Choose you air filter

05/03/2017 2 Comment(s)

Many people question themselves on what type of air filter to use for their forced air heating system. Before answering that question, let’s answer this one: what use does a filter have?The air filter’s use is to protect the heating system’s equipment. The first purpose of the air filter is to prevent the accumulation of residue or debris in the furnace and on the interior coil of the central heat pump or air conditioning.


The air filter can also help to reduce the risks to certain respiratory problems, by reducing the presence of contaminants in the air. However, know that no residential heating system air filter can claim to 100% filter allergens, contaminants, dog hair, etc.  A forced air heating system does not stir enough air in the house to have the pretention of being able to circulate every meter cube of air in the house through the furnace’s air filter. The air in the house is generally drawn up by 2 or 3 registers (air returns) of less than one meter cube, and this, for the entire house. The dust has a bigger chance of ending up on the floor instead of in your furnace’s air filter. Same goes for everything that is found in the air of your home. It goes without saying that you still vacuum your home despite the fact that you change your air filter regularly.

In order to choose well one’s filter, it is absolutely essential to be able to evaluate its filtration capacity. In 1987, the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) created a classification system called MERV (Minimum Efficiency Reporting Value) graded from MERV 1 to MERV 20. This classification is known and used throughout North America. For residential areas, it is recommended to use a filter whose capacity ranges from MERV 5 to MERV 12. 


If you use an air filter of MERV 13 capacity or more, there is a risk that you will create a restriction problem with the air circulation. The filter being too efficient (it filters the tiniest of particles), it will make it more difficult for the air to pass through. It might then be difficult for your system to have the heat or cold circulate which could cause some of the following problems: freezing of the coil, breaking of the drain pan due to an overheating, breaking of the fan motor, extra consumption of electricity, etc. This type of filter is expensive and requires regular replacement because of its great efficiency. It is very rarely used for residential purposes. It is important to use an air filter that respects the recommendations of the furnace’s manufacturer. Consult the following chart to better understand the MERV classification:








0.3 - 1μm


1.0 – 3.0 μm


 3.0 – 10 μm

Polluting Agents


MERV 1 to 4




Hair, rug fibers, insects

Solely for residential pre-filtration

MERV 5 to 8



20 to 85%

Pollen, dirt dust, mildew spores 

Residential and commercial (average quality)

MERV 9 to 12


50 to 90%

85 to 90%

Flour dust, combustion soot, legionella

Residential and commercial (high quality)

MERV 13 to 16




Cigarette smoke, make-up powder, bacteria

Institutional (top range)

MERV 17 to 20




Combustion smoke, viruses

Clean rooms, pharmaceutical industries, etc.





Our Maxi Merv 11 filter offers:

  • A greater protection for the coil due to the Merv 11 higher level of filtration
  • A longer life span due to the high number of pleats
  • A filtration capacity up to 1 micron
  • A product of the highest quality recommanded by the CETAF and CMMTQ


Our Ultra Merv 8 filter offers:

  • A standard protection for the coil due to the Merv 8 filtration capacity
  • A life span of approximately 4 months for a 4 inchs thick filter
  • A filtration capacity up to 3 microns
  • A product of quality recommanded by the CETAF and CMMTQ


Our Standard Merv 8 filter offers:

  • A standard protection for the coil due to the Merv 8 filtration capacity
  • A life span of approximately 3 months for a 4 inchs thick filter
  • A filtration capacity up to 3 microns
  • A product of quality recommanded by the CETAF and CMMTQ

The higher the MERV capacity, the better the air filter will filter small particles. The higher the number of pleats, the more material there is, the longer the life span of the filter will be. We have placed, side by side, our 3 main air filters; MERV 8 Standard, Ultra MERV 8 and MERV 11 Maxi:


As you can see, the MERV 11 filter has a lot more pleats then the two other filters. It offers the optimal level of filtration thanks to it's higher longevity and its capacity to filter particles as fine as 1 micron.  The Merv 8 ultra  and the Merv 8 standard filter offers an adequate protection for your interior coil.  The Merv 8 ultra will last longer than the Merv 8 standard filter thanks to is higher number of pleats.




 The accumulation of dust and dirt can considerably affect the performance of your heating system. A clogged interior coil will be inefficient, which will consequently have your heat pump or air conditioner produce less heat or air conditioning. If the equipment is inefficient, your system will have to function longer in order to maintain the desired temperature, thereby raising your energy costs. A clogged interior coil will corrode a lot quicker than in a normal functioning situation which could result in expensive repairs. We recommend that the verification and replacement of the filters be done on a regular basis.  


*Chart adaptation according to data on page 2.28 of the Guide des bonnes pratiques en ventilation mécanique produced by the Corporation des entreprises de traitement de l’air et du froid (CETAF) and by the Corporation des maîtres mécaniciens en tuyauterie du Québec (CMMTQ). 

2 Comment(s)

Éric Sauvageau:
26/05/2017, 10:36:54 AM

À quelle fréquence devrais-je changer le filtre MERV 11? Merci beaucoup!

Thermopompe N & R Sol:
14/02/2018, 03:46:36 PM

La fréquence de remplacement d'un filtre à air dépend de plusieurs facteurs: s'agit-il d'un filtre à air de 1", 2" ou 4" d'épaisseur, est-ce qu'il y à des animaux dans le domicile, êtes-vous dans un secteur où il y à beaucoup de circulation automobile, est-ce que vous laissez vos fenêtres ouvertes en été, est-ce que vous cuisinez beaucoup, effectuez vous présentement des rénovations, etc. En général, nous conseillons à nos clients d'effectuer une inspection visuelle du filtre selon l'épaisseur du filtre et selon la fréquence suivante: 1", à chaque mois, 2", à chaque 2 mois, 4", à chaque 4 mois, 5", à chaque 6 mois. Si vous voyez que le filtre est rendu gris et surchargé, alors remplacez-le. Si on voit encore parfaitement la couleur du média filtrant, refaite une inspection le mois suivant.

Assunta Vardaro:
15/06/2021, 10:23:10 AM

I need filters for AC units 6-1/2 “ x 21 “x 2” Please quote price for box of 12

Thermopompe N & R Sol:
03/06/2022, 02:08:44 PM

Hello, those are not standards dimensions. We do not currently provide quote for on demand dimensions. Regards.

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