An effective, long-lasting HVAC system is critical in Tennessee. As one of the most expensive appliances in your home, preventative maintenance and proper care are essential to getting the most out of your system. One of the easiest and most effective ways to improve your HVAC unit is by regularly replacing your air filter.

The role of an air filter is to remove impurities such as pet dander, dust and even bacteria from circulating through your HVAC system. Filters not only improve the air quality in your home, but also protect your system from damage and premature wear.

To help you master the pros and cons of air filters, we put together this handy guide to help cut out the technical jargon.

What are some different types of air filters?

Air filters come in a variety of shapes and filtering mediums, each with different capabilities and price points.


These filters are typically referred to as “rock filters” or spun-fiberglass filters. Typically these are going to be the most affordable air filter you can buy. Traditional flat-panel filters have a fine mesh of fibers stretched over a framework and bordered with cardboard-like material or thick paper. These filters are cheap and easy to install, but aren’t the highest quality because they allow many particles through.

Pleated Paper

Disposable pleated filters use plastic fibers or a dense weave of cotton to help pull particulates from the air. Unlike their cheaper rock filter cousins, they have pleats (a type of fold formed by doubling fabric back upon itself and securing it in place), which provide more surface area to aid in filtration and allow the filter to catch more debris. Pleated filters are a bit more expensive than flat-panel filters.

Electronic (electrostatic)

This family of air filters are electrostatically charged to trap more, smaller particles such as pollen, smoke or bacteria within their screens. They can be flat or pleated, and they can be washable or disposable.


Washable or reusable filters come in a few different options: ­flat-panel and pleated. The benefit to the filter elements is they are designed to be regularly vacuumed or hosed down with water to remove dirt and debris. They are more eco-friendly than disposable filters, but there is a catch. Reusable filters will lose their electrostatic charge over time, which causes the filter to lose ability to capture smaller particles. So even washable filters have a life span, usually between 3 to 5 years.

High-efficiency particulate air (HEPA)

The title of “HEPA” is assigned to any filter that consistently removes at least 99.97% of airborne particulates 0.3 microns or larger. HEPA is a title endorsed by the United States Department of Energy. These filters are most commonly used in commercial settings that require very clean air (ex. manufacturing facilities, hospitals and laboratories). They can also be used in households where people suffer from allergies or have a compromised immune system. Not all HVAC systems are ­designed to handle these filters, however. We often see HEPA filter elements installed inside furnaces that are NOT designed to handle them, creating too much resistance on air traveling through the system which can cause problems.

What do all the numbers mean?

Air filters are rated for their ability to remove particles from the air. The industry standard for measuring filter performance is the “Minimum Efficiency Reporting Value” (MERV) sale, a rating from 1-12 developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. It designates less filtering mediums with lower numbers and more restrictive mediums with higher values. Some brands have created their own rating systems, such as Home Depot’s Filter Performance Rating and 3M’s Microparticle Performance Rating.

Another rating method is the Clean Air Delivery Rate (CADR), a scale recognized by the Federal Trade Commission and the Environmental Protection Agency that also measures air purifier efficiency. As with MERV, higher numbers equal better overall performance in terms of particle removal. Most filters fall between the 12 CADR and 240 CADR range, though some high-performance ones can go up to 1,200 CADR.

How do I choose the best air filter for my home?

Start by determining the specific needs of the occupants in your home, which should ­directly correlate with the CADR or MERV ratings of your air filters. Filters with a higher CADR rating are the best choice for families who suffer from allergies, have pets in the home, deal with excessive dust or want to capture airborne bacteria. The same concept applies to MERV ratings: Using a more restrictive filter reduces the number of particulates and allergens that end up circulating throughout your home.

But avoid going too far with your filters. Some HVAC systems are not strong enough to push air through more restrictive filters — that is, ones with a higher MERV or CADR rating — which can reduce airflow and cause your home to be heated and cooled less efficiently. Overworking an HVAC system can also lead to hardware damage or an expensive repair. Consult your system’s manual to determine how strong your model is or call an HVAC technician.

Once you’ve narrowed down what rating you need, you can factor in your budget. In general, disposable fiberglass filters are the most affordable, starting at roughly $5, while washable filters start around $9, but they might save you more money over their lifetime.

Finally, you’ll need to consider the dimensions of your ventilation openings and the spaces your HVAC system is servicing, which will determine what filter size and thickness you’ll need. If you are looking to add a different size filter, then you might need to install a separate filter housing or modify your existing ductwork to accommodate for that. Home Depot also has a great filter selection tool.

How do I maintain an air filter?

Proper maintenance of air filters — either replacing or washing them regularly — is crucial not only to providing clean air in your home, but also to keeping your HVAC system functioning properly. Maintaining your air filter shouldn’t be a huge task. Most filters are easy to insert or swap out, and it’s one of the few things you can do without the help of a trained specialist.

Although you should check the instructions for both your HVAC system and your specific filter for maintenance guidelines, you typically should change filters at least every season, if not monthly. Even a high-quality filter can’t do its job right if it’s clogged with debris. If you live in a brand new home or have remodeling or construction taking place, you’ll need to change your air filter more frequently to compensate for the extra dust in the air.

We suggest that you write the date you changed your filter on its spine so you can keep track of your maintenance schedule. Or, thanks to today’s smart-home technology, you can even buy smart filters such as 3M’s Filtrete Smart Air Filters that use sensors to monitor air flow. Such filters will send an alert to a mobile app to let you know when you need to change it.

If any of this sounds too confusing or if you need some professional advice, please reach out to our office and we’ll be glad to lend a hand. Tom’s contact information is HERE.