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Looking for professional heating, cooling and air quality advice? Our experts share helpful news, tips and tricks every other week! 
Advice from the Professionals
How To Choose And Care For Your Furnace Filter At Home

HVAC Technician replacing furnace filter.

How To Choose And Care For Your Furnace Filter At Home

The furnace filter is one of your furnace's smallest yet most significant components. It plays a major role in your home’s heating/cooling, indoor air quality, overall furnace performance and energy bills!

However, because of its small size, it usually ends up forgotten and/or neglected. In fact, this vital component becomes seemingly invisible and inconsequential to most homeowners.

However, your furnace filter, though tucked away, has an incredible impact on your home environment. If left to fend for itself, you can bet it’ll soon rear its ugly (and dusty) head. 

While you don’t see your furnace filter daily, you do see its effects on your home, health and heating bills.

In this article, we tell you everything you need to know about the furnace filter, including,

a) How it works,

b) How to care for it and

c) When to replace it.

First up!


What Is a Furnace Filter and How Does It Work?

While many people assume the job of an air filter is to purify your air, that’s actually only a byproduct of the process!

The real reason for installing a furnace filter is to protect the furnace itself.

You can typically find your filter behind a metal door in the blower compartment of your furnace.

As air returns from your home to the unit, it carries a variety of contaminants - pet dander, pollen, dust etc.

If enough contaminants accumulate in your furnace, they can damage the heat exchanger, reduce system performance and cause a shutdown.

The filter has to trap these contaminants before they reach your furnace system.


How To Care For Your Furnace Filter

Let's imagine your floors for a second.

After a few days of constant activity in your home, your floors usually accumulate quite a bit of dirt, pet hair, dander, dust etc.

This is especially true if you have a large family or pets that shed frequently.

When you see that accumulation reach a certain point, you know it’s time to haul out the vacuum cleaner.

And if you neglect the dirt on your floors, you know it will simply spread throughout your entire house.

The same is true of your furnace filter.

Over time, the filter gets clogged with air contaminants - making it difficult for air to pass through.

As mentioned above, this can damage your furnace, lowering its lifespan.

But it can also allow these harmful contaminants to continue circulating in your home - drastically reducing indoor air quality and putting your health at risk!

Another point to consider is how a clogged filter might affect your furnace efficiency.

The more clogged your filter is, the harder your furnace works to draw in and push out air.

And the harder your system works, the more energy it uses to effectively heat your home - causing your energy bills to skyrocket!

The solution?

Taking good care of your furnace filter.

Our furnace experts at Campeau Heating recommend checking your furnace filter every 30 days for signs of blockages. That could be discolouration or even a noticeable accumulation of dust.

They also advise homeowners to keep an eye, ear and nose out for the following dirty filter warning signs:

  • More dust in your home.
  • A burning smell.
  • High energy bills.
  • Low immunity.
  • Longer runtime with ineffective heating.
  • Strange noises.

If you detect any of these signs, your furnace filter needs some immediate attention.

You have two options, depending on the type of furnace filter you have.

  1. Disposable furnace filters
  2. Washable furnace filters

Our team recommends using disposable filters over washable filters for a few reasons.

Firstly, these filters are typically more effective at trapping pet dander, mould, bacteria etc.

Secondly, washable filters are not easy to clean.

And thirdly, if you damage a washable filter even slightly, they become completely unusable.

If you use a washable filter, be sure to avoid tearing or loosening the fibres as you clean them.

If you use a disposable filter, we recommend changing it at least every 90 days. And every 30 days if you have pets, a large family or family members with allergies.


How To Choose The Right Furnace Filter

Choosing the right filter for your furnace can be a confusing process.

Add to that the varying filter types, ratings and sizes, and the process gets even more difficult!

So we’ve simplified the process for you!

Below is everything you need to know when shopping for a new furnace filter.


Types of Filters

There are five main types of filters to choose from, each with its own benefits and drawbacks.


The fibreglass filter is the cheapest option but offers minimal protection.

It can trap up to 80% of particles that are 50 microns or larger and 25% of particles that are 3-10 microns.

This filter greatly improves the airflow of your heating system.

However, it does little to remove pollutants that can harm your health.


A disposable polyester filter offers more protection but is typically much more expensive.

It can trap up to 95% of particles that are 5 micros are larger.

It's also more effective in trapping pollutants that can harm your health.


The reusable electrostatic filter has charged fibres - creating static electricity. This charge allows the filter to attract particles right out of the air!

Electrostatic filters come in many MERV ratings (which we will discuss below). But to give you an idea of its effectiveness, we’ll imagine a MERV rating of 10.

With a MERV 10, an electrostatic filter can trap 85% of particles between 3-10 microns.

It can also catch almost 65% of particles between 1-3 microns.


The disposable pleated filter is a highly effective option.

It typically has a MERV rating of about 8 - meaning it can trap almost 95% of particles between 3 and 10 microns.

One of the main benefits of the pleated filter is that it can trap more particles without reducing your airflow.


The HEPA (High-Efficiency Particulate Air) filter is the most effective option.

It can trap up to 99% of particles that are 0.3 microns or larger.

Many homeowners choose the HEPA filter over any other filter because of its effectiveness. 

However, they worry that with the tight web fibres, it can be difficult for air to pass through - reducing airflow.

In the past, this pressure drop was possible. But, thankfully, the upgraded HEPA filters sold today are way more effective and energy efficient.


Air Filter Ratings

Speaking of effectiveness, let’s talk about MERV ratings.

MERV stands for minimum efficiency reporting value. And it measures the ability a filter has to trap particles between 0.3 and 10 microns.

When selecting an air filter, you’ll notice that each filter has its own rating - between 1 and 16.

The higher the rating, the more small particles the filter can effectively catch.

But don’t just go buy the filter with the highest MERV rating! It’s important to know that, while the higher ratings offer better protection, they can also reduce airflow.

Always ensure the filter you purchase is as effective as it is energy efficient. Otherwise, you might be looking at quite the expensive energy bills.


Filter Sizes

The third factor you need to consider when shopping for a furnace filter is its size.

Furnace filters are not universal. And ensuring that it’s the correct size is crucial!

Installing the wrong size filter means it cannot effectively trap particles.

Not sure what size filter furnace needs?

While filters come in a variety of different sizes, the two most common are:

  • 16 x 25 x 1 inch
  • 20 x 25 x 1 inch

But don’t take our word for it!

To ensure you get the correct size, open your furnace filter cabinet and look at the inside of the door. There should be a label there with the exact filter dimensions.


For More Furnace Maintenance Tips, Follow Along With Our Sudbury Furnace Experts!

In Sudbury, Ontario, keeping your furnace in good condition is imperative. And with winter on the way, it’s time to prepare your furnace for the cold season ahead.

For more furnace maintenance tips, keep following along! And if you have any questions about your own furnace, don’t hesitate to give us a shout.

You can reach us at (705) 560-2441 or send us a message online!

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