High MERV ratings are the most effective for air quality, but they can also cause damage to your air conditioning system. A higher MERV rating means greater resistance, which translates to less airflow. This can lead to reduced comfort in both hot and cold climates, as your system may not be able to supply enough heating or cooling to the entire house or just one or two rooms. Additionally, a highly effective air filter can quickly become clogged with contaminants and start to increase the pressure drop. The Minimum Efficiency Value (MERV) rating of an air filter measures how effectively it prevents dust and other contaminants from passing through the filter and into the air stream.
MERV indices range from 1 to 16, with filters with higher MERV indices trapping small particles more effectively than those with lower ratings. Air filters with a MERV rating of 7 to 14 or higher can have pressure drops of 0.05 to 0.3 inches in the toilet, depending on the thickness of the filter and the speed of the air flow. If the furnace is located in a place where the owner can access it to replace the filter and where the location of the furnace allows for an increase in the width of the return duct, then a higher MERV filter may be installed. However, if you choose to use a high MERV filter, you must remember to change it regularly. Otherwise, you may experience problems related to airflow resistance. In addition, if you are using a high MERV filter, you should consider creating multiple filter discs and changing them after each exposure to several people.
This is because high-efficiency particulate air (HEPA) filters trap even smaller particles than those with a MERV 16 rating and are generally used in surgical operating rooms, clean rooms, and other contexts that require absolute cleaning. If you want to use a high MERV filter without increasing pressure drop, you should look for filters with deeper folds that will increase their surface area and allow more air to flow through. Air filters with a MERV level of 13 or higher are recommended for those who prioritize air quality and may have to deal with asthma, serious allergies, and other similar circumstances. Finally, if a homeowner requests a very high MERV filter, they may need to modify or replace the ducts if the pressure drop of the filter is greater than what was assigned in the system design.
