All about air filters:

I’m often asked by customers how often an air filter should be changed. Like most things, the answer is circumstantial. The average frequency OR generic answer to this question is every 3 months. However, I have found it will depend on these factors mentioned below.

  1. Do you have pets and/or kids? You will most likely find that the filter will need to be changed more often if you fall into these categories.
  1. How clean is your house? If you are very tidy, you will find yourself changing the filter less often.
  1. Do you have respiratory problems such as Asthma or Allergies? If so, you would want to change the filter more often to reduce contaminates in your home.
  1. Is construction going on in the home? If so, ideally you would want to shut the system down during construction hours and cover all your registers. However, if that ship has sailed you will want to check the filter immediately. 
  1. Is there a smoker in the house? You will most likely find that the filter will need to be changed more often if you fall into this category.

Just to be clear, the white filter below is clean and the dark one is dirty. If you find your air filter dirty (see the pictures below and notice the gray clumps)… you waited too long. Increase the frequency until you find your filter between dirty and clean. Tip: Dust tends to be gray in color, it’s mostly dead skin and dust mites. Don’t Google dust mites, you don’t want to know…Also, some filters these days have charcoal in them and will appear dark in color when clean. So if it sais “charcoal” act accordingly.                           

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In the age of smart phones and programable thermostats, the “past due dirty air filter” problem is very easy to avoid. I recommend the smartphone option. Most people interact with it daily, and will find many offers to solve forgetfulness. Such as….

  1. Mark it in on your calendar. Be sure to set the frequency accordingly so that you get reoccurring reminders.
  1. Set a reminder using the reminder app. Siri, Google Assistant, Alexa, Bixbe (maybe)….

If the smart phone isn’t your thing, I recommend going to the daily planner or wall hung calendar. Again, if you interact with your calendar more than you thermostat, you will want to rely on it as your primary reminder.

Regardless of your use of a smartphone or paper calendar, you will want to set a reminder on your thermostat as a fail safe. If your thermostat doesn’t do that, it may be time to replace it based on age. This feature has been on most thermostats for the past 20+ years.


Changing your air filter is important for the following reasons.

  1. Indoor air quality. With the increased use of insulation to receive energy savings, the ability for unclean air to exit the house has suffered.                                                                The movement of air through the home (specifically between the conditioned space and the attic) often times will travel through a fiberglass OR cellulose insulation barrier. Like an air filter, this layer of insulation catches a lot of dust, and serves as a home to rodents and everything they bring to the table. Sort of like a built in filth filter…. However, this unintended filter never gets changed until you remove it from the house! I suspect it to be the primary culprit of increased respiratory issues i.e.”sick building syndrome”. The problem can be solved by removing porous insulation and replacing it with polyurethane spray foam. Spray foam has proven itself a superior insulator, it doesn’t pass air, and won’t serve as a home for rodents.  
  1. Is the 2nd floor of the home noticeably hotter in the summer? A dirty air filter will exacerbate this problem. In fact a thicker air filter can also cause this issue because they both will restrict air flow. Chances are your duct work is undersized to begin with which is the primary cause of this problem to begin with. Be sure to consult a professional in regards to whether or not your ductwork can handle that “upgraded” filter before pulling the trigger on that purchase. I have found the only air cleaner to enhance air quality while not significantly cutting air flow to be the Trane CleanEffects. For more info on that system click here. 
  1. Equipment life. A furnace cools itself with the air passing through the filter. So if the air is restricted, your furnace will be overheating constantly. This eventually leads to a breached/cracked heat exchanger i.e. new furnace time. If you think you’re safe because you have a heat pump or Ac only system, think again. Instead of damaging the heat exchanger you will damage the compressor, and these systems are more expensive to replace than a furnace.

4.      Operating Efficiency. Better airflow/clean filters saves energy.



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