How Often To Change 1 Inch Furnace Filter? (Easy Clues)

Do you want to know how often to change a 1-inch furnace filter?

One inch HVAC filters is the most common filter size, and they should be changed periodically to keep your home air quality at a high level (here is my review on the best washable filters).

In this guide, I will go over...

  • How often to change 1-inch filters
  • Signs that your filter needs changing
  • Environmental factors that dirty furnace filters
  • How to make sure your filter is installed correctly

Let's get started with this guide!

how often to change 1 inch filter

How Often Should I Change My One Inch Furnace Filter?

Almost all 1-inch furnace filters will need to be changed from 30 to 90 days. Changing the furnace filter at the correct time will help prevent poor indoor air quality, allergic symptoms, and can even help prevent premature HVAC system failure.

Fiberglass Filter

The lower quality fiberglass furnace filters will need to be changed every 30 days, though I never recommend these types of cheap filters.

fiberglass furnace filter

Cotton & Pleated Filter

It's a better idea to go with the cotton & pleated filters and just change them regularly.

Pleated stands for the accordion folds in the filter. These folds increase the surface area of the filter and catches more debris. The higher quality pleated filters will need to be changed at minimum every 90 days but sometimes as often as 30 days.

You should read the manufacturer changing guidelines written on the filter packaging, and choosing a filter with at least a MERV 13 rating is recommended.

Read Also: What Are The Best Washable Furnace Filters?

cotton pleated furnace filter

What Is Your Personal Recommendation?

That being said, as a home inspector, I frequently see dirty filters, dirty furnaces, and dirty air ducts. So during my home inspections, I always recommend just changing 1-inch filters every 30 days.

I recommend every 30-days in order to give my client some leeway in how dirty the filter will get.

However, probably the best way to change the filter is to gauge your personal allergic symptoms with how dirty the filter gets through a visual inspection.

Read Also: What Are The Best Furnace Filters For Dust Control?

How To Do A Visual Filter Inspection?

Another good habit is to visually inspect the filter before and after changing so you can get a visual memory for how dirty or clean the filter actually is.

If you carefully look at a new pleated filter (not fiberglass), it will have a pure snow white look to it. With most houses, after a month, this 100% white color will already take on an off color, usually a very light brown.

Anytime there is a color change in the filter such as light brown --- it's a good idea to change the filter.

If you are doing a visual inspection of the filter, make sure to look at the backside of the filter and not the front. The backside (where the air first hits) of the filter always gets the dirtiest.

Read Also: How To Clean Furnace Filters?

how often to change 1 inch furnace filter (1)

What Are Things That Accelerate Filter Debris?

There are numerous things that can make a furnace filter dirtier than normal.

If you have a house with a shedding pet, numerous occupants, or even carpet over hardwood --- it can accelerate the changing of an HVAC filter.

Your local environment matters also. Do you live in a dusty and arid area? Do you have a dirt or gravel driveway? These environmental particles and pollutants will get into your home and clog the filter --- especially if you leave windows & doors open.

Another common and overlooked hazard is high humidity. If you leave windows open, or if the home's occupants don't use the bathroom exhaust fan during & after showers --- it can dramatically increase the home's indoor humidity.

This indoor humidity will increase the likelihood of mold growth and spores which will necessitate more frequent filter changes.

Read Also: What Are The Best Furnace Filters For Odors?

how often to change 1 inch furnace filter

What Is The Best Way To Change The Filter?

The most important part of changing an HVAC filter is to make sure that the arrow is going in the correct direction.

All furnace filters have an arrow printed along the frame that indicates the way air should be flowing. Furnace filters are always installed on the return side of the air handler, so the arrow should be pointing towards the rest of the rest of the furnace (or towards the evaporator coil).

If you have a furnace filter(s) installed in the ceiling, then the arrow should be pointing up because that's where the air is flowing.

It's also a good idea to take a pen or marker and write the date on the paper frame of the filter so you can verify the age of the filter. In addition to writing the age on the filter, I personally like to set a 30-day reminder on my phone calendar.

I am always surprised on inspections when I see a furnace filter that is a year old and extremely dirty --- it is repulsive.

Read Also: How Often To Change A One Inch Furnace Filter?

Should I Seal The Furnace Filter?

Another thing I find during inspections is that the filter isn't sealed well.

There should be a metal slot that the filter should slide into, and then there should be some type of door or latch that closes in order to keep it sealed. You don't want air flowing around the filter.

Just do a quick check and make sure that the filter is properly sealed so there isn't air leakage. They even sell magnetic strips that you can put over the filter opening in order to seal it.

Where Is The Furnace Filter Located?

​The easy answer to this question is that the filter is located at the furnace or indoor air handler.

Sometimes you will have to remove the cover in order to get to the filter but this is pretty rare.

If the filter isn't at the indoor air handler, then the filter will be located at a large wall or ceiling vent --- sometimes 2-3. These large vents in the wall/ceiling are called return vents, and they are much larger than the small supply vents which are tiny rectangles.

Read Also: What Are The Best Furnace Filters For Allergies?

Final Thoughts On Changing Your 1-Inch Filter

I think you should always know what the manufacturer recommendation is for changing a 1-inch furnace filter, which is almost always in the 30-90 day range.

However, the manufacturer guideline is just that, a guideline, and numerous factors may require you to change it sooner such as pets, indoor dust, moisture, and outdoor pollutants.

On my home inspections, I always recommend 30-days just because this prevents damage to the HVAC system, improves air quality --- albeit at a slightly higher cost. But for a decent quality pleated filter, they are so cheap, less than $15, so changing it every month really isn't a big deal.

However, if you do a visual inspection of the filter at least every 30 days --- while taking into account of any allergic symptoms --- this can also be a prudent way to change your filter.

Read Also: Where Is My Furnace Filter Located?

Other Home Guides

Looking to learn more about home maintenance? Check out our other informative home product reviews and guides!

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Arie Van Tuijl

Arie Van Tuijl

Arie is the founder of Home Inspector Secrets, an online resource dedicated to helping people understand how homes work. He is a licensed home inspector in two U.S states and owns a residential and commercial inspection company. To ask Arie a question, please use the comment box at the bottom of the relevant article.

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