Should I always use the highest-rated filter available?

It depends on a couple factors. First, is your system new or old? One might think the higher the MERV rating the better. But sometimes using the most efficient filter (higher MERV rating) is not the right answer. This is because as filter efficiency increases, there is a corresponding increase in the level of air flow resistance. A highly-efficient filter may restrict air flow to a level that will damage your HVAC system by placing additional strain on the fan motor.

Second, does someone in your home suffer from allergies or asthma? Do you have small children or an elderly person living in your home. Each of these groups are more susceptible to the adverse health effects associated with poor indoor air quality, therefore, you may want to ensure you install the best in indoor air filtration.

Regardless, you should use a filter rating that best corresponds to the requirement of your HVAC system (and health concerns), and yet provides maximum air cleaning benefit. When in doubt contact your manufacturer, your installer or an HVAC maintenance company.