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How Often Should You Change Your Furnace Filter?

Changing furnace filters is an essential home maintenance operation that is sometimes overlooked, which poses a threat of damage to your HVAC system. This means that when you run your heating and cooling system with a dirty filter, you jeopardize your system, comfort, and money.
Most people believe that the furnace filter's duty is to remove impurities from the air in order to produce cleaner indoor air quality. However, although this is one of the functions of the furnace filter, it is only secondary because improving air quality is not the primary function of the furnace filter. The furnace filter eliminates your heating and cooling system's dirt, dust, allergens, and other pollutants. It protects the HVAC system's delicate components by removing airborne contaminants.

How Often Is Changing Furnace Filters Necessary?

The frequency with which furnace filters must be changed varies from house to house. The frequency with which this job must be completed highly depends on the type of furnace filter in use.
Changing furnace filters should be done once a month to once a year - just as there are many different types of filters, so is the frequency with which they should be changed. Fortunately, replacing furnace filters does not need a guess. The recommended replacement frequency is provided by the filter's manufacturer in the product information included when you purchase a new filter.
Size counts when determining how frequently you should change your furnace filters. Because thicker filters contain more media to absorb pollutants, a 5-inch filter requires fewer replacements than a 1-inch filter. Filter efficiency also has an effect, which is recorded as MERV, which stands for minimum efficiency reporting value.
If the size of the furnace filter is considered, then 1- to 2-inch filters are to be replaced every 1 to 3 months: 3- to 4-inch filters are to be replaced every 6 to 9 months: and 5- to 6-inch filters are to be replaced every 9 to 12 months.
While size and efficiency are two important details to consider when replacing furnace filters, there are other factors that need to be considered.

Home Occupancy

The number of people who live in a house influences the life span of a furnace filter. Filters are changed more frequently in large households than in places with only one or two residents. People contribute various contaminants to the home environment; thus, the more people in your house, the more pollutants the filter will have to trap. Presence of Pets in the House Pets are another significant source of pollutants in the indoor air supply. These furry family members shed fur and dander, which the HVAC system picks up and circulates in the home. The useful service life of a filter is reduced by around 30 days for every furry family member residing in your house, so you would need to replace furnace filters more frequently.

Indoor Air Quality

Furnace filters won’t last as long in a home that has poor indoor air quality as they will in a house with acceptable indoor air quality. Indoor air quality devices, such as air purifiers and air cleaners reduce pollutant volume, resulting in fewer particles for your furnace filter to absorb. In houses without this equipment, the furnace filter becomes the sole line of defence against airborne contaminants, so it fills up faster, and as a result, it will need to be changed more often.

Allergic Reactions

Family members who suffer from allergies or asthma can influence the frequency with which you change your furnace filters. This helps to guarantee that toxins causing symptoms are eliminated from your indoor air supply.

Heating & Cooling Usage

Filters have a shorter functional service life when the home's heating and cooling equipment is widely used - air is cycled more often, so the filter has more opportunity to take up contaminants and get blocked.

What Could Happen If Furnace Filters Are Not Changed Regularly?

Various issues happen when regular furnace filter changes are neglected or skipped. Some of these problems include:

Damage to the HVAC System

When the furnace filter is not changed regularly, airborne dust, dirt, and other debris accumulate and worsen the furnace’s performance, even causing damage to components. Also, when filters become clogged yet the HVAC system continues to function, air does not circulate efficiently. Heating and cooling equipment expends more energy to push air forward when a filthy filter blocks its passage. This additional labour strains the system's components, using more energy and causing equipment damage.
Apart from these, a dirty filter restricts airflow and elevates the temperature within the HVAC system, causing it to overheat. After cooling, it restarts, but the problem remains — this is known as short-cycling, and dirty filters are the most typical reason. Short-cycling causes HVAC system damage that necessitates repair and premature total system failure, as well as increased energy consumption, higher utility bills, and decreased interior comfort.

Poor Comfort & Air Quality

Since airflow is hindered when furnace filters are not changed, living spaces do not receive an adequate quantity of heating and cooling. It is difficult to maintain comfort levels, and home occupants frequently notice hot and cold patches. Also, when the filter is clogged, there is no more surface area to absorb new particles as they pass through. As a result, those pollutants linger in the air supply and travel back into your house, causing allergy symptoms, respiratory troubles, body irritations, and dirtier surfaces regardless of how regularly you clean.

How Do You Know The Kind Of Furnace Filter To Buy?

There are several types of filters available. To keep things easy, get the same size filter you currently own. Before you rush out to the hardware shop, take measurements and thickness of your present filter. It would be best if you also wrote down the brand name or snapped a picture of the entire thing to compare at the store. It would help if you also took note of the MERV rating of the filter you want to purchase because the higher the MERV, the higher the efficiency and the better the filter is at trapping particles.


Changing your furnace filter regularly is a simple method to preserve healthy air quality in your house, keep your furnace in excellent working order, and even save money on energy bills.

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