How Often To Change Furnace Filters?

If you have a furnace in your house, then the question of how often to change furnace filters shouldn’t be new to you. Taking good care of your home is crucial for any homeowner. After all, nobody wants to live in a place that is falling apart at the seams, sometimes literally. From making sure that bills are paid on time to ensuring that all the appliances are working as they should, there are going to be a lot of different things that you will want to pay attention to. For instance, changing out the filters in your furnace is something that you will want to do every few months.

While each and every home is different, you should generally aim to check your furnace filter every one to three months. When you check the filter, if you spot a thin layer of dirt, you should change it right then and there. If you wait for the filter to clog up on its own, you will be doing quite a bit of damage to yourself and your wallet. There will be an increased risk of an expensive furnace repair if you do not replace the filter regularly. In addition to this, because of the thick layer of dirt on the filter, your furnace will have to work even harder to keep the house at comfortable temperature. This means that your energy bills are going to be noticeably higher. These are just a few of the many, many reasons why you need to consider changing out your furnace filter.

With all that being said, there are some owners who want to get the specifics of the situation right down to the nitty, gritty details. A general idea of when a furnace filter needs to be replaced isn’t always good enough. Thankfully, there are some ways that you can come up with a much more precise method of replacing your filter, meaning that you will be able to stay on top of taking care of your house.

Understanding What MERV and Thickness Mean for Replacing Filters

The first thing that you will need to do when you are considering replacing your filter is knowing what MERV is. Most manufacturers will include the MERV alongside the dimensions of the filter on one of the long sides of the filter. Unless otherwise noted, the dimensions of the filter will be written as Length x Width x Depth. This means that you will want to pay attention to the last number as this will be the thickness of the filter. The thickness of the filter will be important for determining how often you should be checking and replacing your filter.

The MERV of the filter should be right beside the dimensions, although it can sometimes be on the opposite side of the filter. MERV stands for “Minimum Efficiency Reporting Value” and is a standard that basically rates the overall effectiveness of an air filter. The higher the MERV, the finer the filtration. The finer the filtration is, the more dust will gather on the filter and it will need to be replaced more often. MERV values can be denoted in one of two ways. For example, if your filter had a MERV value of 6, it would either be displayed as MERV 6 or M6, depending on the manufacturer. Now that you understand where to find these values and what they mean, you can now begin learning about how they correlate with replacing filters.

How Often Should Furnace Filters Be Changed?

Knowing How MERV and the Thickness of the Filter Affect Replacement

MERV, thickness of the filter, and the rate that you check and replace the filter all go hand in hand. The thicker the filter is, the less often you will have to check and replace it. The MERV value will also play a role in this as filters with a higher MERV value will need to be replaced more often. There is a simple and efficient way to remember this, though:

  • MERV 1-4 and under two inches thick will need to be checked every three months.
  • MERV 5-8 and under two inches thick will need to be checked every one to two months.
  • MERV 8+ and under two inches thick will need to be checked every month.

It goes without saying that the filters should be replaced if they are dirty. There’s no point in putting a dirty filter back in as it will create a whole slew of problems and the potential for many more. You should also keep in mind that filters with a MERV value above 8 are generally not recommended if they are under two inches thick. These filters will clog extremely quickly, becoming a money sink for your entire house. In addition to this, they can also cause a pressure drop in the furnace system, which is never a good thing. If you are adamant about looking at a filter with a MERV value above eight, then you will want to look for ones that are well above two inches and are pleated.

Factors That Influence How Often To Change Furnace Filter

There are a few things you will want to take note of when you are planning out when exactly you are replacing your furnace filter. Some factors will increase the rate that you should replace the filter. These factors can include the following:

  • Having pets
  • Having frequent guests over
  • Having the thermostat fan on ON instead of AUTO
  • Having doors and windows open frequently
  • Having someone who smokes in your home
  • Having a bunch of dust everywhere

These factors will increase the number of contaminants in the air that the filter will have to filter out. Pets produce hair, among other things. Guests can carry any contaminant that can be found outside. Having the thermostat on ON will keep air moving throughout the house constantly, which means that more dust and dirt will be picked up. A similar principle applies to having open windows and doors except that the latter can also include pollen, which is a common allergen. Smoking is one of the biggest reasons why filters wear out more quickly, as is dust. If your home has any of these factors, you should reduce the time between checks for the filter.

This time reduction can be up to you but the more factors that apply to you, the more frequently you will want to check the filter. For instance, if your air filter has a MERV value of 4 and is under two inches thick but you have a few pets in the house, you would reduce the time that you check the filter from the usual three months to around two months. This prevents the filter becoming completely clogged and causing more problems.

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