The MERV Mystery: Choosing the Right AC Air Filter for Clean Air

Most maintenance tasks for mechanical systems (including vehicles) are best done by trained professionals, with specialty equipment and training. However, there is a vital air conditioning/heating system task that should be done by homeowners, and it takes no special equipment and a minimum of training. Matter of fact, consider this the training needed for this simple task.

Finding the AC Air Filter

System configurations may vary by brand and size, but finding the filter should be relatively easy.

• Find the central air handler cabinet, usually in a closet, garage, or utility space.
• Air is moving through the air handler through large ducts. One duct will bring air in from the house, and one will move air back to the house. The AC air filter will be found in the duct receiving air from the house. This is most often at the base of the air handler.
• The filter will simply slide in and out of a slot, so it is easily replaced.

Types of AC Air Filters

There are two major types of AC filters.

• Most air filters consist of paper or synthetic fibers. The gaps between the fibers determine the size of airborne particles the filter can capture. These filters cannot be reused.
• A few systems employ a synthetic fabric filter that can be cleaned with water. After a thorough cleaning, the filter can be reinserted and reused.

Efficiency Ratings for AC Air Filters

Look for a numeric rating on the AC air filter packaging to determine which filter is right for your system. There are two rating systems: the Minimum Efficiency Reporting System (MERV) or the Micro-particle Performance Rating. Both rating systems denote the percentage of airborne particles of a given size that will be captured by the filter. MERV ratings range between 1 and 20: MPR ratings range between 300 and 2200.

• MERV 1-4 filters capture pollen, dust, and fabric fibers (carpet and clothing) particles
• MERV 5-8 filters capture mold spores, pet dander, and cement dust particles
• MERV 9-12 filters capture legionella, exhaust fumes particles
• MERV 13-16 filters capture most bacteria, and particles the size of sneeze droplets
• MERV 17-20 filters capture most viruses and particles from tobacco smoke.

The MERV 13 equivalent in an MPR rating is about 1900.

Does that mean that you should find the highest rated air filter for your residential system? No. That would be too easy. Filters rated above MERV 13 or MPR 1900 have fiber openings too small to let sufficient airflow for residential systems. This puts too much pressure on the blower motor which pushes air through the filter. (Check your owner’s manual for complete details.) Filters with a rating above MERV 13 are considered HEPA filters, used for hospital and laboratory systems.

How Often Should My AC Air Filter Be Changed?

Since air filters are very efficient at capturing airborne particles, it does not take long for the entire surface of the filter to get covered. If this covering builds up, it will restrict airflow through the air handler, the portion of the system responsible for heating, cooling, and dehumidification.

The result is:

• Poor performance—it struggles to make the home comfortable
• Poor efficiency—it uses more energy to do the same tasks
• Frequent repairs—the clogged filter makes components work harder, resulting in early failure
• Shortened lifespan—a constantly clogged filter will reduce the number of useful years from your system

Air filters should be changed at least once every three months. A prudent approach would be to:

• Determine the proper rating for your home’s heating and cooling system
• Purchase 4 filters
• Schedule a phone prompt to remind you to replace the filter regularly

Stop Guessing Which AC Air Filter is Right For Your System, Call The Professionals

Changing your AC air filter is vital, but it’s only one part of total system health. Ensure your air handler, blower motor, and other components are running efficiently by scheduling a complete AC maintenance appointment with Northwind Air Conditioning and Heating today.

A professional tune-up prevents costly breakdowns, improves air quality, and keeps your system performing at its best all year. Don’t wait for trouble—call us to book your service and protect your investment! Contact us and get the help you need.