How to Change Your HVAC Furnance Filter

June 01, 2015

Regular maintenance of your heating, ventilation, and air conditioning (HVAC) system will improve its operation and extend its life. It will also help you regulate temperatures in your house—and save you money.

One of the most important ways to maintain an HVAC unit is to change the system’s air filter. Debris and pollutants can harm the system, and the air filter prevents them from entering it. In the process of keeping debris out of the system, the filter begins to fill up, and a dirty filter will slow down air flow to the system, requiring the unit to work harder to heat your home in the winter and cool it in the summer—resulting in increased energy bills, along with unnecessary wear and tear on the system.


Types of Air Filters 

There are four types of air filters for HVAC systems:

  • Fiberglass. This is the most common type of air filter. These disposable filters are composed of layers of fiberglass laid over one another and supported by a metal grating. The fiberglass is what filters debris and pollutants.
  • Polyester and Pleated. These are similar to the fiberglass option, but they provide higher resistance to airflow and superior filtering.
  • High Efficiency Particulate Arrestance (HEPA). These filter air through a very fine scale. The U.S. Department of Energy requires that they filter 99.7 percent of all particles that are .3 micros or larger.
  • Washable. These are most often used in industrial settings. They are made up of cloth and require the build-up of dust along the cloth to actually improve the filter’s efficiency. As the name implies, they are washable.



Depending on the type of filter, you should plan to change it every one to three months. The frequency with which you change it depends on the weather where you live and the intensity or mildness of a particular season. For example, if you’re enduring a particularly hot summer and running your AC on high for an extended period of time, you’ll need to change the filter more often.


How to Do It 

  1. Locate the air filter. They are most often in a slot on the side of the system, but they can also be located in a grille on the wall or ceiling, or the inside blower compartment of the furnace.
  3. Identify the type and size of filter you need. Check the HVAC owner’s manual to confirm the recommended filter type and size. Filters come in different sizes, and you need to make sure you buy the right size for your system.
  5. Buy new filters. Just be sure to buy the right type and size.
  7. Turn off the unit. This is a safety measure. Identify the on/off switch in the owner’s manual, or turn off the breaker for the HVAC unit in your circuit breaker.
  9. Remove the old filter. Simply pull the filter out of its place in the unit.
  11. Install the new filter. Arrows on the filter indicate which side should face outside the system. Slide the filter into its place in the unit with those arrows facing the correct direction.


Even if you’re planning to change the air filter regularly, if you are using your HVAC more than usual, check it for the build up of dust and debris. If you see that it’s getting clogged, go ahead and change it. A new air filter costs less than the increase in energy bills that an inefficient system can cause.

It is important that your HVAC equipment performs efficiently. Apart from air filter maintenance, consider an upgrade or replacement on units more than 12 years old to help you cut long-term costs.

Your HVAC unit uses more energy than any other appliance in your house. Changing its air filter regularly will maximize its efficiency and decrease your energy costs. To learn how to get even more out of your HVAC unit, read the articles "Benefits of a Programmable Thermostat," and “Ways to Optimize Air Flow".

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