When Should I Change My Furnace's Air Filter?

February 26, 2015

Sometimes we’re asked what is the most important thing that Knoxville area homeowner's can do to protect their air conditioning and heating system between their scheduled PLUS Maintenance Tune-ups? Our advice is simple; remember to change the heating and air conditioning air filter. Buying new furnace and return air filters is extremely important to the effectiveness of your HVAC system, not to mention your home's air quality. Did you know indoor air pollution is among the top five environmental health risks? It’s not thought of often, but it is extremely important to consider. Changing the air filters is not difficult for most Knoxville homeowners, but there are usually two challenges to actually accomplishing this task:

  1. Knowing just how often to replace your furnace or air conditioner filter.
  2. Remembering to change air filters when needed.

When To Change Your Air Filters

Most filters have a timeline printed on the box or plastic. It may read "Lasts up to 3 months" or "Change filter every 90 days". Check out the filters at the store and you'll see that some are meant to only last a month, while other manufacturers (like Honeywell) have created media air cleaners with filters meant to be exchanged once every 6-12 months. The standard seems to be once every few months for most higher quality filters, but we have a rule of thumb that we recommend our friends and family to go by. If they're dirty, change them! A dirty air filter can exacerbate or cause damage to expensive parts, like your compressor, so it's better to change it out more often than neglect it. If you want to listen to the manufacturer's recommended limit, we suggest marking the date on the filter when you swap it out, and programming a reminder for yourself in your phone or on a calendar. Also note that your filter manufacturer sometimes has a different recommendation from your HVAC system manufacturer.

Determining how often to change your air filters relies upon several factors:

  • Which air filter your system requires
  • The overall air quality of your Knoxville area home
  • Pets – Birds, cats, dogs, hamsters (do you have one?), etc.
  • Occupancy of the home
  • General air pollution in the Knoxville area or construction taking place nearby

For your standard 1"-3" air filters, the manufacturers basically tell you to change them every 1 or 2 months, which is in fact a great rule of thumb. Still, generalities may not be suitable for your specific needs. If you have to endure light to moderate allergies, you might need to upgrade your air filter or change them even more regularly than OEM specifications. On the other hand, if you're in a less populated area, own a less occupied home (like a vacation home) or an area with few automobiles and trucks, changing your air filter every 12-months may be quite sufficient. Why do we call out our beloved pets? They have a tendency to shed, which can clog your air filter in no time, just like a vacuum. Naturally, the air filter is just doing its job by containing pet hair and dander, but exceptionally dirty filters can cause weak HVAC performance.

In summary:

  • Vacation home or single occupant homes without pets or allergies: Change 6-12 months
  • Common suburban home without pets: Change every 90 days
  • Add a dog or cat: Change every 60 days
  • More than one pet or have allergies: Change every 30-45 days

How To Remember To Change Air Filters

Here’s an easy way to stay on top of this; sign up for the Service Experts Email Club. This is a convenient way to get money-saving discounts and other helpful information on your smartphone, tablet or desktop. But wait… there’s more, your email subscription preferences let’s you set a reminder to change your Knoxville area home's air filter every 30, 60, 90, 120 or 365 days, or a specific date of your choice.

How to replace your return air filter

Most people know how to replace the air filter in their equipment, but some houses have an additional filter in the return ducts. Whether you have one or not is dependent on which HVAC system you have. Your unit is engineered to handle a certain amount of pressure in your home, and the more filters you have the more the blower motor works, which can reduce the lifespan of your system if it isn't designed for it. Discovering whether you have a return filter and replacing it is easy:

  1. Find your return air vents.
  2. Some covers have screws and some have tabs. Unscrew or pull tabs to remove from the wall.
  3. Inspect for a filter. If one is in place, pull it out and record the size.
  4. Verify the filter type is the one recommended by the manufacturer.
  5. If filter is dirty, replace with the manufacturer's recommended filter of the same size and type.
Crazy as it may seem, filters can really alter your home's airflow, which is why we recommend asking the manufacturer. A top tier HEPA filter that is designed to catch smaller dust will restrict airflow more than a cheaper filter. With restricted airflow comes greater pressure on your system, so you need to verify that your HVAC system was built to handle it. Otherwise, you might experience uneven heating and cooling efficiency in your home, and system parts may die off much faster than otherwise.

 

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