Any air filter rated higher than 13 can restrict airflow to the point of causing damage to your HVAC system, resulting in costly repairs. This reduced airflow can also affect the cooling side of the air conditioner, as the cold coil has a specific preferred operating temperature. This temperature is based on a certain amount of hot air flowing through the coil and the coolant circulating through its copper tube. With a higher MERV filter, this crucial part of the air conditioning system can eventually freeze and become an ice ball, restricting airflow completely.
The MERV rating is a standard measure of a filter's ability to remove particulates from the air in your home. A MERV 13 filter, for example, can remove bacteria, tobacco smoke, car fumes, insecticide dust, pet dander and more. McMaster Carr manufactures the Merv-15 airbags that some universities are testing for face masks. While ASHRAE recommends MERV 13 and 14, it's best to select a filter with the highest possible MERV rating for your specific HVAC system.
MERV filters 9 to 12 are the best filters that a residential HVAC system can accommodate without major system modifications. Most modern HVAC systems have no problem working with higher MERV filters, so millions of homeowners rely on them.