Commonly Asked Questions About Furnace Filters

Commonly Asked Questions About Furnace Filters

Nadir Chaudhry25/3/20

When it comes to home maintenance, there are a few things that people tend to ignore – one of those being their furnace air filters. For many, regularly changing your air filter doesn’t seem like a big deal and because it’s either inconvenient or too costly, a number of households neglect this part of their home.

You might be here because you’re wondering what all the big fuss is about. What does an air filter do, exactly, and why is it so important to change it regularly? And if you are here because you want to start changing it, you may have questions about what kind you need and so forth.

Helping You Maintain Air Quality

PureFilters is a company dedicated to helping Canadians achieve happier and healthier homes with quality air. We sell replacement MERV 11 furnace filters among others through our online store at affordable prices. By cutting out the middle man (big box retailers and contractors) we are able to get our supply directly from top Canadian manufacturers and sell at a reduced price to our customers.

Not only are we committed to providing quality products to Canadians, but we also aim to educate the public about the importance of having quality air in their homes. Let’s take a look at some of the top questions you may have about air filters.

What Does a Furnace Filter Do?

In order to properly understand the purpose of a furnace filter, it’s important to first know how a furnace works.

A traditional furnace draws air in via the return ducts, warms the air over a heat exchanger, and then with a blower fan, pushes the now heated air through a series of ducts that branch off into rooms throughout a home. The ‘forced air’ furnace will continue to run until the temperature inside reaches a level designated by the thermostat setting.

A furnace filter is designed to protect the blower fan from all the dust, debris, and other small particles that the return duct pulls in from the home. These particles and other contaminants get caught in the filter and are prevented from getting into the furnace and eventually recirculated back into the home.

Why Should I Regularly Change my Filter?

There are a number of benefits to changing your furnace filter on the regular.

Improved Air Quality

If your filter is clogged it will be unable to capture potentially harmful contaminants from things like pollen, dust, dander, fibres, mould, smoke, etc. Consequently, these contaminants get circulated back out into the home and the air you breathe.

Poor indoor air quality tends to affect people with allergies, children, and the elderly the most, but it can also affect the average person as well. People can develop allergies or have other side effects like headaches, poor sleep, skin, throat, nose, or eye irritation, and even develop more serious conditions.

Reduced Energy Bills

A furnace with a clogged filter will invariably need to work harder and use more energy to warm the home as it struggles to push the warm air out. Research shows that a clean filter can lower your energy use by as much as 15 percent, saving households about 7.5 percent on their monthly bills.

Avoid Unnecessary Repairs

As your furnace struggles to heat your home because of a dirty filter, it can overheat and get damaged and need emergency repairs. The motors of old units are particularly vulnerable to this occurring. If this happens, your only option is to replace the motor which can be costly, and in the meantime, you’re left without a way to heat your home which can lead to other costly issues (i.e. frozen and bursting pipes).

How Often Do Furnace Filters Need to Be Replaced?

As a general rule of thumb, your filter will need to be replaced more often if:

  • You have high levels of pollutants in the home (i.e., a smoker lives in the home or if you have pets).
  • There are children or elderly people in the home who are particularly sensitive to pollutants in the air.

Besides these factors, there are general guidelines that have to do with the thickness of your filter:

  • 1 and 2-inch filters: change every 1 to 3 months
  • 3 and 4-inch filters: change every 3 to 6 months
  • 5 and 6-inch filters: change every 6 months

What Kind of Filter Do I Need?

In order to determine what kind of filter you need, you will have to measure your current filter. Your existing filter typically will show two sizes, the “nominal size” and the “actual size.” The nominal size is used by companies for marketing purposes, and is basically the actual size but rounded up or down to get an even number.

So if your filer is measuring at an actual size of 15½ x 24½ x ¾ then what you need is a furnace filter 16x25x1 which is its “nominal size.”

What Are MERV Ratings?

Designed by the ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) in 1987, MERV stands for minimum efficiency reporting value and is a way to measure the effectiveness of an air filtration product.

The MERV scale ranges from 1 to 20. MERV 1 filtration filters can capture particles as small as 10 microns with 65% efficiency, and on the higher end of the scale MERV 20 filtrations can capture particles as small as 0.3 microns with 95% efficiency.

So what is the best MERV rating for furnace filters in the average home? The most common MERV ratings you’ll see are 8, 11, and 13. Most homes can manage with MERV 8, but if your home often has high levels of pollutants (i.e. a smoker lives there or you have pets) higher is better.

Where Should I Purchase New Filters?

The answer to this one is simple: at! We have a robust inventory of filters all at affordable prices. Fully Canadian owned and operated, there’s no better place to find quality air filters you can count on.

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