The filter in your furnace is an essential component that removes pollutants from the air before it gets heated in your furnace and then circulated in your home. Additionally, the filter in your furnace keeps these particles out of your furnace, where they can build up and reduce its efficiency. There are many filter options available on the market; learn how to select the right one for your system.
Understanding the ratings is a key part of choosing an air filter. Most filters are rated on the Minimum Efficiency Reporting Value (MERV) scale. These numbers – from 1-16 for residential use – rate how well the filter removes the smallest particles from your indoor air.
- MERV 1-4: These are the cheap fiberglass filters that probably came with your furnace. They only filter particles over 10 microns in size, doing very little to improve your indoor air quality. However, if kept clean, they do a good job of maintaining system airflow.
- MERV 5-8: These filters are medium quality. You’ll notice that the material inside these filters is pleated. They remove particles down to three microns in size. These offer a good balance between maintaining air quality and proper airflow.
- MERV 9-12: These are high-quality filters that can remove particles down to one micron in size. At this MERV level, you need to make sure they’re not impeding airflow. Your trusted HVAC professional can advise you on this.
- MERV 13-16: These are the highest quality standard filters available, removing particles down to .3 microns in size. They’re more likely to slow airflow, however.
- MERV 17-20: Also known as HEPA (High Efficiency Particulate Air) filters, these filters go above the standard MERV rating because of their ability to remove 99.97 percent of the particles .3 microns and above in your air. Some modifications to your HVAC system may be necessary to use this type of filter in your home.
Now that you know the rating system, make sure to change the filter in your furnace following these instructions:
- When to change: Check your filter each month. It’s pretty obvious when it’s clogged with debris, but when in doubt, change it.
- Size it: Check your furnace’s current filter for the appropriate size for your equipment.
- Follow the arrows: The markings on the filter will indicate which side should be inserted into your furnace. The arrow should point toward the furnace.
Have questions about the filter in your furnace? Call Paschal Heat, Air & Geothermal. We have been serving northwest Arkansas homeowners for more than 40 years.
Our goal is to help educate our customers in Northwest Arkansas about energy and home comfort issues (specific to HVAC systems). For more information about furnace filter and other HVAC topics, download our free Home Comfort Resource guide.
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