Photo by Collin Anderson, acquired via

Why Change Your Filter?

Posted October 30th, 2019 under renovations and repairs, money matters.

“If it looks clean, why do I need to change it?” The truth is, your furnace filter should be changed an absolute minimum of four times a year. Even better is to change it every month in winter and summer (the most active heating and cooling periods).

Often a filter might look clean enough, but dust is not always dark or visible. Even a filter that looks clean after several months has, in fact, accumulated dust.

When the filter gets dusty, that restricts the air flow. This is not a sudden event, but rather, a gradual process that you would not notice during your daily life. (However, when changing a dirty filter for a clean one, you likely will notice a difference.)

When the filter is dusty, the motor driving the fan needs to work harder to push the air through. Not only will this reduce the lifespan of the motor, it will also use more electricity.

The reduced air flow will also diminish the heat exchange capacity of your house. The slower the air flow, the less heat it can carry away from the heat exchanger to the rest of the home. This in turn uses more heating fuel, because the house is not being heated as quickly as it could be, resulting in a longer furnace run. (A similar process happens in the cooling season if you have central air conditioning.)

Again, this is a gradual process. It won’t feel like your furnace or A/C have suddenly failed. It will just slowly drain your wallet and reduce your comfort.

So, if the cost of a new filter makes you reluctant to change it quarterly, remember that not changing your filter will shorten the life of your furnace and cost you money anyway.

Meanwhile, running your fan 24/7 all year will actually save you money! An always-on fan maintains an even ambient temperature in your home, which allows you to set the temperature a little lower in winter and higher in summer while still feeling comfortable, reducing how often your system needs to come on.

But, to take advantage, you need to change the filter regularly, not just once a year!

Want to know more about your home heating and cooling systems? Just ask me, I'll be happy to help.


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