow arrow on the new filter points in the same direction as the arrow on the old one (towards the furnace). Remove the old filter and clean any dust or debris in your HVAC unit with a cloth or vacuum. Slide the new filter into the slot until it is fully seated. You can write the date on the filter frame with a marker to remember when you last changed it. Discard of the old filter in your household garbage in a plastic bag to contain dust and dirt.
Step 5 Turn the Power Back On
Restore power to your furnace and you're all set. By changing your furnace filter on a regular basis, you can enjoy cleaner indoor air, help lower your energy bills and enjoy a longer life for your heating and cooling system.

How to Change a Furnace Filter