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

Control Tech WebmasterHeating and Cooling5 Comments

Zionsville Indianapolis Furnace Filter

This is a loaded question, but one that we get on a daily basis. The type of furnace air 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 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.

Zionsville Indianapolis Furnace Filter

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.”

Zionsville Indianapolis 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.

This is a typical high efficient filter.

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

5 Comments on “What kind of furnace air filter do I need, and how often should I change it?”

  1. Dave

    Good article Clay, thanks. I never heard about MERV values until I read this and I was wary of the restrictive filters due to what I heard vs. what I now know. Now I understand what I need much better than before.

  2. Yvon

    That is unfortunate to have allergies, I have been lucky enough to not suffer them, although my wife does during the spring. We’ve noticed that she normally doesn’t have any problems in the house, so it would appear that our filter is working, though it is probably time to get it changed. Now if only we had a filter for the outdoors so she didn’t have to stay shut in the house all the time.

  3. Pete

    I use a 20 x 30 x 1: MERV 13 filter on my unit (5Ton A/C) and my computer is set for 250 hours of use which during the 100 deg. Summer months is every month. 2 people, 2 cats in a 2,000 sf home. When I change it, it seems to be fairly clean. In 10 years I’ve never had to clean the ducts or grilles. I wonder if I should go to bi-monthly in the Summer….

    1. Control Tech Webmaster

      Hi Pete! If it’s a 1″ filter; we recommend changing it monthly. If it’s a 4″ or 5″ filter; most of our customers change them every 6 months. Summer and Winter. However, most of our customers with severe allergies tend to change their filter more often. Sometimes 4 times per year with the 4″ or 5″ filters rather than 2 times per year. It is user preference to be honest! That is merely our suggestion!

  4. paul

    Thank God.

    Finally a navigation friendly website that speaks English.
    Your simple MERV chart explanation and the -around the house, life-
    anecdotes to filter performance and replacement need were MORE than appreciated.
    I have a Lennox Healthy Climate PCO3-16-16. The filter that it came with from the install, the part number gets all kinds of results when looking to replace. Many suggestions of similar looking, print wrong way/ dimensions off by 1/4,1/8. All with the same Lennox Healthy Climate name, all the same price.
    (Yes, I am aware the people in china who make the filters might change the layout of the ink on the side of the cardboard housing.)

    If you go to various websites, the lack of continuity in order of description info and image inconsistency from angles and direction of airflow/print on the side of the filters makes for finding a replacement frustrating.
    Amazon is worse with one listing having four images and another with only one image that will not blow up to read the print.

    Now all I have to do is find a flow rate chart of all the filters. I do not want to put in an after-factory filter with less MERV for winter, more for summer and still put too much air load on the blower.

    Anyways, thanks for being human and trying to help us.

    Paul

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