Fiberglass Furnace Filters VS Pleated: An In-Depth Comparison

Fiberglass Furnace Filters VS Pleated: A Comparison

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If you are a homeowner with a furnace or an HVAC system, filters are the next thing to find their way on your shopping list. Using a furnace without a filter means a shorter lifespan for the system itself, as there are a lot of contaminants that are sucked into the air ducts by the blower fan, as well as unhealthy air inside your home, as these contaminants will basically recirculate into the air you breathe.

Read Article: Metal Furnace Filters VS Disposable: Which is Better?

Fiberglass and Pleated Furnace Filters Comparison

Flanders/Precisionaire 12x20x1 Fiberglass Furnace Filters in white background
Nordic Pure 16x25x1 MERV 12 Pleated AC Furnace Air Filter in white background
  • Affordable
  • Traps large particle
  • Lightweight
  • Traps small and large particles
  • Affordable in the long run
  • Lasts longer

A Closer Look

Using a furnace with the wrong kind of filter is also a no-go. If the filter has a dense surface, it could cause the blower fan to overload and have to work harder to pull in the amount of air it needs. On the other hand, a filter with a lower MERV rating means its surface isn’t dense enough to trap the contaminant needed to keep the system safe and the air clean.

Fiberglass and pleated filters are two of the most common types of disposable products designed for your furnace. Yet, they are very different from one another. So, which one of them is best suited for your situation?

Defining the Filters

Woman Holding a Quality Air Filter Box

Fiberglass filters are usually an inch thick and are created in a web pattern of spun glass, set up in multiple layers. Usually, the framing is cardboard or metal. These filters work by trapping contaminant particles in the webs, which overlap in a way that refuses entrance of the large particles in the air.

Pleated filters utilize either a synthetic polyester material or cotton, woven into sheets of paper and pleated. The woven fabric then filters out large and small particles of contaminants from the air as it is drawn through the furnace or HVAC system intake.

So, how do these two types of furnace filters compare? Take a look at some of the important aspects of each for a direct comparison.

Fiberglass Filters

Flanders/Precisionaire 12x20x1 Fiberglass Furnace Filters in white background


In terms of MERV rating, or the measure of the ability to filter out even small particles, fiberglass ranks fairly low. They are typically only available with low MERV ratings, meaning they are not capable of filtering out smaller particles. These are usually not suitable if you have asthma, severe allergies, if you have a large family, or if you have a smoker in your home. However, your furnace has specifications, and some require a lower MERV rating to avoid the system working too hard. In those situations, the fiberglass filter might be to your advantage.

Time and Maintenance

Because they are typically weaker, and things like pet hair and dander can actually work to ‘break’ some of the threads of fiberglass, these furnace filters don’t have a lot of longevity. It’s recommended that you replace them every 30 days, which means you have to make sure you have plenty of new filters around to make sure you don’t have to run out to the store. It also increases the amount of labor involved in other types of filters.

Financial Benefits and Concerns

If you’re looking for a solution that saves you money up front, you’re probably going to like the price tag on fiberglass filters. They are beyond reasonable in price, so you barely even notice the change they add to your grocery bill. However, since you have to replace them so often, the cost can add up through the year.

Availability and Variety

Again, when it comes to MERV ratings, fiberglass filters are limited to the lower end of the spectrum, usually only offering choices between a rating of one and four or five. That means they don’t have a lot of options in terms of more efficient filters for smaller particles. However, if you have an unusual or custom filter size that isn’t one of the most common ones, you’ll be more likely to find what you’re looking for in a fiberglass filter, since mass producing a less expensive product, even in alternate sizes, is simple.

Pleated Filters

Nordic Pure 16x25x1 MERV 12 Pleated AC Furnace Air Filter in white background


Pleated filters offer an advantage in this area. First, the pleating means they actually have a greater surface area, which allows for the capture of more contaminants in the same amount of space. In addition, these are offered in a much broader range of MERV ratings, meaning that you can get one that traps the smaller particles, which include the main contaminants responsible for irritating any breathing conditions.

Time and Maintenance

Pleated filters are more durable and last longer. These should be replaced every 90 days unless you have a very large family or special conditions that create excess contaminants in your home, in which case you may have to switch them out a little more frequently. This is also less laborious for you.

Financial Benefits and Concerns

By comparison, pleated filters are a bit more expensive to purchase, mostly because they are higher quality and more durable. While that might seem like a deterrent, consider that you only replace them 1/3 as often as you’re going to have to replace a fiberglass filter. That means that, if they are less than three times the price of a fiberglass filter, you’re saving money in the long run, and that is most likely the case.

Availability and Variety

With pleated filters, you’ll find a wide variety of MERV ratings available. These are made to work with furnaces of any specification in terms of MERV rating, as well as to be more efficient at removing the smaller toxins that often cause allergic reactions. At the same time, you’re less likely to find one of those odd sizes, and in order to do so, you may have to go to a specialty provider, since these are more expensive to manufacture and aren’t widely available in uncommon sizes.


Are you looking to save money or are you looking to buy a filter that can trap as many contaminants as possible? The answer to this question will determine which of these two filter types is more suitable for your furnace system. There are a lot of variables to this equation, especially if you live in a larger home and have a big family.

Pleated filters have a media surface with a greater capacity to trap particles and contaminants, which makes them more suitable for large homes, for houses that are built next to roads (which typically means that a lot more dust gets inside the house), or for people with respiratory problems that can have all sort of attacks triggered by airborne particles. Fiberglass filters, on the other hand, are compatible with basically every type of filter, as one of their main advantages is the fact that they allow greater airflow to pass through their surface. This means that the chances of your furnace system malfunctioning because of a blower fan overheat are reduced.

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