Pro tips for changing the air filter in your home

Pro tips for changing the air filter in your home

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Owning your own home comes with a lot of responsibilities including maintenance.

Did you know your air conditioner and heater is the most expensive appliance in your home? It requires maintenance just like your car. One of the fastest, cheapest ways you can give your air conditioner and heater a little TLC is to change your air filter.

Because Brown specializes in servicing air conditioners and heaters, we are often asked questions about air filters. We’re here to help you take the best possible care of the machine that works silently year-round to control the air your family breathes and keeps you family comfortable.

Advice from the pros on changing your air filter

Before you jump in your car to buy an air filter, you’ll need to gather a few pieces of information. You’ll need to determine how many filters you need and what size you need.

How many filters do I need?

Most systems (air conditioner + heater) require one filter. If you are not sure how many systems you have, simply count the number of thermostats you have.

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How do I determine what size air filter I need to buy?

The easiest way to identify the size of your air filter is to take a peek at the filter that is currently in your system. The size of the filter is printed on the outside border of the filter.

Pro tip: Don’t shake the filter. You’ll release all of the particles your filter has successfully captured.

If the filter does not have the dimensions printed on it, you can measure the length, width and depth (thickness) of the filter.

You should have 3 numbers written in inches like this 16 x 20 x 1. Other common filter sizes include 20 x 20 x 1 and 20 x 25 x 1.

Make a note of the filter size…you’ll need to remember it when you’re standing in the store and you’re faced with all of the options.

Pro tip: Add a reminder to your calendar to change your filter every month. In the note section of your reminder, add the filter size and quantity.

Where is the air filter in my HVAC system?

All central heating and cooling systems use an air filter to clean the air you breathe and protect the machine from dirt and dust. This seems like a simple question, but the answer is not so simple. There are endless places your filter could be hiding, so get ready for a scavenger hunt.

The most common places you’ll find your air filter is in the ceiling, wall or floor behind a return air grille.

Pro tip: Usually you’ll find the filter in the hallway close to the thermostat.

For some systems, it is harder to locate the air filter, because it is stored in a slot aka filter rack beside the indoor section of your unit (furnace or air handler). The indoor section is commonly found in the attic, basement or crawlspace.

In rare cases, the filter may be installed inside the furnace. We do not recommend that you replace the filter by yourself under these circumstances. More risk is involved when you remove the panel from the furnace. You may hurt yourself or cause damage to the system. Please call a professional HVAC technician.

How to change your air filter

Replacing your old, dirty filter with a clean, new filter is simple. The only tool and supplies you’ll need is a screwdriver and the filter (one filter for each thermostat).

To replace the filter behind a return air grille in the ceiling, wall or floor,

  • Shut down the system by turning the thermostat to the “off” position.
  • Open the Return Air Grille by sliding the hinge open and allowing the door to open.
  • Carefully pull out the old, dirty filter.
  • Insert the new filter with the arrows pointing away from you.
  • Close the Return Air Grille door and secure the hinges to ensure the door is closed properly.
  • Turn your system back on.
  • Throw away the old filter.

To replace the filter stored in a slot or filter rack by your indoor unit,

  • Shut down the system by turning the thermostat to the “off” position.
  • Open the door of the filter rack.
    Older systems do not have a door. You will see the filter in the open slot.
  • Note which way the arrow on the old filter is pointing. You’ll want to install the new filter in the same direction – toward the furnace.
  • Carefully slide the old, dirty filter out.
  • Insert the new filter with the arrows pointing in the same direction as the old filter. The arrows should be pointed toward the furnace.
  • Close the filter rack.
  • Turn your system back on.
  • Throw away the old filter.

How often should I change my filter

How often you change your filter depends on your home environment, lifestyle and the type of filter you have. If you live in an area that is dust-free, you may only need to change your filter once every 3 months. If you have pets, smoke, or live in a dusty area you will likely need to change your filter much more often.

  • Cheap, see through, fiberglass filters need to be changed every 30 days.
  • Basic, pleated filters need to be changed at least every 90 days.
  • High-end pleated filters last up to 6 months.

The frequency of changing your air filter also depends on whether you have family members with allergies or asthma. People that are sensitive to airborne particles require superior indoor air quality and nicer air filters.

A good rule of thumb is to inspect your filter once a month to see how much dust and dirt has collected. If your filter is dirty and clogged, it’s time for a new filter.

Pro tip: You cannot change your filter too often. Your family will enjoy the fresh air and your system will enjoy the unrestricted air flow.

Why do I need to change the air filter in my house?

Air filters are a vital, often an underappreciated part of the air conditioning system. Air filters serve two primary purposes: protect your HVAC system and clean the air you breathe.

  • Protect your HVAC system: Every central air conditioning and heating system is dependent on proper air flow. Dirty filters restrict air flow which damages your system over time. Imagine trying to breathe with a pillow over your face. That’s how your system feels with a dirty filter…it cannot breathe. A clean filter will help your system operate the way it was designed.


HVAC Trivia: Did you know your heating and cooling system has over 30 mechanical parts? Just like humans, every part is allergic to dust, dirt and pollen.

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  • Clean the air you breathe: It is hard for dirty filters to capture more dust and particles, so where does it go…it floats around your house and your family breathes it in. Your lungs will filter the dust and particles for you.

The air flow in your home is on a closed loop system called your duct work. New, fresh air is not pulled into your house by your HVAC system. The same air circulates through your home. A little fresh air may race in when you open a door, but the outside air is carrying more dirt, dust and pollen.

When your filter is dirty, it is not able to capture the stuff floating around. Which means you and your family are breathing more dirt and dust than you should. Clean filters help stop the stuff from floating around your house.

What happens if I don’t change the air filter in my house

Dirty filters add a strain to heating and cooling systems which may lead to irreversible damage to your system, higher repair costs, higher utility bills and lower home air quality.

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Remember…a dirty filter is like expecting your system to breathe through a pillow.

The #1 reason why air conditioners and heaters fail is due to restricted air flow from a dirty filter. Over time, the dirt and dust that is not stopped by the filter will circulate through the system and accumulate on the blower wheel and coil.  The restriction strains your system and overtime leads to part failure…higher repair costs.

Your system works harder when it has to breathe through a dirty filter. This added strain requires the system to use more energy to perform the job leading to higher utility bills.

If the filter is old and filled with dirt, it does not have room to attract more dirt. When there is no room on the filter, dust, dirt and pollen are constantly circulated through your home which reduces your home’s air quality.

Common mistakes when changing an air filter

We know changing a filter seems like a simple task, but it’s easy to skip a step.

Be sure to avoid these common mistakes so you can enjoy a successful filter change:

Mistake #1: Leave the filter out of the system.

Too often, we hear the horror story of how a homeowner removed the old, dirty filter, but failed to replace the filter. They had every intention of buying another filter on their way home from work, but forgot. Before they knew it, months passed. Their system stopped working when the weather drastically changed, so they called Brown for an emergency repair

Pro tip: Never operate your system for more than 24 hours without an air filter.

Mistake #2: Install the wrong size filter.

We get it. You went to the trouble of buying a filter on your way home and it turns out it is not the right size. You’re thinking, I can make this work.

This is where the Goldilocks principle comes in handy…not too big, not too small, just the right size.

You’ll have to bend a filter to fit in the space, if it is too large. Usually this creates a crease in the filter. The filter will not work properly, since the entire surface of the filter is not available to clean the air. Over time, the crease in the filter will get bigger and bigger, allowing the filter to be sucked into your duct work leading to blocked air flow and damaged equipment.

A filter that is too small can be sucked into the system leading to problems.

A filter that’s just the right size will provide the filter surface your family needs to breathe easier and your system needs to operate properly.

Mistake #3: Ignore the arrows printed on the filter.

It’s vital you take the time to ensure you are installing the filter in the right direction. Make sure the arrows on the filter are pointing toward the indoor unit (furnace or air handler).

Replacing your filter on a regular basis will extend the life of the most valuable appliance in your home. When in doubt, change it. You cannot change your filter too often. Your lungs and wallet will thank you.

Want more information about home air quality?

If you would like to learn more about how to improve your home’s air quality, check out our comprehensive ebook “9 Frequently Asked Questions about Home Air Quality.” You’ll learn everything you need to improve your home’s air quality, control humidity and how plants, pets and candles affect the air you breathe.

We service, repair and install air conditioners and heaters in the Birmingham, Alabama area. We’re available year-round to answer your questions about your filter, air conditioner, furnace or heat pump. Get in touch with us. We want to help you squeeze every penny out of your heating and cooling system investment.


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