Furnace Filters, How Long Will Mine Last?
It all depends! Furnace filters come in a wide variety of performance characteristics including filtration efficiency (known as MERV rating) and static pressure performance. A filter with high static pressure measurements will cause more stress on your furnace blower motor and other furnace components. It also means that it is likely your furnace is using more electricity to operate as a result. Another factor that impacts the longevity of each filter is the environment your furnace operates in.
The Environment Makes a Difference
Home environments differ, sometimes dramatically. Do you have two people living in the home? Four? Six? How about Pets? Multiple pets? Hobbies such as woodworking? Do you burn a lot of candles? Is your basement battling excessive humidity (60% or above) most of the year? You get the picture. All homes are not the same and that means many times that effective filter lifespans will vary from home to home.
Filters are not all the same! As mentioned above MERV ratings indicate how well a filter will do at removing particles of specific sizes out of the airstream. Always check the specific ratings of your filter. Some may only perform highly on particles of 5 microns or higher. Others may perform substantially better at filtering "fine" particles which are defined as particles that are 2.5 microns or less according to the EPA, but may also cause high static pressure as a side effect. If your filter is contributing to a high static pressure within the system you may want to have it replaced if it is due to loading or a new filter type installed if it is clean and still resulting in high static pressure. Certain filter designs can help you achieve both high level air filtration and very low static pressure!
According to the EPA a single human hair averages between 50-70 microns in size. The EPA also states particles less than 10 microns can enter your lungs and blood stream. The smallest particles often may have the largest impact on your health so this may be something you want to consider when making a filter or air cleaner investment.
As mentioned above, not all air filtration is the same. There are many factors that will influence how long your filter lasts. Additionally, what are the most important aspects of a filter to you? Is it to keep your furnace and coil clean to maximize airflow and reliability? To minimize the impact of negative environmental elements on your health (i.e. dust & smoke)? Or both? Your heating and cooling service provider should be able to provide you with an array of choices and help you choose what filtration system will achieve your goals.