What Is The Difference Between MERV 11 And MERV 12

This post may contain affiliate links, which means we may receive a commission if you click a link and purchase something that we have recommended.

It is easy to be at a loss when choosing between MERV 11 and MERV 12. Furnace filters with any of these MERV ratings are effective in trapping large and small solid airborne contaminants.

However, there are subtle differences between them in terms of performance. Here is a simple guide to help you make an informed choice between MERV 11 and MERV 12 air filters.

Is there a Big Difference Between MERV 11 and MERV 12?

There is no significant difference between MERV 11 and MERV 12. Both furnace filters can trap large and microparticles very well. However, the actual percentages of the contaminants that such furnace filters can trap vary greatly.

A furnace filter with a MERV rating of 11 will eliminate at least 85% of large particles that measure between 3 and 10 microns wide. Such large solid particles include dust and smoke.

Furthermore, MERV 11 is enough to remove particles that measure between 1 and 3 microns in diameter. Such particles may be in the form of dander, smoke, and dust.

A furnace filter with a MERV rating of 12 effectively removes large and small contaminants. Such a furnace filter can remove more than 90% of large contaminants 3 to 10 microns wide. It can also remove up to 89.9% of contaminants that are 1 to 3 microns wide.

The difference between MERV 11 and 12 may also be apparent depending on the additional features of the filters. If one filter is pleated while the other is not, the pleated one will be more effective.

This is because pleating a furnace filter increases its overall surface area. The higher the surface area of a furnace, the greater its air filtration capacity.

The level should inform the choice between MERV 11 and 12 of Indoor Air Quality that you target for your home. For example, if you target a slightly higher Indoor Air Quality, it would be wise to go for MERV 12. Nevertheless, installing a MERV 11 furnace filter will be sufficient to keep the air clean and safe for everyone.

Does MERV 12 Restrict Airflow?

Installing a furnace filter of MERV 12 may restrict the airflow in your HVAC system. This is because of the general rule that higher MERV ratings interfere with the airflow.

In addition, such furnace filters force the blower of your HVAC system to overwork to push the air at the required rate. When this process occurs, your HVAC system ends up overworking as it attempts to maintain the ideal temperature in the house.

When your HVAC system overworks, it consumes a lot more power than when it is usually working. Furthermore, any of the components of the HVAC system may get damaged when the blower is overworking. Therefore, repairing your HVAC system or replacing it may be pretty expensive.

Therefore, it is important to choose a furnace filter with a MERV rating that does not interfere with the airflow. Sadly, many people do not give much thought to the relationship between the MERV rating and airflow.

Several factors can determine the extent to which a MERV rating of 12 may restrict your airflow. Here are brief descriptions of some of the most important ones and how they can affect airflow restriction in your HVAC system.

The type of the blower

There are two types of blowers for HVAC systems: Permanent Split Capacitor and Electrically Commuted Motor. Permanent Split Capacitor blower types are more prone to causing high-pressure drops.

The higher the pressure drop, the lower the airflow. Therefore, if you have a MERV 12 furnace filter installed in an HVAC system with a Permanent Split Capacitor, you will experience low airflow.

Electrically Commuted Motor types produce fewer pressure drops than Permanent Split Capacitor ones. Therefore, installing a MERV 12 furnace filter with an Electrically Commuted Motor type will produce minimal interference in airflow.

The size of the filter

Filter size is an essential determinant of the extent to which a furnace filter can restrict the flow of air. The most important indicator of the extent to which a furnace filter can restrict airflow based on its size is the surface area. The higher the surface area, the less the pressure drops—consequently, the lower the impact of the furnace filter on airflow.

Therefore, if you install two MERV 12 furnace filters with different surface areas, the one with a high surface area will restrict airflow less than that with a lower surface area.

Is MERV 11 Good Enough?

MERV 11 is good enough for maintaining a high Indoor Air Quality level. Indoor Air Quality is the measure of the cleanliness of the air in your house.

The higher the number of contaminants in the air in your home, the lower the quality. Conversely, the lower the number of contaminants in the air in your home, the higher the quality.

A furnace filter with a MERV rating of 11 is powerful enough to attract and trap over 90% of microparticles. Microparticles measure between 0.3 and 1.0 microns in diameter. Also, such a furnace filter is powerful enough to collect large contaminants that measure between 1 and 3 microns in diameter.

Such large contaminants, including dust, smoke, and even pollen, can cause many problems to people who are sensitive to them.

For example, when people who have asthma are in such a house, they may begin to sneeze or experience difficulties breathing. This reaction occurs because the contaminants in the air find their way into the upper respiratory systems of the individuals.

Installing a MERV 11 furnace filter can solve the problem. However, if the filter has additional features, including a pleated and electrostatically charged surface, it can attract and trap high percentages of contaminants.

This means that you will enjoy a safe, healthy, and comfortable indoor environment at home or any other premise where you install the furnace filter.

Is MERV 12 Good for Fighting Off Odors?

MERV 12 is suitable for fighting off odors. The MERV rating is high enough to ensure that your furnace filter traps the small and large particles that cause odors. Foul odors in the house arise from the presence of such contaminants.

The contaminants may be from the kitchen, bathroom, or even outside. Notably, the presence of smoke in your house may be a big concern because when the smoke particles settle on surfaces, they start to give off a pungent smell.

Having a MERV 12 furnace filter with a pleated and electrostatically charged surface may be enough to trap such contaminants. The pleated surface increases the surface area that is available for the trapping of small and large contaminants. This ensures that the filter effectively traps very high percentages of airborne particles that may be the cause of a pungent smell in your home.

Also, the electrostatic charge on the surface of some furnace filters is helpful because it attracts contaminants. The contaminants are attracted to the charge because they have an opposite charge on their surfaces.


There is not much difference between MERV 11 and MERV 12. Both are enough to ensure that the air in your home is free of large and small contaminants.

However, the actual percentages of large and small contaminants that furnace filters with these MERV ratings can trap vary slightly. Nevertheless, this is not a big deal. Getting a furnace filter with either MERV 11 or MERV 12 will get the job of filtering the air in your home done.