What kind of filter do I need, and how often should I change it?

August 11, 2014

This is a loaded question, but one that we get on a daily basis. The type of filter you need varies based on your situation. Someone who travels for a living and has no kids/pets may not have to change the filter very often simply because the system rarely operates. Where as, a home with a family of six, two dogs, and three cats, may require a higher grade filter that will need changed more often. 

I have a family of three (soon to be four) and two dogs. We have a 4″ MERV 13 pleated filter in our home. However, we are soon upgrading to a new air purification system that will contain a MERV 16 filter. My daughter and I have bad allergies and our dogs shed a lot. We typically change our filter every 4 to 6 months.

Don’t understand MERV? Don’t worry, most people don’t know what it is, and that’s ok. MERV is “Minimum Efficiency Reporting Value” and it is how they rate filters.


What Kind of Filter Should I Get?

Again, this depends on your situation. I suggest that you have one at least MERV 8 or higher. It doesn’t matter if it’s a 1″, 4″, or 6″ filter, just make sure that it’s MERV 8 or higher. If someone in the home has bad allergies I would suggest a MERV 13 to 16. If you’re simply worried about dust, I would suggest a MERV 11 or higher. And, for those of you who don’t care, stick with the MERV 8. It will at least protect your heating and cooling system. Oh, and don’t waste your money on the cheap blue “hog hair” style filters. I know they’re only $.70 at your local hardware, but those “boulder catchers” won’t catch the allergens and debris that will clog up your secondary heat exchanger and your air conditioning coil.

“Someone told me not to install the more efficient filters because they’re too restrictive.”

This is true! They ARE restrictive if you don’t change them often enMERV 16 Filterough. A MERV 16 filter is the most restrictive and will likely need to be changed every 3 to 6 months. Yes, they are more expensive than the average filter, but you get what you pay for. I change our MERV 13 filter every 4 months. We can get 6 months out of it, but we keep the fan “on” on our furnace. Which leads me to another matter, your filter is only doing it’s job when the fan on your furnace is operating. You can’t filter the air when there is no air movement. If you keep your fan on auto, that’s fine, you will get more life out of your filter because you’re not using it!

Most people either go by the packaging on the filters to determine how often to change their filters, while others routinely change their filter monthly, seasonally, or just “when they remember”.

Here’s what I suggest…
Washable filters – Throw it away and get a pleated filter
1″ Filters – Monthly
2″ Filters – Bimonthly
3″, 4″, and 5″ Filters – Every 4 to 6 months

If you have any questions, feel free to call, email, or tweet us @ControlTechHVAC!

Written by Clay Winters, Design Technician @ Control Tech