Choose The Right Furnace Filter

Changing your furnace filter is not very challenging. Slide the old one out. Put the new one in.

Selecting the right furnace filter is a bit more of a challenge. There are many factors involved. Let’s look at a few.

Your furnace’s specs

furnace filterStart with what your own furnace’s owner’s manual says about the filter you need. If you have the owner’s manual, start there. If not, you may find information on a label on the furnace itself. And, of course, there is the filter currently in the furnace to serve as a guide to a suitable replacement.

What kind of specs are you looking for?

  • You may find minimal air flow rate listed for your furnace. This is an important number to know. If you select a filter that lowers the air flow rate below your furnace’s minimum, you will be forcing your furnace to work harder, which may shorten the life of the blower.
  • You may find that the manual specifies a particular type of reusable filter.
  • You should find the size of the filter
  • You might find a recommended rating for the filter

In this post we are concentrating on disposable replacement filters. If your furnace doesn’t use that type of filter, then what we have to say here is not directly applicable to your situation.

Size

The filter that is currently in your furnace can serve as the guide for what you need to buy. This assumes that the current filter actually fits the furnace correctly and that the furnace is running well with that type of filter.

Most disposable furnace filters have two important bits of information printed on them: their size and the air flow direction. You can also measure the filter to get its size, of course.

Ratings

Ratings are done on at least two different “standard” scales. Knowing what the rating means will help you select the right filter for your situation. Both your air quality and your furnace specs affect your choice.

MERV

Furnace filters are rated on a minimum efficiency reporting value scale. The scale runs from 1 to 16. Residential furnace filters typically fall between 4 and 12. Higher ratings mean the filters remove more particles from the air.

  • MERV 4 filters : filter out large airborne particles, including pollen
  • MERV 7 to 8 filters:  catch mold and pet dander
  • MERV 11 and 12 filters: may be necessary if anyone in your family has severe allergies or a compromised immune system

FPR

If you buy your furnace filters at The Home Depot, you may find filters marked with an FPR rating instead of a MERV rating. The Home Depot developed the FPR rating and it closely resembles the MERV system.

  • FPR 4 to 5 filters are “Good”
    catch large airborne particles including dust, pollen, and pet dander
  • FPR 6 to 7 filters are “Better”
    also catch mold, and bacteria
  • FPR 8 to 9 filters are “Best”
    also catch microscopic allergens, and most smoke
  • FPR 10 and above filters are “Premium”
    also catch odors and smog particles

Seasonal considerations

You may want to use a higher rated filter in high-pollen seasons, particularly if family members suffer from allergies. You may find that you can use lower rated filters in dry climates or in the winter when airborne pollen is not an issue. If you are in a heavy smog area, seasons may not make much difference in your filter needs.

Where to get your furnace filters

You can buy furnace filters at many types of stores both physical and online, including hardware stores, big-box stores, and discount stores.

Interested in more detail on changing your furnace filter? It’s just one of our how-to articles on specific home maintenance tasks.

You may also be interested in our home maintenance schedule. It walks you through a complete home maintenance routine over the course of a year.
Download home maintenance schedule

Changing your furnace filter is not very challenging. Slide the old one out. Put the new one in.

Selecting the right furnace filter is a bit more of a challenge. There are many factors involved. Let’s look at a few.

Your furnace’s specs

furnace filterStart with what your own furnace’s owner’s manual says about the filter you need. If you have the owner’s manual, start there. If not, you may find information on a label on the furnace itself. And, of course, there is the filter currently in the furnace to serve as a guide to a suitable replacement.

What kind of specs are you looking for?

  • You may find minimal air flow rate listed for your furnace. This is an important number to know. If you select a filter that lowers the air flow rate below your furnace’s minimum, you will be forcing your furnace to work harder, which may shorten the life of the blower.
  • You may find that the manual specifies a particular type of reusable filter.
  • You should find the size of the filter
  • You might find a recommended rating for the filter

In this post we are concentrating on disposable replacement filters. If your furnace doesn’t use that type of filter, then what we have to say here is not directly applicable to your situation.

Size

The filter that is currently in your furnace can serve as the guide for what you need to buy. This assumes that the current filter actually fits the furnace correctly and that the furnace is running well with that type of filter.

Most disposable furnace filters have two important bits of information printed on them: their size and the air flow direction. You can also measure the filter to get its size, of course.

Ratings

Ratings are done on at least two different “standard” scales. Knowing what the rating means will help you select the right filter for your situation. Both your air quality and your furnace specs affect your choice.

MERV

Furnace filters are rated on a minimum efficiency reporting value scale. The scale runs from 1 to 16. Residential furnace filters typically fall between 4 and 12. Higher ratings mean the filters remove more particles from the air.

  • MERV 4 filters : filter out large airborne particles, including pollen
  • MERV 7 to 8 filters:  catch mold and pet dander
  • MERV 11 and 12 filters: may be necessary if anyone in your family has severe allergies or a compromised immune system

FPR

If you buy your furnace filters at The Home Depot, you may find filters marked with an FPR rating instead of a MERV rating. The Home Depot developed the FPR rating and it closely resembles the MERV system.

  • FPR 4 to 5 filters are “Good”
    catch large airborne particles including dust, pollen, and pet dander
  • FPR 6 to 7 filters are “Better”
    also catch mold, and bacteria
  • FPR 8 to 9 filters are “Best”
    also catch microscopic allergens, and most smoke
  • FPR 10 and above filters are “Premium”
    also catch odors and smog particles

Seasonal considerations

You may want to use a higher rated filter in high-pollen seasons, particularly if family members suffer from allergies. You may find that you can use lower rated filters in dry climates or in the winter when airborne pollen is not an issue. If you are in a heavy smog area, seasons may not make much difference in your filter needs.

Where to get your furnace filters

You can buy furnace filters at many types of stores both physical and online, including hardware stores, big-box stores, and discount stores.

Interested in more detail on changing your furnace filter? It’s just one of our how-to articles on specific home maintenance tasks.

You may also be interested in our home maintenance schedule. It walks you through a complete home maintenance routine over the course of a year.
Download home maintenance schedule