Furnace Filters And Health

Mar 21, 2023

Furnace Filters Affect on Home Health and Efficiency

In the Midwest out HVAC systems are particularly important.
Learn why you should regularly changing your home's filter to keep your equipment running efficiently and your home comfortable.


In Minnesota, we spend 60 percent of our utility bill on heating and cooling our homes. If you use a furnace or central air conditioner to keep your home comfortable, it is important to change the filters regularly, especially the filter found in your furnace. Clogged filters can impact how well your equipment runs, lower its efficiency, and even shorten its lifespan.

Why are filters important?

Furnaces pull cold air from your home via the cold air return ducts, heat the air, and then deliver it to the house via the warm air supply duct that splits off to various rooms. The furnace filter is usually found between the two ducts.
The filter’s primary purpose is to protect the equipment by removing dust, particulates, and debris from the air before it goes into the furnace. Some filters can also improve air quality by removing very fine particles like pollen and pet dander.
A filter that is clogged with dust and particulates restricts the air flow into the furnace, making it work harder. The furnace will then take more time to deliver warm air to the house. Restricted air flow can also lower the efficiency of the furnace. Forcing it to run with a clogged filter for too long will damage your furnace.
Regularly changing the filter keeps your furnace running efficiently and your home comfortable.

How do you replace a furnace filter?

Changing a furnace filter is a fairly simple task. The basic steps are as follows, but make sure to refer to your furnace’s manual for exact directions.

1. Turn off your furnace.
2. Remove the existing filter.
3. Insert the new filter — make sure it is the right size. Also make sure to face it the correct way by looking for the arrows or markings that are often on the cardboard part of the filter frame.
4. Turn your furnace back on!

Filters can be purchased from your local hardware store, Amazon, or even big box stores such as Target and Walmart.

How often do filters need to be changed?  Which filter should I buy?

 The short answer is that it depends. It is best to check what your furnace’s manual recommends. Some filters should be replaced every month, while others only need to be changed every three to six months. Some filters can be rinsed and reused. If you look at your filter and it is grey with dust, change the filter. If your filter is about an inch thick, it likely needs to be replaced every month. A filter that is three to six inches thick can likely last several months.
If your furnace uses an inch-thick filter, be sure to select one with a Minimum Efficiency Reporting Value (MERV) rating of 8 or less. When the MERV is higher than 8 for this type of filter, it can negatively affect the air flow through the furnace.
Filters with high MERV ratings are very restrictive in order to remove extremely fine particulates from the air. While this might initially be helpful, once it is clogged, a high-MERV filter quickly becomes too restrictive for your furnace. To prevent damage, replace your high-MERV filter at least every three months. If you are interested in a filter with a MERV rating higher than 8, plan to use a 4-inch filter instead of a 1-inch thick filter. An HVAC professional can retrofit such a filter to your current ductwork if you don’t already have a slot that can hold a 4-inch filter.



 Outside Resources

How Can I Tell That My Filter Needs To Be Changed?
Blog post detailing when you should change your furnace filter.

Air Filter Buying Guide
Consumer Reports buying guide.


MN Department Of Commerce Home Energy Guide
Guide on general home energy efficiency from the Minnesota Department of Commerce.



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