26 Feb. 19

How to Choose the Right Filter for Your Furnace


The air quality of your home is important if you want to enjoy living in it. Maintaining air quality is the primary function of your cooling and heating devices. If you own a furnace, your furnace has an air filter that determines the quality of air flowing through your home.

Using the right air filter for your furnace is essential if you want to enjoy its services. It goes a long way to improve your user experience. Particles and residue swirl around in the atmosphere of your homes. It is the function of your air filters to remove this residue, thereby improving the quality of the air you breathe in.

Your furnace’s filters should be changed regularly. At the very least, you should change your filters once every couple of months. Air filters help your heater to work more efficiently. If you leave them unchanged, it won’t be long before the performance of your furnace is impacted negatively.

Deciding to change your filters is one thing while selecting the right filter for your home is another. There are different types of air filters available for you to buy. Similarly, there are a number of factors that you have to take into consideration. Keep reading to find out how to select the perfect air filter for your furnace.

Related article: The Ultimate Furnace Maintenance Guide: Tips & How To

The Size of Your Air Filters

Size is one of the most important factors that you have to consider when it comes to air filters. It is imperative that the new filter you are buying is the right match for your furnace. Usually, the size of air filters is written in the form, length x width x height.

Air filters come in a wide range of sizes. If you buy a filter that is too big for your filter cabinet, it won’t fit into it. On the other hand, filters that are undersized won’t stay in the filter cabinet. It may end up falling into the return plenum causing obstruction of airflow. Either way, your filter won’t be able to do what it is meant to do: remove contaminants from your air supply.

Most air filters come with their dimensions printed on them. Before you buy an air filter, check your current filter to know what size your furnace needs. If your current filter does not have its dimensions printed on them, check the model number and look its size up online.

MERV Ratings

Air filters are designed to trap dust, debris and small residue circulating the atmosphere of your home. The effectiveness of your air filter at doing this is a function of its MERV (Minimum Efficiency Reporting Value) ratings.

This rating is a measure of your filter’s efficiency at trapping particles with sizes that range from 3.0 to 10.0 microns. MERV ratings start at 1 and end at 20. The higher the MERV rating of an air filter, the higher the number of particles it can filter.

It may look like all you have to do is buy an air filter with a high MERV rating, but that is not always the case. The right MERV value for your filter depends on the peculiar needs of your household as well as your heating demands. Filters with higher MERV values offer maximum contaminant filtration.

However, they are not necessarily the best option if your furnace is not made to work with this type of filter.

To determine the best air filter for your furnace, the best option is to consult your furnace manual. Additionally, it might be prudent for you to discuss your options with an HVAC expert beforehand. They will be able to provide you with an informed selection that is appropriate for your furnace.

Note that even homes with the same furnace models may not use filters with the same MERV ratings. Environmental factors, as well as air quality, affect the MERV ratings of your filter.

Types of Filters

When selecting a filter for your home furnace, there are different types of air filters that you can purchase. They include:

1. Disposable Fibreglass Filters

These types of filters are the least expensive filters available in the market. Disposable fibreglass filters are made to trap large dust particles. However, tinier particles such as pollen can pass through.

Fibreglass filters are very cheap, so much so that most people don’t bother to clean them. They’d usually dispose of them and then buy new ones.

2. Polyester Filters

Polyester filters are very capable of trapping between 80-95 percent of particles measuring 5 microns or larger. They are made using the best materials. As far as sizes go, they are recorded as medium-sized.

Due to their increased efficiency, they are a little bit on the pricey side. If your goal is a filter that traps unwanted particles efficiently, polyester filters are a great fit. You should note that the high MERV ratings of polyester filters mean that they would be extra prone to clogging. You would have to maintain them regularly.

3. Washable Electrostatic Filters

These filters use an electrode to produce an electrostatic charge which eliminates particles, pollen and mould spores from the atmosphere. They are so efficient that they can remove 94% of tiny particles as well as 80% of viruses (airborne) from your heating system.

Washable electrostatic filters can be a little bit on the expensive side. However, you will be able to use them for a very long time since they are washable. Additionally, they are very effective at protecting the air quality of your furnace and home.

4. Permanent Electrostatic Filters

Crafted from fibres that charge themselves, these filters practically attract particles from your air. They have a MERV rating of 8. Hence they are excellent at reducing the number of pollutants in your air supply. Before, buying an electrostatic filter, it is vital that you make sure its high MERV ratings are compatible with your filter.

5. Fibreglass Air Filters

You probably guessed it. These type of air filters are constructed from fibreglass. This leaves them with a flat surface. Fibreglass filters are not very effective at removing unwanted particles from your living space. However, they do a pretty good job of protecting your furnace from unwanted debris.

The MERV rating of the average fibreglass air filter ranges between 1 and 4. They are also cheap.

6. Pleated Air Filters

They are constructed majorly from a polyester material. They have a pleated outer surface, a fact that adds to the efficiency of these filters. At the very least, pleated air filters can get rid of 45% of pollutants swirling around in the atmosphere. Their MERV ratings typically start at 8 and end at 13.

7. High-Efficiency Air Filters

As their name suggests, High-Efficiency filters are extremely efficient when it comes to trapping dust and air particles. They are primarily made from an artificial polyester material which is highly effective at trapping pollen, dust particles, mould, residue, and other irritants.

High-Efficiency air filters remove at least 85% of residue swirling around in the atmosphere. They have a MERV rating that sits between 14 and 16.

Which Type of Air Filter Is The Best?

There is no doubt that the air quality of your home is important. However, it is also essential to select a proper filter for your furnace. Filters that have high MERV ratings can end up restricting air flow and causing your heater to malfunction.

Conclusively, we would recommend that you use a filter with a MERV rating that sits between 8 and 14. This should ensure that your HVAC system is adequately protected.

Similarly, you can consult an HVAC expert to help you with making this decision. You don’t want to spend needlessly on filters with high MERV ratings, especially if you don’t need them.

Reusable Filters

If you are looking to protect the environment in your little way, then we would recommend that you buy reusable filters. A considerable number of air filters are disposable. While they may be effective, they are not precisely environmentally forward.

Reusable air filters, on the other hand, can be washed and reused for extended periods.

Reusable air filters are moderately efficient. For most, their MERV ratings fall between 6 and 10. Additionally, you should know that most reusable air filters on the market have hefty price tags. However, since you won’t have to buy a replacement for a long time, it is a price that is cost-effective in the long run.


When buying filters, make sure that you clarify how often they need to be cleaned or changed. Most filters need to be checked and cleaned at least every 90 days. If your filter is dirty and can’t be washed, buy a new one immediately.

Before changing your furnace filters, make sure that you have turned off your furnace. If you don’t know how to do it, there is no shame in reaching out to a professional.

Our professional HVAC contractors are on hand to help you with your every need. Call us today.