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Pleated Filter or Fiberglass Filter? Which is Better for Your Home?

Aug 26th, 2019

by Alec Lower

Are those thin green filters worth using for the extra couple of dollars you can save, or are pleated air filters the way to go?

Pleated Filter or Fiberglass Filter? Which is Better for Your Home?

Are those thin green filters worth using for the extra couple of dollars you can save, or are pleated air filters the way to go?

by Alec Lower

There is a saying in the industry of, well, just about everything that “you get what you pay for.” In the air filter industry, this is as true as it ever was. The two most common types of air filters are fiberglass air filters and pleated air filters and they couldn’t really be more different as far as home air filters go.

What is the difference between pleated and fiberglass?

_fiberglass air filter

Fiberglass

  • Loosely wound/porous
  • Flat
  • Very cheap
  • Provides less resistance to pollutants












pleated air filter

Pleated

  • More tightly wound/less porous
  • Material is folded like an accordion to maximize surface area
  • A little more expensive
  • Provides more resistance to pollutants





So which one of these varieties is better for your home? Well given that we just said “you get what you pay for”, you can probably guess that the pleated ones are better. You would be correct. There used to be some advantages to the cheaper fiberglass, but there really isn’t anymore. Read on to learn more.

Do fiberglass filters get better airflow?

An effective air filter blends filtering efficiency with airflow to create a product that is effective at removing particles from the air but doesn’t create an unnecessary demand on your HVAC motor by blocking air from getting through. Creating a filter like this has been a challenging task because generally speaking, the more efficient a filter is at actual filtration, the worse its airflow is.

Fiberglass filters fall on the far end on that spectrum, delivering near-maximum airflow in a tradeoff that affords almost zero filtering efficiency. There’s a reason they’re commonly referred to as “rock catchers” in the industry. They don’t really filter anything beyond the largest of particles.

That’s not to say that airflow and efficiency are exactly inversely proportional, especially not in 2019. You see, the fiberglass air filter hasn’t changed much over the years. The pleated air filter and the HVAC system have though, and their innovations have shattered the seamlessness of the efficiency/airflow spectrum and rendered fiberglass air filters essentially obsolete.

Pleated air filters used to be the cause of many HVAC breakdowns, because the system motor would have to work harder than it could handle to pull the air it needed through the tightly wound filter. This was years ago when pleated filters were made of cotton and HVAC motors weren’t anything special. A lot has changed.

Pleated air filters are now constructed with synthetic materials that have smaller individual fibers, which are wound in such a way as to maximize airflow and filtering efficiency.

The biggest factor though has been the innovations in the HVAC systems themselves. Puron’s replacement of Freon, along with some general improvements in HVAC construction, have decreased the demands of the HVAC system and made the decreased airflow from pleated filter use sufficient for the system to run smoothly.

SN Tip: Refrigerant cools your home by absorbing heat from the air, thus cooling it down. Puron does this with less energy, because it is more dense. Denser gases absorb energy with less effort, resulting in a quicker cooling process of your home and less demand on the motor. Science!

So the answer to the question is technically yes, fiberglass filters do allow for better airflow, but the difference is largely immaterial to the HVAC system and its health and efficiency. When you factor in everything else we're about to talk about, well, you'll see in a second.

Are pleated filters that much more efficient?

The primary role of an air filter is to pull air pollutants from the air inside your home as it is pulled into the HVAC system. This is a role in which the pleated air filter succeeds and the fiberglass air filter fails with a capital F.

As stated above, fiberglass air filters are commonly referred to as “rock-catchers” because of their abysmal ability to, you know, actually filter stuff. These guys filter less than 25% of particles in the 3 to 10-micron range out of your air. Particles in that range include things like pollen, dander, and some bacteria. These are the primary pollutants that lower your indoor air quality, and three-quarters of them are not being removed by fiberglass. For reference, a pleated filter of only a MERV 8 rating filters out at least 75% of particles between 3 and 10 microns. It’s not even close.

Pleated filters, especially those of a higher MERV rating, are effective against even the smallest particles. A MERV 13 Catch All filter from Second Nature will catch at least 50% of particles from 0.3-1 microns in diameter. This includes tiny little things such as pet dander and iddy-biddy smoke particles. Fiberglass filters are so efficient with particles this small that their percentage is pretty close to zero.

Which one is safer for my system?

Here is where perhaps the greatest misconceptions around air filters can be found. The story goes something like this:

Pleated filters are bad for your system because they block too much air, forcing the HVAC motor to work harder to pull in the air it needs and burning it out faster.

While the airflow advantages that the fiberglass filter once enjoyed have basically been innovated out of style, there’s another element to system health that isn’t as commonly discussed, and fiberglass is outdone by pleated once again here.

When particles pass through your fiberglass air filter and enter your system, one of two things happens. A decent amount of those pollutants cycle back through the system into your home so that you breathe them in. The rest can attach to the refrigerant coils. This is extremely bad.

As your multi-thousand dollar HVAC system gets coated in junk, the evaporator coils are not able to absorb enough heat and the refrigerant operates at a much cooler temperature than is safe. For starters, this drastically lowers efficiency and drives up power bills, because the system has to work so much harder to actually condition your air. Second, this causes water vapor to freeze on the coils, which can lead to catastrophic breakdowns. When people talk about their A/C “freezing up”, this is what is happening.

Pleated filters and their effective filtering work against this issue by minimizing the number of pollutants that can attach to your evaporator coils, while garbage filters that let just about anything through leave you susceptible to it.

Are fiberglass filters cheaper?

The filters themselves are cheaper, but the cost of using them is not much cheaper, and an HVAC breakdown caused by a fiberglass filter twiddling its thumbs while huge particles pass right through is definitely not cheaper.

Most fiberglass filters are around one or two dollars. Pleated are more like 12 dollars, which according to basic subtraction, is more than two. The first caveat here is that fiberglass is only rated to last one month, while pleated filters are typically rated to last three times that long. So while they’re still cheaper, they’re not as much cheaper as you’d think with a one-to-one comparison.

This, of course, excludes the possibility of an HVAC breakdown caused by a buildup of crud on the unit. HVAC repairs are expensive and HVAC replacements are super crazy insane expensive. A shortened lifespan of an HVAC system that results from using such a useless filter will end up costing you way more in the long run than the extra six dollars every three months to buy a pleated one.

Why does my tech recommend fiberglass then?

Despite all of this, many HVAC technicians still recommend fiberglass filters for airflow reasons. Why is that?

The answer is quite simple. Homeowners don’t remember to change their air filter. It’s an epidemic within the HVAC industry and the simplest way for a tech to deal with this problem is to recommend an air filter that won’t catch enough pollutants to create a blockage in your system when it’s never changed.

In situations where modern pleated air filters cause damage to modern HVAC systems, it is usually a result of the filter not being changed. Pollutants will build up on the filter and if it’s left for too long, it will eventually create enough blockage to overwork the system. This is an easy problem to avoid. You just need to change your air filter on a regular basis.

But how in the world can you remember to change your air filter on time when there are so many other things on your to-do list? How???

Turns out you’re on a website right now where you can sign up for a subscription service that delivers filters automatically on your schedule. And they’re pleated!

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In the modern age of air filtration, pleated filters outdo their fiberglass counterparts in just about every category. They’re far more efficient, they’re safer for your air and your HVAC unit, and they’re not significantly more expensive. The choice is clear.

Alec Lower
Alec Lower
Social Media and Content Specialist
After graduating from NC State, I joined Second Nature in the summer of 2018. I have always loved writing and enjoy blogging on subjects that are important to families and homeowners. Outside of work, I love to fish and am a huge college sports fan.