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Are Furnace Filters Made of Fiberglass?

The air quality of your home depends on the type of air filter in your furnace. A furnace filter prevents hair, dust, pollen, and other pollutants from reaching the blower fan. Air filters are typically made of fiberglass, but does this apply to all furnace filters?

Some furnace filters are made of fiberglass, but not all. Fiberglass furnace filters are very popular, but they’re not the only type. A furnace filter can also be made of cotton, polyester, and other synthetic fibers. There are also carbon filters that use charcoal to improve the air quality.

This article will explore different materials used to make furnace filters to see how they stack up against one another. Read on to learn everything you need to know about fiberglass furnace filters.

What Are Furnace Filters Made Of?

Homeowners don’t always know where to begin when it’s time to select an air filter. Since there are multiple types readily available in stores, it’s easy to base a purchasing decision on price alone. But what is your furnace filter made of? 

Furnace filters are made of various materials such as fiberglass and polyester. The type of material impacts how effective the furnace filter is. There are also self-charging electrostatic filters that can catch tiny particles and carbon filters that absorb impurities in the air.

The indoor air quality at home depends on the filters of a furnace. Moreover, furnace filters protect your furnace from getting dirty by removing unwanted particles from the air. 

HVAC systems aren’t really designed to help improve air quality in your home, but the filters play an important role in keeping the furnace working properly. Cheap fiberglass filters stop dust and debris from gunking the system. 

Although they can remove some irritants and allergens, that’s not their primary objective. The only exception is pleated filters.

Disposable pleated air filters made from polyester and cotton paper remove small particles such as spores and mites from the air. But the trade-off for fresh air is performance. These filters add resistance to airflow, which leads to increased power consumption.

Moreover, pleated filters can cause stress on the blower’s motor. This impacts the refrigeration in the evaporator coil and can cause the coil to ice up. They also cost more than fiberglass furnace filters.

Although pleated filters can clean the air better than fiberglass filters, there are superior options for filtering your air without stressing your HVAC. For example, you can use electronic air cleaners and UV systems to keep the air in your house fresh.

Whether you go for fiberglass or opt for pleated ones, you need to change your furnace filter regularly. A clean filter won’t force your furnace to operate at 100%, thereby saving you money on the energy bills and prolonging the furnace’s lifespan.

However, filters with a higher rating limit airflow, forcing the furnace to work harder. The United States Environmental Protection Agency recommends furnace filters with a MERV rating between 7–13 for most homes.

To determine the best furnace filter, you must know the minimum efficiency reporting value rating (MERV). The MERV rating determines the efficiency of your air filter. With a rating of 1 to 16, the higher the rating, the more particles it can get rid of.

Types of Furnace Filters

There are several different types of furnace filters besides fiberglass filters. Let’s go over all of them to help you make an educated purchase decision for your furnace.

Pleated Filters

The most common furnace filters in the market are the disposable pleated kind. You can find them in various ratings and sizes. They’re made of cotton paper sheets or polyester. Thanks to a MERV rating ranging between 6–13, they’re highly efficient at trapping particles. 

They can even trap particles as small as bacteria and viruses.

Pleated air filters can last a long time. You don’t have to replace them as often as some other types, allowing you to save on costs.

Fiberglass/Synthetic Filters

Fiberglass filters are the most inexpensive in the market. They typically have a MERV rating between 1–4. Fiberglass filters can capture up to 80% of large particles above 50 microns and 25% of smaller particles. The filters allow for maximum airflow, putting less strain on your furnace as a result.

You need to replace fiberglass filters every 30 days. Moreover, since fiberglass is designed to deal with large particles, it’s less effective at getting rid of small particles. Therefore, the amount of filtering it provides for your HVAC is minimal. So, it does little to protect your body from allergens and other airborne contaminants.

If you have asthma or allergies, keep clear of fiberglass filters. You need a more advanced filtration system.

Electrostatic Filters

These filters are made of self-charging electrostatic cotton or paper fibers. With an average MERV rating of 10, they’re the best air filter for trapping small particles. 

Electrostatic filters work by charging particles and pulling them in like a magnet. They’re either disposable or washable. Disposable electrostatic filters are pleated, whereas washable electrostatic filters are made from polypropylene. 

Washable electrostatic filters come in multiple layers that you need to separate before cleaning. 

Don’t clean the filter with high-pressure water to avoid damaging the filter. Also, don’t postpone cleaning the filter, even if you don’t see any notable dirt on the outside. There are always invisible particles in and around the filter.

Carbon Filters 

If you’re searching for a carbon air filter to get rid of odors and harmful gases at home, you’ve come to the right place.

Activated carbon comes with special properties that allow it to sieve out volatile organic compounds and other gaseous pollutants from the air. The device accomplishes this differently from the other air purifiers such as HEPA, which specifically filter pollutants from the air.

Carbon air filters are designed to trap gas molecules on charcoal, a viable process with a colorful history.

Final Thoughts

Furnace filters can be made of fiberglass, cotton, polyester, and similar materials. They can also be electrostatic or have charcoal to improve their effectiveness. If you’re concerned about the performance of your HVAC, it’s best to opt for fiberglass filters.

But if you want a filter that can remove most impurities in your home, you really want to use pleated filters. Their only major drawback is that they make your HVAC less efficient due to the stronger filtering.

There are several hybrid air purifiers that come with a carbon filter and a mechanical filter such as HEPA. 


  • Steve Rajeckas

    Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

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