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FAQs

Filters are designed to trap dust, dirt, and airborne particulates before they can get into the system and cause damage to your furnace. Filters improve the air quality in your home by trapping bacteria, pollen, and mildew and mold spores. Since the air in your house circulates through your HVAC system, furnace filters are your first line of defence against dust and airborne allergens.

Not changing your furnace filter on a regular basis will also cause your system to work harder and consume more energy. When your filter gets dirty, it's also getting clogged up which is making your blower motor work harder thus consuming more energy to maintain the temperature in your home. By regularly changing your filter, you will ensure that your furnace works efficiently and the cost of your filters are actually paid for by the decreased energy cost and pre mature maintenance, repair or replacement of your furnace.

It's false economy to try to extend the life of filters beyond their specifications. Any money you might save on the filters themselves is lost on higher energy bills. If anyone in the household has respiratory difficulties, you're also making things tougher on them


  • Manufactuers recommend to change your filter at a minimum every three months. Leaving it longer will cause your furnace blower motor to work harder and use more energy thus costing more to operate your furnace and may lead to pre mature wear and tear on your furnace.
  • You notice excessive to moderate dust buildup in your house

The examples below will help you determine how often to change your filter.

Example household requiring a new filter every 45 days:

Family of six lives in the same household, everyone chips in to take care of Grandma, who lives with them, and has emphysema. They don’t have any pets because the children seem to have the same allergies that their mother does, but occasionally host friends and family.

Because most of the family have allergies and the grandmother has a severe breathing problem, and because there are six people bringing contaminants in as opposed to one or two, changing their filter more often is in their best interest.

Example household requiring a new filter every 60 days:

A family of five with children between the ages of 8 and 15. They’re all healthy kids who are into sports, and their parents enjoy hosting team dinners for each of their chilren, who have friends over often either way. They also have a young golden retriever.

No one in this family suffers from a breathing condition but more dirt, dust and other contaminants find their way into this home every time they have guests over. Charlie the golden retriever joins the guests and family members themselves in churning up these contaminants within their home, and leaves behind pet dander.

Example household requiring a new filter every 90 days:

Perhaps one household is comprised of newlyweds or a single person. They have no pets, neither of them smoke and they rarely have guests over, they have no allergies, they don’t smoke and don’t often have guests over to bring in dust and dirt.

A furnace filter seems to be an insignificant component of the furnace or A/C system, but good airflow is really important. If your furnace filter is clean, it allows for efficient air flow. If it's really clogged and holding a lot of debris, it will force your hvac system to work harder. In turn, this will bring higher energy bills and reduced air quality.

It's false economy to try to extend the life of filters beyond their specifications. Any money you might save on the filters themselves is lost on higher energy bills. If anyone in the household has respiratory difficulties, you're also making things tougher on them.

Changing the filter is a fairly easy task. Again, consult your manual for proper procedure, but typically the process for how to change a furnace filter goes as follows:

  1. Turn off the furnace.
  2. Locate the service panel and remove it.
  3. Slide out the existing filter (located near the intake/outtake blower fan).
  4. Slide in a new filter with the harrow pointing in the same direction as the air flow. If you're not sure, the air comes-in to your furnace through the "return" duct work, gets cooled or warmed and then gets pushed back in your home through the "supply" duct.
  5. Turn the furnace back on.

Before you go ahead and make your purchase, you need to know the size of the air filter you need. Your owners manual will also help you in determining your filter size. It's important to get the right size, as there's no room for maneuvering. Furnace filters either fit or they don't.

Furnace filters are sized by height, length, and depth (thickness). The thickness can range from an inch to up to five inches. The most common furnace filters are 1”, 4” and 5” in thickness. Height and length combinations range from 10x10 and all the way up to 30x30. You can easily check the size of your old filter in place - the size is typically shown on the cardboard filter frame. The common sizes used across Canada and the US for one inch filters are 14x25x1, 16x20x1, 16x25x1 and 20x25x1.

Sizing should be clear from your existing filter and will be given as the length x height x thickness – 16x25x1furnace filter, for example. These measurements are in inches, but the inch marking is not normally shown.

Most filters are one inch thick, but some are two inches, four inches and five inches in thickness. In theory, a thicker filter gives greater filtration – but they aren't interchangeable. If the existing furnace filter is 1 inch thick, a four inch filter will not fit without having to modify the opening to your hvac setup. Even if that were practical (which is unlikely), your system might only have sufficient airflow for a one-inch filter anyway. Putting a thicker version in could actually reduce effectiveness.

The vast majority of disposable furnace filters are rated according to the MERV rating scale (minimum efficiency reporting value) created by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. The higher the number, the finer the filter, so the more particles it traps.

Disposable filters offered for household use vary between MERV 6 and MERV 13. However, experts recommend MERV 8 as a minimum and MERV 11 for better filtration of airborne particles.


MERV 11 MERV 13
  • Pollen
  • Lint
  • Dust
  • Mold
  • Mites
  • Bacteria
  • Skin Flakes
  • All from MERV 11 plus;
  • Pet Dander
  • Cooking Oil
  • Virus Carriers 
  • Smoke
  • Smog

Manufacturer claims such as removes 95 percent of dust are meaningless without knowing the size/type of particles you are discussing. A very poor (airy) filter can trap 95% of larger particles but only 3% of very small particles. Filters that claim to remove, say, 99% of pollen or mold, are sometimes basing that on removing whole pollen or mold grains and do not factor in particle fragments (they break up into finer particles).

Running the HVAC system on continuous fan is the best way to clean the air regardless of the type of filter you use.

Less-efficient filters get more efficient as they load, since the pores begin to fill, spaces between the media fibers get smaller, and they start trapping finer dust. Of course, this also means the filters are clogging and will soon obstruct airflow.

How often you need to change the filter will depend on how efficient it is, how much you run the fan on your HVAC unit, and how many dust sources you have inside.

HVAC systems and filters are like vacuum cleaners. They should move enough air to clean the environment without allowing the dust to blow back into your home. Replacing you furnace filters regularly helps your system perform at its best. 

The average price for a MERV 10/11 16x25x1 filter, which is the most common size, when purchased individually from the big box stores is $21.99 compared to $19.99 with Onefiltra delivered to your doorstep every 45, 60 or 90 days. The average bulk price from the big box stores for the same filter is $15, however, if you forget to change your filter, you negate the cost savings by spending more on your hydro bill.

For the same size filter but with a MERV rating of 13, the average price at the big box store is $28.52, the lower price being 23.15 when purchased in bulk and as much as $36.49. Onefiltra’s pricing for the same filter is 24.99 delivered to your doorstep.

4” Filters

The average price for a MERV 10/11 4” filter at a big box store is $47, compared to $34.99 with Onefiltra delivered to your doorstep. For 4” MERV 13 filters, the average big box price is $52, compared to $39.99 with Onefiltra.

5” Filters

The average price for a MERV 10/11 5” filter at a big box store is $48, compared to $44.99 with Onefiltra delivered to your doorstep. For a 5” MERV 13 filter, the average big box price is $53, compared to $49,99 with Onefiltra.

We’d like to think that breathing cleaner air and the added convenience along with savings in your time and on your hydro bill makes Onefiltra the smart decision. Another major factor to consider is that by changing your filter on a regular basis, you’re also preventing unnecessary and pre-mature furnace maintenance expenses down the road.

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