FAQs About Air Filter Ratings

No matter what type of heating and cooling system your St. Louis, MO, area home has, it’s important to check its air filter once a month. The air filter captures particles from your home’s air, which keeps your home cleaner, reduces excess wear and tear on the heating and cooling equipment, extends the heating and cooling system’s lifespan and helps you breathe easier. Choosing an air filter can be tough, which is why our technicians at Hoff Heating & AC offer these 10 FAQs and answers for homeowners in and around St. Louis.

1. What Rating System Is Used for Heating and Cooling Air Filters?

The rating system used for heating and air conditioning air filters is called the minimum efficiency reported value, or MERV, system. This rating system was designed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. This is a group of professionals who each have decades of hands-on experience with building, designing, installing, maintaining and repairing heating, ventilation, refrigeration and air conditioning systems.

2. What Is the Range of Ratings for Air Filters?

MERV ratings range from 1 to 20. The higher the MERV rating, the more particles 0.3 microns in size the filter is able to capture. It’s important to keep in mind that higher MERV ratings aren’t necessarily better for your heating and cooling system. At the top end of MERV ratings, large particles will quickly clog the filter’s tiny pores, and the airflow rate through the filter will decrease. This causes the heating or cooling system to work harder, which will increase your utility bills and negatively impact your comfort.

3. What Type of Air Filter Material Has the Highest Rating?

Spun fiberglass is the material with the highest potential MERV ratings. There are fiberglass air filters available in all MERV ratings. MERV ratings are highest for pleated filters with a thick filter media. The fiberglass is situated across folds of cardboard, creating a pleated type of effect. Flat fiberglass filters and filters with thin media have lower MERV ratings.

4. Does Washing a Reusable Air Filter Affect Its MERV Rating?

Electrostatic filters are reusable. Instead of using fiberglass or paper, they use an aluminum frame. The aluminum has an electrical charge, and charged particles are attracted to it. Washing is necessary for an electrostatic filter. Vacuuming the filter then washing it in clean, soapy water removes all of the particles the filter captured. When the filter is covered in dust and dirt, its ability to capture more particles drops. Washing the reusable filter allows it to reach its full MERV rating potential.

5. How Do I Find Out What MERV Rating My Heating and Cooling System Needs?

New heat pumps, furnaces and air conditioners may require a minimum MERV rating in order for you to maintain the manufacturer’s warranty. Your owner’s manual will explain this in the air filters section. Air filters come in many sizes. Each size of filter is available in a range of MERV ratings. If you choose a lower MERV-rated filter than what the manufacturer recommends, you could end up voiding the warranty and having to pay out-of-pocket if parts fail. Our Hoff Heating & AC technicians can also tell you what MERV rating you should pick for the air filter in your St. Louis area home.

6. Does Damage Affect an Air Filter’s Rating?

No, damage to the filter won’t affect its MERV rating, but it can affect the filter’s performance. If you buy a filter and notice that it’s dented, wet, moldy or perforated, return or exchange it for a new one. Those types of damage impact the filter’s ability to capture particles. Moldy or wet filter material could make your home’s indoor air quality worse. Be sure to buy the right size of air filter. Don’t try to jam a thicker or bigger air filter into the heating and cooling system’s housing. Jamming in the wrong size of filter could decrease the heating and cooling system’s efficiency and your home’s indoor air quality.

7. Which Particles Does a MERV 8 Filter Catch?

An air filter with a MERV rating of 8 captures 75% to 85% of particles 3 to 10 microns in size. Particles in this size range include hairspray droplets, furniture polish, mold spores and cooking dust or aerosols. They capture less than 20% of particles smaller than 3 microns in size. An air filter with a MERV rating of 8 is inexpensive. It will typically be flat and made of a medium layer of media. This filter is acceptable if you are in good health, don’t have furry pets and have no allergies, asthma or other breathing disorders.

8. What Particles Can a MERV 12 Air Filter Collect?

An air filter with a MERV rating of 12 is a good quality of filter. It will capture 90% or more of particles 3 to 10 microns in size. It will also capture 80% or more of particles 1 to 3 microns in size. Particles in the 1 to 3-micron size range include lead dust, flour, auto fumes and combustion fumes. A filter with a MERV rating of 12 captures less than 20% of particles smaller than 1 micron in size.

9. When Should I Choose a MERV 16 or Higher Air Filter?

If you have severe asthma or allergies, a breathing disorder, compromised immune system, an elderly household member or baby in your home, consider an air filter with a MERV rating of 16 or higher. This type of filter captures bacteria, smoke and respiratory droplets. It removes 90% or more of particles 3 microns or larger in size. It also removes more than 95% of particles 0.3 microns or larger in size. This is considered a superior grade of air filter, and it’s what hospitals use in their surgical suites and intensive care units. Clean environments, including computing facilities and laboratories, also use this type of air filter. MERV ratings of 17 and higher are considered high-efficiency particulate air filters, and they capture 99.97% or more of microns 0.3 microns in size.

10. Which Air Filter Rating Is Best for People With Asthma?

If you have asthma, choose an air filter with a MERV rating of 14 or higher. Filters at this MERV rating level capture more than 75% of bacteria 1.0 microns or larger in size. They also capture the sneeze droplets from a person’s nose and respiratory droplets from coughing. This lowers your risk of respiratory illnesses that could trigger your asthma. Air filters with MERV ratings of 14 and higher capture smoke, mold spores and pollen, which are common asthma triggers. This MERV level removes 75% to 85% of viruses from your home’s air, which may also help you avoid an asthma flare-up.

Hoff Heating & AC is a top-notch provider of air filters in St. Louis and the surrounding communities. Homeowners count on us for heating and air conditioning maintenance, repair, replacement and installation services. We’re proud to offer geothermal, new construction and semi-annual maintenance plans. To learn more about air filter ratings or to schedule service with our NATE-certified technicians in St. Louis, contact us at Hoff Heating & AC today.