Does Air Filter Sizes Matter

Air filters are silently protecting you and your family 24 hours a day, seven days a week. They do the dirty job none of your other appliances are willing to help with, improving indoor air quality. With an improperly fitting filter, there's a high chance that your lungs are getting clogged with dust particles and allergens flying freely in the air.

As you delve deeper into the world of air filtration and its effects on indoor air quality, you'll find air filter size is a choice that impacts more than just the air you breathe. Air filters are an essential part of any home and this article highlights why the size of your air filters matter, how to find the right size for your home, the answer to the question "Does air filter size matter," and some considerations to keep in mind for the wrong sized filter.

Why Air Filter Sizes Matter

The reason your home has air filters is to trap pollutants and allergens, preventing them from circulating throughout your home. This is especially true for people with pets who battle every day to keep their hair in control.

While most homeowners can agree that filters help to keep indoor air clean, very few consider the exact sizes of their air filters. Even less think about the consequences of using the wrong size.

Just like a suit tailored to your measurements, an air filter needs to be the correct size in order to function efficiently and effectively.

The qualities that matter most in an air filter are its size, material, and MERV rating. The MERV (Minimum Efficiency Reporting Value) rating measures how effective the filter is at trapping small particles. A higher MERV rating means better filtration but also more resistance to airflow. So, balance is key.

Finding Your Air Filter Size

Finding the right air filter size is simple even if you don't have previous experience. There are two main ways to check for the exact dimensions so you can get a proper replacement.

Check the Existing Filter

The easiest way for anyone to find the air filter size is to check the existing filter. Most manufacturers will add the exact dimensions of the filter on one of the sides.

You'll see it written as "20x20x1" where the first two numbers represent the length and width, while the last number represents the depth or thickness.

Here are some steps to follow so you stay safe while looking at your filter:

Turn off your HVAC system: Before you get started, turn off your heating and cooling system to avoid any accidents.
Locate and remove the existing filter: The filter is usually located in the return air duct or blower compartment before the return air reaches the air handler. You can access it by removing the service door or panel. Once you've found it, carefully slide it out of its slot.
Check for filter size: Most air filters will have their dimensions printed on the frame of the filter, which includes the length, width, and depth.
Reinstall existing filter: If you're not replacing the filter immediately, slide it back into its slot and replace the service door or panel. Otherwise, dispose of the old filter according to your local waste disposal guidelines.

Use Online Size Selectors

Online size selectors are tools that help you find the right air filter size by inputting your HVAC system's make and model. They provide you with a list of compatible filters that fit your system.

Apart from the dimensions, these tools also consider features like MERV rating and material types so you can easily compare and choose the most suitable option for your home.

The tools are usually located on manufacturer's websites where you can set up a subscription or reordering service. Using an online size selector removes the guesswork from the equation and gives you the exact dimensions for your unit.

How to Measure Your Air Filter

If you're buying a home air filter for the first time or don't have the old filter you can use an old-fashioned method of measuring the filter using a tape measure.

Measure the length and width and depth and log down your numbers in that order. You'll probably get a very specific number like 15 3/4 or 19 1/2 which is okay. Remember to always round up to the nearest inch because manufacturers only print the nominal numbers to make it easier for homeowners.

Next, double-check with your manufacturer's recommendations for your specific HVAC system. They often provide guidance on the appropriate filter sizes, types, and replacement frequency.

When you've triple-checked your measurements you can feel confident moving forward with the right filter for your home.

Nominal Vs. Actual Filter Sizes

Air filter sizes can be a bit perplexing if you're not familiar with the lingo. You see, there are two measurements to consider: the nominal size and the actual size.

The nominal size is the rounded-up number that manufacturers use to label their products. It's essentially the "nickname" of the air filter size. So, a filter that measures 19.5x24.5x0.75 inches would have a nominal size of 20x25x1. This makes things simpler when you're shopping for a new filter.

On the other hand, the actual size is the precise measurement of the filter. These are the exact dimensions — length, width, and depth — of your filter.

You only need to remember that filters are always rounded up to nominal sizes at stores, so the next time you're buying a filter you won't waste time by purchasing the wrong one.

What Happens if You Use the Wrong Size Air Filter?

When an air filter is too big it won't fit into the slot. You might be tempted to force it in, but this could damage both the filter and your HVAC system. Altering the filter isn't recommended because it could release particles into the air you'll end up breathing in.

But, if the filter is too small it can't properly seal the duct. This means that unfiltered air bypasses the filter and flows directly into your HVAC system and out into your home.

Not only does this defeat the purpose of having an air filter, but it can also lead to dirt accumulation in your system, causing damage over time.

So, what can you do if you've bought the wrong size filter? Your only option is to return the filter and purchase a new one of the correct size. Most retailers understand the confusion around air filter sizes and will allow exchanges or refunds.

Is It OK To Use a Smaller Air Filter?

Imagine you're trying to strain pasta through a small sieve. It doesn't quite cover the pot, so some of the pasta escapes into the sink. This is essentially what happens with a smaller air filter. It can't fully cover the duct, so unfiltered air flows freely throughout your home.

These airborne particles can trigger allergies, cause respiratory problems, and degrade your home's overall indoor air quality. If you've ever wondered why your house seems dusty even after you've just cleaned it, a small air filter could be the culprit.

Always ensure you're using the correct filter size. Not only will it keep your air cleaner, but it will also protect your HVAC system from unnecessary damage.

Choosing the Right Air Filter

Choosing the right air filter does much more than just clean your air. A filter that fits properly guards against unwanted particles infiltrating your home, maintaining high indoor air quality, and ensuring the health and comfort of your family. It's not just a purchase; it's a commitment to your home's air quality and the longevity of your HVAC system.