Air Filters 101: What Every Homeowner Needs to Know

Introduction to Air Filters

Hey there, I’m Brandon, an HVAC service tech, and founder of FilterSender.com and I can’t tell you how many times I’ve gone on a service call caused by homeowners neglecting one of the easiest and most important maintenance tasks—changing their air filter. I hate these service calls because such a simple, yet easily forgotten maintenance task for a homeowner is costing them extra money and damage to their HVAC system. Your air filter does more than just clean the air you breathe; in fact that's not its main purpose. It's a crucial part of keeping your HVAC system running smoothly and efficiently. When your air filter gets clogged it can cause all sorts of issues, from higher energy bills to costly furnace repairs. Let’s break down everything you need to know about air filters and why keeping yours fresh is a must for your home’s comfort and your HVAC system’s efficiency as well as its longevity.

What does you air filter do and Why Does it Matter?

An air filter traps dust, pet dander, pollen, and other airborne particles before they can enter your system. If your filter is clean, air flows freely, keeping your system working with ease and efficiency. But when it gets clogged, your furnace or AC has to work overtime to push air through, leading to breakdowns, higher energy bills, and poor indoor air quality.

The Different Types of Air Filters

Not all air filters are created equal. Here’s a quick rundown of the most common types:

1. Fiberglass Filters – These are the cheapest and most basic, but they don’t do much beyond catching large debris. If you want better air quality, this isn’t your best bet. However they are the best for your HVAC system. They restrict airflow the least.

2. Pleated Filters – In my experience working as an HVAC tech, these are the most common type of air filters that customers own. They do a better job of trapping smaller particles like pet dander and dust mites, making them a solid choice for most homes. They bring a good mixture of efficiency and air filtration.

3. HEPA Filters – If you or someone in your home has allergies, HEPA filters can be a game changer. They capture almost all airborne particles but may require HVAC modifications due to their thickness.

4. Electrostatic Filters – These use static electricity to grab particles from the air. They come in disposable and washable versions and are great for homes with pets or smokers.

5. Carbon Filters – Need to get rid of odors? Carbon filters absorb smells and harmful gases, making your home smell fresher while also filtering out contaminants.

Why MERV Ratings Matter

Every air filter has a Minimum Efficiency Reporting Value (MERV) rating, which tells you how well it traps particles. The higher you go the more you restrict the airflow to your HVAC system, the harder the filter is on your HVAC system, reducing the lifespan of your components and your system as a whole. The effect of having a filter rated too high for your HVAC system is amplified if you consistently forget to change your filter on time. Here’s what you need to know:

• MERV 1-4: Basic protection, mostly good for large particles like dust and lint.

• MERV 5-8: Standard for most homes—captures mold spores, pet dander, and dust mites. Most homeowners do not need to go above a MERV 8 rating. Higher ratings just cost more and restrict your HVAC system, costing much more in the long run.

• MERV 9-12: Higher filtration, great for people with allergies or respiratory issues.

• MERV 13-16: Superior filtration, trapping even bacteria and smoke particles.

• MERV 17+: Used in hospitals—not typically necessary for residential systems and may restrict airflow too much.

Why Changing Your Air Filter is Critical for Your HVAC System

I’ve seen too many homeowners deal with expensive repairs simply because they forgot to or chose not to change their air filter. Even if it doesn’t cause enough damage for a repair, Is it really worth a service call fee for one of us techs to come to your house and simply pull your air filter out. Here’s some average service call numbers in case this helps. https://www.angi.com/articles/how-much-hvac-repair-cost.htm 

 Here’s what happens when you neglect it:

• Restricted Airflow: A clogged filter makes your furnace or AC work harder, which drives up your energy bill and shortens the system’s lifespan.

• Overheating and System Failures: Your HVAC system depends on proper airflow to regulate temperature. A dirty filter can cause your furnace to overheat and shut down. Causing every component of your furnace to overheat as well. If your filter is consistently dirty and your furnace overheats often, in gas and oil furnaces your heat exchanger will crack. Your heat exchanger has to be completely sealed because that is where the CO2 that is produced from operating your furnace goes and is sent out of your house through your flue pipe, either to your chimney or straight outside. When there is a crack CO2 would then travel through your duct work filling your house with ease. So when an HVAC tech such as myself comes to your house and finds a crack in your heat exchanger we are required by law to shut down your furnace. Until you either replace your heat exchanger or furnace. What sounds cheaper and easier, replacing your air filter on time or a new furnace?

• Blower Motor Damage: If your filter is clogged, dust and debris can settle in your blower motor, leading to costly repairs or even full system replacement. Your blower motor becoming damaged is the fastest way to cause damage to your system as a whole. With no airflow at all expect anything that can overheat to overheat. As well as your evaporator coil freezing up during the summer months which we will get into next.

• Frozen Coils: If your air filter is dirty during the summer and you have central air, the evaporator coil that sits on top of your furnace and is connected to your outdoor central air unit can freeze up, causing serious cooling issues. The refrigerant in your HVAC system is made to absorb heat from the air that passes through when your blower motor is on. Your refrigeration lines condensate when your unit is running. Without airflow the refrigeration lines will get cold enough to freeze. If you thought a dirty air filter blocked airflow imagine a huge block of ice the width of your ductwork. Then the evaporator coil will have to thaw and the water will leak onto your heat exchanger and maybe even some onto the electrical components of your furnace. Not to mention the damage it will cause to your outdoor compressor as it tries to compensate for the frozen coil and becomes over-worked and over-heated.

How Often Should You Change Your Air Filter?

Every household is different, most will need to replace it at least every 1-3 months. If you have pets, allergies, or live in a dusty area, you might need to replace it more often. For a good estimation on how often you should be changing yours try taking our detailed quiz here. Trust me, spending a few bucks on a new filter is way cheaper than repairing a burned-out motor or compressor.

Common Mistakes Homeowners Make

• Using the Wrong Size Filter: Always check your system’s manual or measure your current filter to get the right fit.

• Waiting Too Long to Change It: A filter that’s completely clogged won’t just affect air quality—it could shut down your entire system.

• Picking the Highest MERV Without Checking Compatibility: Higher MERV ratings mean better filtration, but some systems can’t handle the reduced airflow. Like I said before most households don't need to go above a MERV 8, the higher ratings only increase in price and restrict your airflow more causing more strain on your HVAC system.

Final Thoughts

Your air filter isn’t just about clean air—it’s about keeping your HVAC system in top shape. A simple habit of checking and replacing your filter regularly can save you money, prevent breakdowns, and keep your home comfortable year-round. If you don’t want to deal with remembering when to change it, our subscription service that delivers filters to your door can be a great option.

Visit our homepage www.filtersender.com, we look forward to working with you.