How to Choose the Right Furnace Filter

Furnace filters are among the most overlooked components of heating units, but are one of the most essential in regards to performance, efficiency, health and overall home comfort. Originally designed to protect the parts within the furnace, today’s filters can help you save money and improve the quality of indoor air. By knowing the difference between the options available, you’ll select the type that’s best for your home and specific needs.

The Importance of Furnace Filters 

Appliance Longevity

To understand why furnace filters are important, you must understand their purpose. In a traditional forced-air furnace, the appliance draws air through the return ducts in a home. A heat exchanger warms the air before a blower fan pushes it out into various rooms in a home. The furnace continues this cycle until the thermostat senses that the home is the desired temperature.

As a furnace draws in air, it passes through a filter before reaching the blower fan and other components. This protects the fan from contaminants, such as dust, pollen, hair and other particles. When particles build up on the fan, it can become imbalanced. The weight of the contaminants causes the fan and other components to work harder, increasing wear and tear, as well as energy use. Similarly, when dust and contaminants build up on the filter, it becomes more difficult for the appliance to draw in air, which also increases energy use and wear and tear.

Changing furnace filters once a month prevents breakdowns, reduces maintenance costs, saves energy and extends the unit’s life.

Indoor Air Pollution Control

When air passed through a furnace filter, it helps reduce the number of contaminants that circulate in a home. The U.S. Environmental Protection Agency states that indoor air “can be more seriously polluted” than the air outside. Since many individuals spend up to 90 percent of their lives indoors, it’s crucial to take steps to promote a healthy environment.

It is important to keep in mind that while a furnace filter prevents the recirculation of contaminants, it does not “clean” the air. Air purification systems serve this purpose.

Types of Furnace Filters

MERV Ratings

Furnace filters have minimum efficiency reporting values, or MERV ratings, that range from 1 to 16. Filters with higher MERV ratings remove more particles from the air. While it may seem as if filters with higher MERV ratings are better, they may force a furnace to work harder to draw in air. In general, MERV ratings between 8 and 11 are ideal. However, it is best to follow the manufacturer’s recommendations regarding the best MERV ratings for your furnace’s filter.

Common Residential Furnace Filter Types

• Disposable fiberglass: The most common type of furnace filter, disposable fiberglass filters look like white batting within a cardboard frame. The affordable filter has spun fiberglass that’s 1 inch thick, making it effective at removing lint, dust and larger debris. Because it has a MERV rating of 2 or 3, it is good for those who do not have asthma or allergy problems.
• Disposable pleated: A popular option, disposable pleated filters are also affordable. They appear similar to honeycomb blinds and use cotton or polyester paper. This type of filter has an average MERV rating of 6. Its paper is effective at removing small particles, such as mites and mold spores, but could add resistance to a furnace’s air flow. You may need to change a pleated filter more often than a fiberglass filter.
• Disposable electrostatic: Made of self-charging electrostatic paper fibers or cotton, disposable electrostatic filters are good at attracting and trapping small particles. Thanks to their average MERV rating of 10, they are good for homes with pets, children or smokers. While they cost a bit more than pleated or fiberglass filters, they are affordable in standard sizes. Ensure that it is safe to use any type of electrostatic filter in your furnace before installing one.
• Permanent electrostatic: Permanent electrostatic filters work similarly as their disposable counterparts. The main difference is that you can remove and wash the filter for up to eight years. It is also possible to make your own using kits available in stores or online. Because the filter needs time to dry well after washing it, some homeowners purchase two and alternate between them.

It is a good idea to replace a furnace filter once a month. To maintain optimal conditions in your home, you may need to replace it more often during the coldest months of the year or if indoor air pollution is higher. Situations that could increase levels of indoor air pollution include home remodels or renovations, smoking, multiple pets or having a large number of houseplants. If you aren’t sure which furnace filters are best for your appliance, schedule a maintenance service from AAA Heating and Cooling and receive expert advice from our pros.