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A Guide to the Different Types of Furnace Filters

March 20, 2023

Did you know that it costs about $4,453 on average to buy a new furnace? On the high end, a furnace replacement might cost homeowners over $6,000.

That's why furnace maintenance is so important and changing air filters should be a top priority. If you're new to furnace care, you might not have a clue which filter options work for your model.

The following guide will explore different types of furnace filters, how they work, and their many benefits.

Understanding HEPA Filters

HEPA stands for high-efficiency particulate air and it can catch up to 99% of pollutants bigger than 0.3 microns. They work well for stopping indoor contaminants and help create a better atmosphere to live in.

Often times homeowners use HEPA filters in air purifiers separate from their furnaces. However, some homeowners incorporate HEPA filters into their HVAC systems.

HEPA filters help purify the air around the furnace so that it's clean. You'll find that some HEPA filters use UV light to destroy living pathogens.

Fiberglass Filters

Fiberglass furnace filters are an affordable alternative to polyester filters. They are safe to dispose of after using them so you don't have to worry about spending extra time cleaning them.

These synthetic filters stop most particles from passing through if they're over 50 microns. They'll even prevent some particles under 10 microns from passing through the filter.

These filters stop dust and dirt from accumulating on crucial parts of your furnace. For example, they help protect heat exchangers and motors from buildup so that they can run efficiently.

Other than trapping big particles to keep your furnace clean, they also improve the system's airflow. However, fiberglass filters won't stop dangerous pollutants that might cause health issues for your household over time.

Polyester Filters

Polyester filters get made from top-quality materials and they typically come in medium sizes for furnaces. These filters stop around 80% to 95% of big particles from passing through.

However, they're much more costly than fiberglass filter alternatives. If you have health issues, they might be worth the extra money because they limit pollutants from entering the home.

Pleated Filters

As the name suggests, these filters get created with pleats making them look like an accordion. Using pleated filters delivers a more generous surface space for filtering out debris.

The pleats generally consist of interwoven cotton or polyester. The weave of fiberglass filters get spread out enough that you can see through them. Pleated filters have a more solid weave to them so they catch more contaminants.

Pleated filters usually have a MERV rating somewhere between 6-12 depending on how tight their weave is. Keep in mind that you'll need to dispose of and replace a pleated filter after 3 months of use.

Filters work harder the higher their MERV rating is. If you go with a very high rating for your filter, expect to change it more frequently.

Washable Filters

You'll find that the most common furnace filters for sale are disposable and generally last about 1 to 3 months. However, there are washable furnace filters that can last up to a decade with proper care if you're willing to spend a lot more money upfront.

Using a washable furnace filter is a nice eco-friendly alternative to disposable options, but they have a lot of disadvantages. For example, washable options usually have much lower MERV ratings that make them less effective.

The greatest MERV rating for most washable filters peaks at around 4. That means that they won't filter out things like mold spores, byproducts from cooking, and hair sprays.

They're a decent choice for filtering out pollen if you or someone in your household suffers from allergies. Just remember that you have to be very delicate with washable filters when you clean them.

You can't let a washable filter dry in a dark and damp space such as a basement or bathroom or it'll develop mold. If that happens, it defeats the purpose of the filter and you'll end up spending more money on a replacement.

If you have the time and patience to take care of a washable filter and don't mind the low MERV rating, it might make a good choice. Just keep in mind that you might end up spending way more money if you don't tend to them which defeats the purpose.

To wash a filter, use soap and water and let the filter dry completely before ever reinstalling it into the furnace.

Electrostatic Filters

Electrostatic furnace filters purify the air with fibers that charge up to draw in particles. They come in both disposable and washable options but you must check your furnace requirements.

Washable versions of these filters have MERV ratings of between 4 and 10. They tend to last much longer than standard filters but they're more expensive.

Carbon Filters

Carbon filters clean the air by using charcoal to trap gasses with high efficiency. Contaminants stick to carbon molecules, a process referred to as adsorption.

If you buy a carbon filter, always ensure that it is activated and has a high carbon content. Once it's activated, it improves the surface size of carbon molecules and boosts their effectiveness.

The more carbon it contains means the more contaminants the filter can attract and catch. Also, go with a thick carbon filter instead of a thin filter so that it takes more time for the air to pass through.

Understanding Types of Furnace Filters

Now you know about the different types of furnace filters available to buy today. To find the right one, consider your budget, desired MERV rating, and if you want a disposable or washable filter.

If you have more questions, you can contact us at FilterTime. We can help set you up with the best filter for your furnace and we offer a 100% refund for 100 days if you're not 100% satisfied. 

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