HVAC & Air Filtration: How to Choose the Right Air Filter

Indoor air quality (or IAQ for short) –  a term that refers to the level of airborne impurities in a home or building’s air supply – is one of the most basic necessities for a healthy and happy home.  To prevent these pollutants from entering the air you breathe and wreaking havoc on your respiratory system, a solid HVAC system is a must, but it’s equally important that said system be outfitted with the right air filtration components.

While HVAC systems themselves could technically be defined as one big air filtration mechanism, our discussion of filtration components in this context refers more specifically to the interchangeable air filters found within those systems. These components and their abilities vary widely from filter to filter and system to system, and it’s important to remember that just because a system is producing temperate air doesn’t mean it’s producing clean air.

In addition to improving air flow,  choosing the right type of air filter for your system (and changing them as needed) can help you avoid the dangers and downfalls of poor indoor air quality. So how do you choose the right filter? Read on! In this article, we’ll go over everything you need to know to choose the perfect air filter for your system, your home and your needs.

How Air Filters Work

While some more obvious contaminants like smoke and dust can be visible to the naked eye, the vast majority of air pollutants are too small to see and thus easy to ignore. Despite their microscopic size, the overall impact of these airborne impurities – which contribute to the spread of deadly disease, chronic illness, hazardous mold, harmful bacteria, etc. –  can be immense.

Typically situated between your system’s return duct & your air handler, air filters work like a sieve that separates clean air from pollutants. As air passes through the filter screen, the filter media (the material the filter is made of) captures all kinds of particulate matter and air pollutants like allergens, dust, pet dander, etc. Certain filters – the specifics of which we’ll get into here shortly – are even capable of removing bacteria and viruses.

These particles captured within the filter media will eventually coagulate and build up over time, prompting the need for regular replacements and/or cleanings in order to prevent said buildup from obstructing air flow, releasing particles back into your home’s air and lowering the overall performance of both your system and your filter.

5 Factors to Consider When Choosing Air Filters

1. Filter Size & System Compatibility

When it comes to choosing the right air filter for your HVAC system, size definitely matters. The wrong size filter won’t fit (let alone work with) your system, period end of story. In addition to size, however, there are certain types of systems that are only (or at least more) compatible with certain types of filters, and vice versa. As such, it’s important to at least know what size filter you need and what types of filters are compatible with your system before you choose one out of the blue.

2. MERV Ratings

MERV ratings (MERV stands for Minimum Efficiency Value Reporting) are a measurement system created by the American Society of Heating,  Refrigeration and Air Conditioning Engineers to denote the overall effectiveness of air filters. Ranging in scale from 1-16, higher MERV ratings mean a greater percentage of pollutant particles being captured by a filter as air passes through it, with filters that have an MERV rating of 16 capturing more than 95% of particles. This metric also indicates what types of particles a filter is capable of capturing. Filters with a MERV rating of 6 or higher can capture things like lint, dust and pollen, while filters with a rating of 8 or higher can capture dust mites and mold spores. On the higher end, filters with MERV ratings of 11 or higher are capable of trapping pet dander, smoke and smog emissions,  while filters with a rating of 13 or higher can catch bacteria and virus carriers.

3. Lifespan & Replacement Frequency

Not all air filters last a standard number of days, and the amount of time they can go before needing changed, cleaned or replaced varies from filter to filter. This is an important factor to consider when choosing the right filter for your system, because it determines how often you’ll be dealing with it moving forward. This frequency can also increase due to external factors like high exposure to air pollutants like smoke, pollen and pets (more on this later), so the filter itself isn’t the only determinant here, but these factors are equally important to consider in this context since they also effect the lifespan of any given filter.

4. Balancing Cost & Performance

More often than not, higher quality means higher costs, and this same principle applies to air filters. In other words, air filters with greater capabilities and higher MERV ratings will usually cost more than the inverse. Depending on how quickly you go through air filters, these costs can start to add up over time, so it’s an important factor to keep in mind. The balance between cost and performance ties back to lifespan and replacement frequent. Lower quality filters may be cheaper in the short term, but if they’re cheaper because they don’t last as long, the increased frequency with which they need to be replaced could end up costing you more in the long run than a higher quality option would.

5. Environmental Impact & Eco-Friendly Options

While this factor is more important to some folks than others, the environmental impact of your air filter is important to be aware of regardless of your attitudes toward sustainability. There are lots of eco-friendly options for air filters, but what exactly does this mean? More often than not, the “eco-friendly” part simply refers to the materials these filters are made out of rather than how they function, but it’s important to be aware of how these materials will effect the overall performance of your system’s filtration. In addition to being safer for the environment, certain eco-friendly air filter options offer additional benefits like longer lifespans and less frequent replacements.

6 Different Types of Air Filters

1. Fiberglass Filters

Also known as spun glass or flat-paneled filters, fiberglass filters are the most inexpensive option when it comes to residential air filters. While they’re popular with many homeowners due to how affordable they are, these filters typically have a MERV rating of 6 or less. This means they filter mostly larger airborne particles like dust, carpet fibers and pollen, which only accounts for around 20% of particles in most air. These filters can also clog easily, which means they need regular maintenance and replacement.

2. Pleated Filters

The filter media in pleated filters is slightly more high grade than that of fiberglass, which is why they’re also slightly more expensive (but typically worth it). Pleated filters get their name from the way the filter media is arranged in folds for greater surface area coverage – the more pleats in a filter, the more effective that filter will be when it comes to capturing airborne contaminants. This increased effectiveness earns pleated filters a higher MERV rating (typically between 8-11) for their ability to trap smaller particles like pet dander and mold spores in addition to larger particles like dust and pollen.

3. HEPA Filters

HEPA filters – HEPA standing for high-efficiency particulate air filters – are aptly named, as they definitely are on the higher end when it comes to their overall efficiency. While certain fumes and gases may be able to pass through undetected, HEPA filters can capture up to 99.7% of airborne pollutants, including viruses, smoke particles and bacteria, earning them super high MERV ratings of 13+. These added benefits come at a very literal cost, however, as they are significantly more expensive than fiberglass and (to a lesser extent) pleated filters.

4. Washable Filters

Available in both flat-paneled and pleated models and often regarded as the most environmentally friendly air filter for their reusability, washable filters offer homeowners a long-lasting alternative to disposable filters. While the base cost for washable filters is higher than that of their disposable counterparts, the recyclability of washable filters will typically save you money in the long run. Unfortunately, most washable filters are only effective against larger particles, resulting in lower efficiency and MERV ratings.

5. Electrostatic Filters

Electrostatic filters feature media materials made from cotton and paper fibers that capture particles via a magnetic reaction to the static electricity these materials generate. These filters are relatively affordable to begin with and even come in reusable options that can help cut down costs even more (as well as cheaper disposable options). The unique downside to these filters is that while they are efficient at capturing smaller particles, they are less effective when it comes to capturing larger particles like mold spores and dust, which makes their MERV ratings highly variable.

6. Media Filters

Often recommended for people in heavily industrial areas and those with immune deficiencies, media filters are made from a pleated paper-like material housed in a metal cabinet. The incredibly high surface area coverage of media filters makes them seven times more effective than standard filters (reflected by their super high 13+ MERV ratings), and even more long lasting, with typical lifespans of around two years. The only downside to media filters is their significantly higher costs, which go up even higher when you consider the fact that they need to be installed by professionals.

Assessing Your Air Quality Needs

Common Indoor Air Pollutants

Being aware of the common indoor air pollutants that are present within a home or building is one of the first steps to determining your specific filtration needs. For example, ground level homes that are surrounded by flowers, foliage and abundant plant life will likely experience an excess of pollen, while a chainsmoker with eighteen cats in a high-rise apartment will have to worry more about things like carcinogens, smog and pet dander.

Specific Air Quality Concerns

Speaking of high-rises and pollen, geographic vulnerabilities like this and other specific air quality concerns, such as pets and smokers, play a big role in determining your specific needs when it comes to choosing an air filter.

Allergies & Health Concerns

Health concerns such as allergies and immune deficiencies are one of the most important factors to consider when selecting an air filter. As mentioned, it’s highly recommended that folks with immune deficiencies invest in high efficiency filters like media filters.

Determining the Right Filter for Your HVAC System

Residential vs. Commercial HVAC Systems

Commercial HVAC systems need multiple much larger filters and are often required to use HEPA filters with high MERV ratings to account for a higher number of inhabitants and external contributing factors like geographic vulnerabilities. Residential HVAC systems and their owners, however, are able to choose their filters based on their own particular needs and wants.

Common HVAC System Configurations & Filter Requirements

While most HVAC systems are built with house filters that are 1” thick with a length and width of anywhere from 12”x12” to 30”x30” (give or take), high end media filters require special housing to accommodate their larger size, which is why they require professional installation. With most residential systems and filters, you can typically find the required filter size located somewhere on the filter housing, if not on the side of your current filter.

Manufacturer Specifications & Recommendations

Some HVAC systems have unique manufacturer specifications and/or recommendations when it comes to the type of air filters they require. When choosing an air filter, it’s important to be aware of and adhere to these specific requirements as much as possible, but also to understand when your air filtration needs may outweigh and take preference over these recommendations, like situations in which health concerns are a significant factor.

Maintaining and Replacing Air Filters

Proper Installation & Handling

With most residential HVAC filters, whether pleated or flat-paneled, disposable or reusable, installation should be a pretty straightforward process as long as you have the right size filter for your system’s housing. You just open the filter housing, pull out the old filter, slide the new one in and close it up. As mentioned, media filters require special installation that is best left to HVAC professionals, so we won’t bother going into details on that.

Filter Maintenance Tips

The biggest tip we can offer when it comes to maintaining your air filter for optimal performance and efficiency is simple: don’t forget about it. Too often people run into bigger issues with system performance that could have been prevented had they simply remembered to change their air filter however many months (or years) earlier. Whether cleaning or replacing your filters, make a habit of doing so on a regular basis and don’t forget about it.

How Often to Change or Clean Your Filter

Unless otherwise indicated, most disposable filters have an effective lifespan of around 1-2 months (give or take) before they should be replaced – same goes for washable filters between cleanings. Keep in mind that a surplus of pollutants from things like pets or environmental factors can reduce this lifespan accordingly and increase the frequency with which you should change your filter. In terms of visible signs, when your filter media is coated in a thick layer of dust and debris, it’s time to swap it out for a new one, or a cleaning. If you’re not going by any other metric, changing or cleaning your filter at least once a month should keep you in the clear.

Additional Air Filtration Solutions

Portable Air Purifiers

Portable air purifiers are a great way to supplement your existing filtration and boost your home’s IAQ. They are especially effective for purifying air in small spaces like single rooms, but they don’t have the range to account for an entire home’s air space. This limited range is to be expected, however, as these units are often compact and relatively inexpensive.

UV Air Purifiers

UV air purifiers (or UV filters) are a great way to add an extra level of defense against germs, mold and bacteria. UV purifiers use short-wave UV light to kill bacteria, viruses and other dangerous microorganisms like mold spores. While pricey, UV purifiers are super effective at ridding your air of disease-causing germs, but they’re virtually useless when it comes to dust, allergens, smoke, fumes, etc.

Whole-House Air Purifiers

Whole-house air purifiers work on the same scale as central AC systems, with a single centralized unit that is responsible for purifying air throughout an entire home. As opposed to the limited range of portable purifiers, whole-home purifiers have the range to account for a significant amount of square footage with a single unit. Despite being rather pricey, whole-home purifiers offer an all encompassing solution to indoor air quality. Not to be mistaken for HVAC systems or AC units, these purifiers don’t effect air temperature and are not a traditional system alternative.

Common Air Filtration Issues

Reduced Airflow & Pressure Drop

One of the most common issues that can stem from your system’s air filter is reduced airflow and the subsequent pressure that occurs as a result. While some believe that high efficiency filters can reduce air flow and pressure automatically by reducing the amount of air that’s able to pass through, the reality is that this 99% of the time these issues are caused by dirty filters with substantial buildup.

Noisy Filters & Whistling Sounds

Another problem that can be caused by dirty air filters is a noisy filter. Often, when filters become clogged enough to restrict air flow, this restricted air flow can produce a high pitched whistling noise. While annoying, this is a relatively minor issue with an easy fix. In either case, the solution is as simple as replacing (or cleaning) your filter.

Air Leaks & Filter Bypass

Another common problem with air filters is air leaks or filter bypass, both of which refer to unfiltered air being able to pass through a leak in your filter. This is typically caused by improperly installed or poorly handled filters in which the filter media has become separated from the filter frame. Similar to the other issues, the easiest solution to filter bypass is simply to replace your damaged filter with a new filter.

Closing Thoughts

If nothing else, remember that air filters are crucial when it comes to maintaining your home’s indoor air quality, and choosing the right air filter for your system is an important decision that has a direct and decisive impact on your home’s IAQ. In addition to choosing the right filter, it’s important to make sure that you keep up with regular maintenance. Even the best air filters money can buy can be rendered useless with enough time and particulate buildup, so it’s important to change or clean your filters on a regular basis in order to prevent this and ensure optimal performance.

Luckily, choosing the right air filter and treating it right will be a synch now that you’ve read this article! If you have any more questions about air filters or need help selecting the right filter for your DE, MD or PA home, the HVAC experts at Maichle’s are here to help. Click the Text Us button at the bottom of the page to message one of our experts or give us a call at (302) 328-4822 to get started now!