What Is a MERV Rating?

Air Filter in San Antonio, TX

When you start shopping for air filters, you will quickly notice that most products mention something called a MERV rating. What does this mean? Keep reading to find out all about what MERV ratings are and how they work.

What Does MERV Stand For?
MERV stands for Minimum Efficiency Reporting Value. This is essentially a type of measurement used to determine how good of a job an air filter will do. The MERV scale was initially developed by the American Society of Heating, Refrigeration, and Air Conditioner Engineers (ASHRAE). Over the years, it has been adopted by most major air filter manufacturers who now specifically aim for certain MERV ratings when they produce products.

The MERV rating can be a very useful way of comparing filters regardless of their type, size, or materials. The MERV scale runs from 1 to 20, and ratings are assigned based on the size of particles that pass through the filter. Lower MERV levels mean the filter catches less small debris, and higher MERV levels mean it filters more particles out of the air.

What Do Different MERV Levels Mean?
It can be a little hard to understand what MERV means when you just look at abstract numbers. Real-world examples can provide a better explanation of what a filter’s MERV rating will mean. Filters with a MERV rating of 1 to 4 can catch bigger things like pollen, pet hair, carpet fibers, basic dust, and dust mites. A MERV rating of 5 to 8 means the filter can catch everything from the lower levels, along with mold spores, hair spray residue, and cement dust.

At a rating of 9 to 12, filters can catch finer particles like lead dust, automobile emissions, or flour. A MERV rating of somewhere between 13 to 16 can catch very small particles like tobacco smoke and bacteria. The highest rated MERV filters, which are in the 17 to 20 range, will get viruses, carbon dust, and other ultra-fine particles that most filters cannot catch.

Which MERV Rating Should You Pick?
In most cases, you want a filter with a higher MERV rating. Higher MERV levels mean you end up with less dust and grime circulating inside your system. This leads to cleaner air and better AC efficiency. At a bare minimum, ASHRAE suggests a MERV of 6 or more. The US Department of Energy suggests homeowners get a MERV of at least 13 if they want to see energy savings.

Is a Higher MERV Always a Good Thing?
In most cases, a higher MERV rating means cleaner air for you. However, this does not necessarily mean you should shove a MERV 16 filter into your AC system. Filters that block more particles also block a little more airflow. That will not harm your system as long as you have an HVAC designed to handle high MERV filters. However, if your air conditioner is older or smaller, the motor might not be able to pull enough air through the filter. This puts more strain on your system and makes your home take longer to cool down.

To avoid this issue, you need to pick the right MERV for your air conditioner. Check your system manual to see what MERV level the manufacturer recommends. Usually, they will give you a range of suggested MERVs. You can definitely get benefits by picking the highest recommended option, but you will probably want to avoid exceeding it.

Is MERV Different From HEPA?
When discussing MERV ratings, it is also helpful to learn a little about HEPA ratings. These two air filter designations get frequently confused. However, they are technically separate things. HEPA stands for High-Efficiency Particulate Air, and it is a type of high-efficiency filter. HEPA filters are frequently used in hospitals, manufacturing facilities, and other industries where the ultimate clean air is needed. A HEPA filter usually has a MERV rating of around 17 or 18. These very efficient filters usually only work in machines specifically rated for HEPA filters.

Interested in learning more about improving indoor air quality? Talk to the experts at Rosenberg Indoor Comfort. Our team of highly qualified San Antonia HVAC technicians can help with all sorts of services. We can help you with repairs, maintenance, and installations, and we work on both commercial and residential buildings. To schedule an appointment or learn more about us, give us a call now.