Air Filter Maintenance Guide

Keep Your Air Filter Working Like New with Advice from Our Experts

Forced-air heating is the most popular method in the United States for keeping a home warm. An essential component of forced-air heating is the air filter. Originally, the purpose of air filters was to keep large dust particles from damaging the equipment. Today, however, air filters have tighter weaves designed to trap much smaller contaminants. The result is cleaner indoor air and healthier occupants.

Change the Filter Regularly

For optimal system health, remember to change your filter regularly. If you have central air conditioning, keep in mind that the same blower motor and ductwork circulates air in the summer, meaning you need to remember to change the air filter all year round. Usually, that means checking the filter monthly and changing it every three months or when the seasons change.

Failure to replace the air filter can present some negative results, including:

  • Lower AC / heater system efficiency
  • Higher energy bills
  • Increased carbon footprint
  • Diminished home comfort
  • More repairs to keep the strained equipment running
  • Poor indoor air quality
  • An air filter with air passing through it

Filter Efficiency

The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) established a standardized method for testing air filter efficiency back in 1987 called Minimum Efficiency Reporting Value (MERV). All air conditioning and heater filters today are given a rating on the MERV scale, which ranges from 1 to 16. Technically, filters can also rate 17-20, but these are High Efficiency Particulate Air (HEPA) filters and are not designed for use in residential heater and air conditioning systems.

Filters are rated on their ability to trap smaller and smaller particles. Different types of filters have different MERV ratings:

  • Electrostatic filters: MERV 1-4
  • Throwaway filters: MERV 1-8
  • Cartridge filters: MERV 5-8
  • Pleated filters: MERV 5-8
  • Box filters: MERV 9-16
  • Bag filters: MERV 9-16

A Few Words of Warning

Before you go out and buy the best MERV 16 bag or box filter you can find, consider that upgrading to the highest efficiency air filter possible presents its own problems:

  • Poor fit – Most furnaces have slots that accommodate one-inch thick air filters. High-efficiency filters are thicker, making them impossible to use unless you have the slot modified. Also, without a proper fit, contaminants can make their way around the filter and circulate back into the air you breathe, decreasing the filter’s effectiveness.
  • Diminished airflow – Filters with extra tight weaves reduce airflow, which increases your utility bills and can even cause premature equipment failure.
  • Increased cost with little air quality difference – High-efficiency filters cost significantly more than low or medium efficiency options. They may be able to trap minuscule particles, but unless you have respiratory problems, you probably won’t notice a difference between MERV 7 and MERV 14 filtration.

Your best bet is to pick a mid-range filter no higher than MERV 8, which can trap particles as small as 3 microns—such as hair spray, pudding mix, dusting aids, and mold spores. Remember though, if your furnace came with a MERV 1 to 4 filter, the equipment may require some modifications to perform well with a higher efficiency filter. Only a licensed contractor should perform such modifications. Your local Aire Serv® technician is glad to assist you with this.

Download our Air Filter Replacement Checklist

Contact Aire Serv—Trees Clean Air. So Do We.

In the end, a comfortable, efficient, clean home is based on a combination of choosing the right air filter and changing it regularly. For help selecting the right filter, or for inquiries about modifying your existing system, please contact us at Aire Serv today. Our 200 heating and cooling franchise locations let us serve customers across North America.

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