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Your Guide to HVAC Filters

Indoor air quality can be improved significantly by replacing HVAC filters. Do you know what type of filter is best for your HVAC system? Read to find out!

Understanding Different Types of HVAC Filters

Usually, HVAC filters come in standard sizes that match most residential and commercial HVAC units.

Before you order any new replacement HVAC filters, double-check the size you need. Usually, you can find the dimensions on the box or manual from the manufacturer. If you need to, get a ruler out and check the old-fashioned way!

Otherwise, contact Sig Cox Heating & Air Conditioning and we can help you determine what you need.

HVAC Filters for Your System

There are many different kinds of air filters. Depending on the minimum efficiency reporting value (MERV) rating, they can range anywhere from $2 to over $100.

You’ll need a custom-sized filter if you have an unusually large or small HVAC unit. Most manufacturers only make standard sizes, though some will create custom ones at higher prices.

Essentially, every building has a unique layout, meaning you can expect all kinds of oddly shaped filters across the market.

How Do HVAC Filters Work?

HVAC filters are sheets of foam and special perforated paper that work by trapping microscopic dust particles. Normally, you slide an HVAC filter under a slot below the furnace unit inside what’s known as the return grille. Your filter serves to keep your system clean by preventing particles from polluting the indoors atmosphere.

However, most filters just block the dust and bacteria, they don’t destroy them. Over time, the screens will become clogged and become hazards themselves by building up an overload of particles.

What Are Standard HVAC Filter Sizes?

While they might vary by the manufacturer, most filters in the industry come in set dimensions measured by inches, including:

  • 10 x 20
  • 12 x 12
  • 12 x 20
  • 12 x 24
  • 12 x 30
  • 12 x 36
  • 14 x 20
  • 14 x 24
  • 14 x 25
  • 14 x 30
  • 15 x 20
  • 16 x 20
  • 16 x 25
  • 18 x 18
  • 18 x 20
  • 18 x 25
  • 18 x 30
  • 20 x 20
  • 20 x 24
  • 20 x 25
  • 20 x 30
  • 24 x 24
  • 25 x 25

What Happens When You Have a Dirty Air Filter?

When a filter is clogged with dirt, it can lower the effectiveness of your system and increase your heating and cooling bill each month. Eventually, the dust will begin to collect on the coils deep within the HVAC system. It’s much more expensive to clean or replace the coils instead of just changing the filter.

Depending on the size of your building, how many people reside in it, and the filter type, you should change your filter every one to three months. Use good judgment and check for clear signs of buildup on the filter.

Scheduling regular HVAC maintenance can also help ensure your air filter is the correct size, clean, and helping your system work effectively.

Need HVAC maintenance or filters in the North Augusta area? Contact Sig Cox today!

What Are the Different Types of HVAC Filters?

There are several types of HVAC filters on the market. Which one you choose for your home is largely dependent on your system and you and your family’s needs. Those who suffer from severe allergies will want to spend a little extra on higher-quality filters, for example.

The amount of purification you want and the quality of air in your home all depends on the type of HVAC filter that you have. Let’s take a look at the various filter types out there.

There are four main types of HVAC air filters—fiberglass, pleated/polyester, electrostatic washable, and HEPA.

1. Fiberglass HVAC Filters

Fiberglass is a term used to describe threaded man-made glass material. For HVAC filters, it’s the cheapest material and has the shortest life span compared to others. They are often called “disposable” filters because experts recommend you trash them after a month.

They are most effective at blocking larger particles, like bugs and dust mites. However, they aren’t very durable. Even with a reinforced metal frame, they won’t last longer than 30 days. Most HVAC filters that you see are made out of fiberglass. Individual strands of fiberglass are spun together to catch particulates that are brought in with the outside air.

Only large particles will be filtered by this type of filter. They will not help keep your home free of smaller airborne matter. These filters are inexpensive, usually anywhere from $2-$10 each, and they can be thrown away without having to think twice about it. For this reason, they will likely continue to be the most common air filter used.

2. Pleated or Polyester

cheap air filters

Pleated/polyester filters are similar to fiberglass ones. However, they have an added wired back for increased durability and ability to capture even smaller particles. Typically, they last up to 90 days. Pleated HVAC air filters cost more than fiberglass HVAC filters, but they are still fairly inexpensive.

So, while they might cost more than their fiberglass counterparts, you’ll save more annually by using them. For an additional level of filtration, some people opt to use pleated air filters. These types of filters are often made out of polyester or similar material. They can eliminate additional particles such as pet dander, dust mites, and other medium-sized particles.

You can remove around 45% of particles from your home’s air with this type of filter. You have the choice of buying reusable or disposable pleated HVAC filters. The reusable ones can just be washed and dried, then put back into the system. Just like with fiberglass HVAC filters, the disposable pleated filters can be thrown out in the trash.

3. Electrostatic Washable

popular air filters

These rely on static electricity to collect the dust, rather than filtered cloth or foam. It’s a relatively expensive option, usually around $30 to $100. 

It’s considered permanent since all you need to do is wash it once a month, rather than replace the whole thing.

Cotton and paper are typically used to make this filter, and there are even disposal electrostatic filters available.

air filters that are washable


HEPA stands for high-efficiency particulate air. HEPA filters are capable of removing the most air particles and are the most efficient commercially available type of filter on the market. With the ability to block and eliminate 99.97% of particles down to 0.3 microns in size, they will guarantee you the cleanest indoor air possible.

These are commonly used in powerful air purifiers for offices, medical labs, and in disaster recovery. They will leave your home free of a variety of contaminants. That includes tobacco smoke and tree pollen. Air is forced through the filter, which is made of aluminum and fibers, and the contaminants are removed during this process.

These are the most expensive of air filters out there, as most quality HEPA filters are over $100. HEPA filters can also be cleaned and reused.

allergy air filters

Where Do You Find Custom Filters?

If none of the above sizes match perfectly, you’ll want to order a custom-made filter to fit your system.

If you attempt to use a filter in the slot that is too small, air will just flow around it and render it useless. On the other hand, if you try to jam in a filter that’s too large, the edges will become crushed in the tight space, and it won’t last very long.

There are plenty of companies that sell air filters of different sizes and materials, both offline and online. There are even companies out there that can design, engineer, and manufacture custom air filters according to your specifications.

You might want to explore companies such as Precision Filtration ProductsFiltertech, or Koch Filter Corporation.

However, you should know that custom filters tend to cost more and may take 5-10 days to manufacture.

Before you commit to investing in a custom air filter, give Sig Cox a call at (706) 962-6980. We can give you the exact measurements you’ll need and recommend the right brand.

HVAC Filters & Maintenance in North Augusta, SC

HVAC filters are the cornerstone of your air handling system, whether it is for your home or business. There are many options so you can get the level of clean air that you need.

Sig Cox Heating & Air Conditioning is here to serve you for all your heating, cooling, and air quality needs. From simple fixes to new installations, we cover it all! We’re open 24/7 to handle any residential or commercial job.

Call us today for a free quote on your needs (706) 962-6980 or contact us online.

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