Many people rely on their air conditioning system to keep their indoor temperatures comfortable when it feels hot outdoors. One of the most underrated and misunderstood components in the AC system is the humble air filter. Some people are unaware that the air filter fulfills a crucial role to protect the sensitive system components from damage. But, the type and quality of the AC filter can have a dramatic effect on your home. In this article, we will take a closer look at AC filters, provide a description of the two most common types, and hopefully, this will help you to make informed decisions.

A Brief Primer on AC Air Filters

Some people believe that the air conditioning system cools their home, but this isn’t true. A better way to describe the process is that the warmth and humidity are removed. The cooling process is almost a side-effect, the AC system removes airborne pollutants and humidity which both lower the indoor air quality (IAQ). The main role of the air filter is to capture pollutants, such as dust, pollen, dander, pet hair, debris, and other contaminants that are circulated in the indoor air. If these contaminants enter the sensitive components of the HVAC system, they can degrade performance and energy efficiency.

There are two main terms that are commonly referred to as acronyms, which can be helpful when trying to understand AC air filters. They are MERV and HEPA. Let’s take a look at these air filter characteristics in more detail:

Minimum Efficiency Reporting Value (MERV)

This is a value that goes from 1 to 20 and higher numbers stop more pollutants from passing through the air filter. To put this into some perspective, a MERV rating of 1-4 would remove particulates up to 10.0 microns in size (pollen, textile fibers, and dust mites). In comparison, a MERV rating of 16-20 would remove particulates from 0.3 up to 1.0 micron in size (bacteria, carcinogens, insecticides, and even sea salt). As you can see, the highest MERV ratings would be overkill for home use and most air filters fall into the 12-16 range. At the 12-16 MERV rating, it is possible to remove a number of harmful airborne pollutants, including pollen, mold spores, dander, some bacteria, tobacco fumes, and more.

High Efficiency Particulate Air (HEPA) Filters

These are air filters that have a dense structure to trap a wider range of potentially harmful airborne pollutants. As you might expect, HEPA filters tend to have higher MERV ratings and they are an ideal choice if you want to improve your IAQ.

The Air Filter Tradeoff

Now that you understand the MERV and HEPA terms, it’s natural to consider using them in your home, but there is a tradeoff to consider. The higher the MERV rating, the better the IAQ, but the airflow is also diminished. The denser structure of these HEPA air filters will require considerable power to force the air through the filter and to maintain airflow. The AC system relies on a steady supply of air to work efficiently and the components can be damaged if the airflow is drastically diminished. Forcing air through a high MERV rated air filter will require a lot of power and this will raise the energy bills. Most residential AC systems cannot use the highest MERV rated air filters which are typically installed in locations, such as surgical rooms, clean rooms, and laboratories. So, it’s important to achieve some balance to protect your AC system, improve the IAQ and prevent damage to the equipment and higher energy bills.

Two AC Common Filter Types Explained

Let’s take a closer look at two common air filter types in more detail. They are:

1.   Washable AC Air Filters

These units can be removed, cleaned, dried, and replaced in the air filter housing. The cleaning process is simple, run the air filter under running water until the dirt and debris are removed and the surface is clean. Then they should be air dried for at least 24 hours to prevent any mold growth on the surface of the filter membrane. It’s not advisable to run the AC system without an air filter, so it’s a good idea to have a pair of these air filters. Then you can use one while the other is cleaned and drying. A washable air filter produces less waste and you will save money because it can be used for a long time. But, these air filters tend to have lower MERV ratings, they don’t remove the same volume of airborne pollutants when compared to replaceable air filter types. This will be an important consideration for homes where smokers, allergy sufferers, pets, and people with pre-existing respiratory conditions reside.

2.   Replaceable AC Air Filters

The disposable AC air filters have higher MERV ratings than the aforementioned washable units. They are a wasteful option, but they are easy to change and you don’t need to dry them for 24 hours before they can be used. They are more expensive to use, but many people prefer the higher IAQ and this is factored into their decision making. There are two main types of replaceable air conditioning air filters for residential use. They are fiberglass and pleated. Let’s take a closer look at them to help you make an informed purchasing decision:

Fiberglass AC Air Filters

These are less expensive than pleated air filters which makes them a cost-effective alternative to washable filters. But, they need to be changed more frequently and over the long-term you may spend more on air filters unless you buy in bulk. Fiberglass air filters can remove larger particles, but people with allergies will still be affected by smaller particle pollutants such as pollen and pet dander.

Pleated AC Air Filters

Pleated air filters are made with paper, but they have a dense structure because the surface is pleated. This increases the surface area with folds that can catch a higher volume of dust and other particulates when compared to traditional air filters. These air filters have higher MERV ratings, the airflow is not obstructed to a great degree and they don’t require frequent changes. When pleated air filters are compared to fiberglass, it’s easy to see that they are superior, but they do cost more.

If you’re concerned about your IAQ, contact your local HVAC specialist for expert help and advice.