helpful furnace tips

Do-It-Yourself: How to Replace Your Furnace Filter

In the same way that you need to change the oil in your car every 6,000 – 10,000 km to keep it running smoothly, your furnace filters need to be swapped out regularly too. Clogged or old filters are inefficient, can damage your furnace, and even drive up your energy bill as your furnace has to work overtime to do what it needs to.

Luckily, all of this is preventable with a regular filter replacement. Best of all, it’s easy to do yourself. Here are all the tips and tricks you need to know when replacing your furnace filter.

1. Follow the replacement schedule

When it comes to keeping your furnace running optimally and your air clean, regular filter replacement is essential. Changing your filter helps keep your system working more efficiently and for longer. And a more effective system means less need for furnace repairs or furnace replacement.

How to know your furnace filter needs to be changed

There are two types of furnace filters: basic and premium. Basic filters should be changed monthly. Many of the higher-end filters recommend changing every 90 days. If you have pets, a dusty environment, or have just had renovation work done, check your filter more frequently.

You can tell which filter you already have in place by pulling your existing one out to take a look. The premium filters are typically pleated and opaque, the basic are flat and more translucent. 

No matter which type of filter you use, we suggest checking your filter each month just to be sure it’s in good condition. As a general rule of thumb, if the filter is looking grey and dirty it’s time for a new one.

Some other signs that it is time to change your filter include:

  • Energy bills creeping up
  • Increased sickness or allergy symptoms
  • More dust in the air (or collecting on countertops, floor, and furniture)
  • It takes longer to heat your home (due to the short cycling furnace)
  • When in doubt, it’s good to replace the filter
Did you know? Your furnace filter also filters out dust and debris when you are running your air conditioner. Both systems use the same ducting to distribute air throughout your home but air conditioners are even more sensitive to airflow than furnaces. They can freeze up and stop working without adequate airflow. That’s why it’s important to check your furnace filter regularly during the heating AND cooling season.

2. Find the right filter for your furnace and lifestyle

When you walk into the furnace filter aisle in a hardware store, it can be overwhelming to look at all the options available. From the size of the filter and impurities you want to remove, to the price and name brand, there are a lot of things to consider before you head to the check-out aisle. We asked the experts to weigh in on furnace filter selection, and here’s what they had to say.

Choose the right furnace filter size

Yes, different furnaces require different filter sizes, so it’s important that you select the right size for your furnace. Furnace filters are sized by width, length, and thickness. The easiest way to tell is to check the dimensions on the filter that is currently in the furnace before you go shopping.

When it is time to swap out your filters, it’s important to make sure that you’re getting the right size filter for your furnace. To find the size of the filter you need just pull out your existing filter and check along the sides where the dimensions should be listed.

Alternatively, the owner’s manual for your furnace should tell you what size you need. If you can’t find the manual, you can always google your make and model.

Standard-format filters — microparticle rating

Different filters have what’s called a “microparticle rating”. The higher the rating number, the smaller particles can be removed from the air. A basic filter will be a 300 microparticle rating and will remove dust and lint. A midrange filter, at 600 microparticles, will also capture dust mite debris and mold spores. Allergy-rated filters (rated around 1,000 microparticles) will help with pet dander, pollen, and smoke. And the high-end filters, at 1,500 microparticles, can remove bacteria viruses and odors, and maximize the air quality. Naturally, the price goes up when the rating does.

You may be surprised to learn that many professional furnace cleaning companies will recommend a basic filter for most furnaces, as long as it is replaced on a monthly basis!

The reason is that thicker filters with higher ratings tend to clog more quickly, making the furnace work harder, causing a reduction in efficiency and prematurely wearing out parts. The good news is that basic Fibreglass type filters are available at a fraction of the cost, come in bulk quantities and there are several non-brand name options, so it can actually be cheaper to use these filters even with the increased replacement frequency.

It is worth considering higher-end filters if you have allergies, pets, or an older home with mold or mildew issues.

Depending on your lifestyle (pets, dusty hobbies like woodworking, etc.) and your preference, there are different types of filters with varying levels of ability to catch these smaller particles from the air. This can be identified by what’s called a microparticle rating. The higher the rating number, the smaller of particles it can remove from the air. For example, higher range filters (known as allergy-rated filters) can pick up pet dander, pollen, and even smoke and are rated around 1000 microparticles. Your most basic filter, rated at roughly 300 microparticles, will pick up mostly dust and lint. Each filter is priced accordingly, so expect to pay more for the higher number of microparticle ratings.

Large-format filters – MERV rating

For large-format filters (typically 4-6” thick) there’s an entirely different rating system, the most common of which being the MERV (Minimum Efficiency Reporting Value) rating. Filters with a rating between 5 – 8 MERV are equivalent to the filtration a basic standard filter offers and will capture particles 3.0 – 10.0 um (short for tiny particles known as micron’s). A 9-12 MERV rated filter will catch particles as small as 1.0 – 3.0 um and remove 90-98% of particles in the air. 13 – 16 MERV rated filters will capture particles as small 0.3 – 1 um and remove 95- 99% of particles from the air. This level of filtration is equal to what is used in surgical operating rooms. MERV 17 Level filtration is equal to filtration delivered by a HEPA Filtration System. As with standard filters, as MERV rated filters increase infiltration ability, they also increase in price.

How much should a furnace filter cost?

A top-end filter can cost as much as $50/filter. It will last longer, and also provide better filtration. But as we mentioned, for most homes, a basic filter will do just fine. In most cases, you can save money by purchasing a pack of 3 filters versus buying a single filter.

Generic is okay

While there are several different sizes and ratings, there are a number of different brands available on the market. In the end, all that matters is the performance, not the logo.

Don’t forget to double-check that you bought the right one before opening the package so you can return it if you need.

3. Install the new filter

This part might seem easy, but unless you deal with furnaces often (let’s hope not) there are a few important things to remember:

Follow the arrow — When you install your new filter, make sure the airflow arrow (printed on the top or side of the filter) is pointed towards the furnace. This arrow is the direction of air flow.

Don’t force it — As you install your new filter, it should slide in gently and without the need for force. If it feels at all like it’s sticking or difficult to get in, try removing it altogether and doing it again. If you force the filter, it might bend or break.

Re-install the filter cover — You want to keep dust from entering your furnace – and your home. Filter covers are designed to fit over the filter slot to keep everything contained. Most newer furnaces come with filter plate covers to protect you and your furnace. Be sure to put your filter cover back in place once you’ve swapped out your filter. Keep in mind that filter covers are required by most local building codes as they prevent the furnace from drawing air in the furnace room and circulating this air through the house.

4. Set a reminder for next time

Owning a home can involve a regular amount of upkeep, so we recommend setting helpful maintenance reminders for yourself. One of the ways to do this is by writing the date the filter was installed on the side of the furnace filter (permanent markers work well for this). Want to automate it? Set a calendar reminder in your phone for a monthly check-in.

A little care can go a long way

We hope that after reading this article you’re feeling more confident than ever to update your furnace filter. And if this sounds like a lot of work, we’re here to help. Give us a call to schedule your regular furnace upkeep and maintenance.

You can read more about maintaining your furnace in our Homeowner’s Furnace Guide.