What Is A Furnace Filter? 4 Big Reasons You Need To Keep Filters Clean

Heating, Indoor Air Quality

Very few homeowners would be keenly interested in how furnace filters work. Most people would often skim through a furnace buying guide for the heating capacity and price, and skip the information about maintaining the filters altogether. 

But this typically underrated component could do wonders in the efficiency of your heating system, or it could set you back some precious dollars if you neglect them. Worse, it can put your family’s health in jeopardy.

DP what is a furnace filter

What is a furnace filter? Why should you keep a strict watch on how clean your furnace filters are, and what would be the disadvantages if you neglect them?

Read on to find out. 

Why Changing Furnace Filters is All-Important

There are at least four critical drawbacks if you fail to keep your furnace filters clean: damage to HVAC components, reduced comfort and health risks, increased energy consumption, and poor indoor air quality.

How will these impact you and your family?

  1. Expensive repair costs due to equipment damage. A dirty furnace filter cannot protect your furnace from harmful particles that may invade its internal components. Even the slightest damage to critical components can cost you outrageous repair expenses.
  2. Shabby home comfort. A furnace with clogged filters tends to overheat which leads to short-cycling. If your furnace keeps on starting and stopping, it will not regulate the temperature in your home which causes immediate discomfort.
  3. High energy consumption, high electric bill. If you don’t clean your furnace filter, your HVAC system will work harder to regulate the temperature in your home. Longer heating cycles often mean greater energy consumption and higher monthly bills.
  4. Poor indoor air quality leads to illnesses. Dust, dirt, pollen, and pet dander stuck on your furnace filters may be recirculated into your breathing air. This can lead to allergies, asthma, and other respiratory problems.

The primary function of a furnace filter is to filtrate the air from harmful particles that may collect on the internal components of your heating system and compromise its performance. A great byproduct of this particular task of the furnace filter is that it keeps the indoor air quality in good condition by blocking out the pollutants from spreading over your breathing space. 

Clean your furnace filter regularly or replace it depending on the recommended type of filter you decided to use. Thinner 1” filters must be changed every 1 to 3 months while 4”-6” wide filters may be replaced between 6 to 12 months.

How Do Furnace Filters Work?     

As you might have assumed, a furnace filter sifts the air that goes through your heating system. Naturally, it clears a range of contaminants from heated air. 

But what might surprise you is that it is not primarily to keep the indoor air quality of your home clean and safe. It is there to mainly keep your furnace in a good condition and working smoothly.

You also might have heard house air filters and furnace filters terms used interchangeably. Or you may even hear some refer to sifting components to an HVAC system as a “furnace air filter”. 

The truth of the matter is that air filters and furnace filters are two different things. While they both serve to clean the air in your home, the key differences are their location in your heating system, lifespan, filtration level, and cost. 

Admittedly, some types of furnace filters have the added benefit of trapping harmful airborne contaminants or pollutants. This in turn improves air quality as a result. But the furnace filter is there to protect your furnace from sucking in dust, debris, hair, and other particles that might reduce the efficiency of your unit and cause mechanical failure.

So how does the furnace filter work? Its function is as simple as it is elegant.

You can often find the furnace filter inside the blower compartment where cold air enters the furnace. As the air cycles through your home, the ducts, and inside the furnace, the filter picks up dirt, dust, and other pollutants and travels along with it. The air passes through the furnace filter and removes these particles before they get in and through the rest of the system.

An air filter or furnace filter is rated through MERV rating, or Minimum Efficiency Reporting Value, established by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). MERV depicts the efficacy of a filter used in heating and cooling units in trapping airborne pollutants. The higher the MERV rating, the higher its effectiveness. 

A furnace filter with a MERV rating of 1 to 7 can capture 3.0 to 10.0 microns of particles, with equal to or less than 20% to 50% efficiency. If the filter has an 8 to 10 MERV rating, it can catch 3.0 to 10.0 microns of particles with a 70% to 80% success rate. But what’s more, it can trap even smaller particles of  1.0 to 3.0 microns in size with up to 50% effectiveness.

When the furnace filter you chose reaches the MERV rating of 11 to 16, it can then filter the smallest particles with a size of 0.30-1.0 microns, ranging from 20% to 95% as the MERV goes up.

The most superior present-day kind of filter is called a High-efficiency Particulate Air filter or HEPA. This can capture 99.97% of particles in the 0.3-micron range. Obviously, much larger particles are trapped with a similarly high success rate.

Does that mean you should automatically run to a shop and beeline for the HEPA-type filters? You can, but it is best if we review first the various kinds of furnace filters so you can have an informed decision of what is right for your home’s specific needs. 

What are the Different Kinds of Furnace Filters?

Several types of furnace filters exist in the market. Besides varying in shapes and sizes, furnace filters are different in terms of functionality and effectiveness.

You must know what each type does since it will significantly affect your furnace operation and how many years you will be able to use it. 

Moreover, make sure that the furnace filter that you get is the right size for your furnace so that dirt and debris will not escape to your heating system and constrain the airflow. In addition, filters are either disposable or washable.

Let us break down the most common types of furnace filters:

Fiberglass or Synthetic Filters

This is the basic type of filter in a furnace. It is often cheap and disposable. It will do the job of keeping dirt and dust from accumulating on heat exchangers, fan motors, and other surfaces, keeping your system components clean and allowing full airflow. 

The downside of this particular type is that it can only prevent 80% of particles that are fifty microns or larger from entering your furnace. This means that minute particles that can harm your health may continue to circulate in your home. If you are suffering from some kind of allergy or asthma, it is best to consider using a more ultra-fine type of filter. 

Pleated Furnace Filter

Usually made out of polyester, cotton, or paper, this type of filter is an improvement over the fiberglass filter as it is better at trapping particulates. It eliminates 80% to 95% of particles that are at least 50 microns in size. This means that more pollutants are removed from the air circulating inside your home. This would be the best choice for anyone suffering from asthma, allergies, or similar sensitivities.

Electrostatic Filters

The filter’s material is made up of electrostatically charged materials. It can actively attract and hold on to particles as opposed to just trapping particulates as air passes through. 

However, when dust builds up and covers the filter, it becomes insulated and will not be as effective as before in attracting particles. This can be corrected by periodically washing the filter.

HEPA Filter

HEPA is an acronym for High-Efficiency Particulate Air. This type of filter can trap 99% of particles that are at least 0.3 microns in size. This equates to more pollutants being removed from the circulating air, which in turn creates a healthier environment. 

However, because of the smaller space where the air can pass through, it can significantly reduce airflow, requiring more energy to pump air through the system. To use this style filter your homes ductwork needs to be adapted to compensate for the extra restriction caused by this style filter.

How Often Should You Change the Furnace Filter in Your Home?

The answer to this question depends on the structure and size of your house and the kind of filter you are using. As discussed, there are different types of filters and they vary in performance, affecting how often they should be replaced, or simply washed. The range can be from every month to every year. 

It doesn’t mean that you have to guess. Manufacturers of filters include the recommended replacement frequency in the product information when you buy a new filter.

But as a rule of thumb, thinner filters require more changes than a filter with thicker material. For example, a 5-inch filter requires less changes than a 1-inch filter. 

You also have to consider filter efficiency. The more effectively a filter traps particulates, the more frequently you need to replace it or clean it if it is washable.

Generally, the recommended frequencies to change your filters are as follows:

  • One-to-two-inch filters – every 1 to 3 months 
  • Three-to-four-inch filters – every 6 to 9 months
  • Five-to-six-inch filters – every 9 to 12 months

Aside from size and efficiency, other factors can affect how often you need to change filters. 

How many people are living in your home should also be considered. Whether you are caring for a pet or pets that shed furs or coats. If you have additional equipment that purifies the air, this reduces the number of contaminants that your filter needs to eliminate. 

Additionally, if some members of your family suffer from allergies or asthma, it may require you to change filters more frequently to ensure the best air quality.

What are the Dangers of Not Changing Furnace Filters Regularly?

If you overlook changing your furnace filters routinely, you may experience a variety of problems that could have been prevented by simple HVAC maintenance and upkeep.

Damage to HVAC Components

Heating equipment like furnaces contain many sensitive parts. When airborne dust, dirt, and other debris reach various parts of the unit and accumulate because of poor air filtration, the system performance may suffer and even cause harm to components.

If large particles get stuck in these complex parts, your furnace may seem to continue to function just fine until the problem is aggravated. These components may need to be replaced which can cost you financial setback on replacement parts and the labor fee of the technician.

When such repair incidents happen, it will diminish the lifespan of any cooling or heating system significantly. The worst scenario is if you have to prematurely replace your HVAC unit merely because you forgot the humble furnace filter.

Reduced Comfort and Health Risks

When filters are clogged by dirt while the system is running, air will not be able to move freely through the ductwork. The most susceptible to this kind of problem is the blower fan whose function is to move the intake air over the heat exchanger and force heated air through the ducts and into your house. 

This will cause the system to use more energy to push the air inside the system. It may also result in increased temperature of components, causing them to overheat.

Overheating results in the heating system to short cycle. Short cycling means your furnace shuts off before it reaches your desired temperature, and starts up again, still failing to provide you the maximum comfort. In addition, that on again off again causes a great deal of wear and tear on the furnace.

Increased Energy Consumption

A heating system with a dirty furnace filter has to work harder to maintain your preferred temperature in your home. As a consequence, it consumes an unnecessary amount of additional energy.

Additionally, if the clogged filters caused the furnace to overheat and short-cycle, the heating process takes longer without the desired result. Both cases contribute to rising energy consumption and electricity expenses. 

If you have a washable filter, maintaining the cleanliness of your furnace filter will usually only cost you some time, or you can pay a professional to do a thorough cleaning for you. Or, if your choice of furnace filter is the replaceable kind, it will only cost the price of the new filter.

But if you compare the total costs of all these filter upkeep routines, it is still a meager amount compared to the expensive electric bills you have to endure month-on-month just because you have a clogged filter.

Poor Indoor Air Quality

Insufficient cleaning and maintenance of furnace filters directly impact the indoor air quality of your home. Unwanted particles can be recirculated into your breathing air which can cause various health problems.

Because the heating system fails to complete a full cycle due to dirty filters, some areas in your home will have uneven temperatures. The indoor air could also feel muggy and have a stale smell. This can be a perfect breeding ground for mold and mildew that can trigger minor to serious allergies.

Some kids even develop asthma at an early age if exposed to airborne pollutants. The elderly and people with compromised health are in much danger to acquire respiratory problems if they breathe unclean air. 

Don’t hesitate to share this item of information with neighbors and friends who can use some furnace filter maintenance in their respective homes. You may be saving them from a lot of financial and comfort-related problems with just the right advice.

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