Do High MERV Filters Always Reduce Air Flow?

Learn how high-efficiency air filters can affect your HVAC system's performance and how they can reduce airflow in extreme cases.

Do High MERV Filters Always Reduce Air Flow?

Many people don't consider the impact that a filter with a high MERV rating can have on other parts of the HVAC system. Research has shown that, in general, HVAC systems with high MERV filters have a higher pressure drop across the filter. The short answer is that it can, but it's not usually an issue unless in extreme cases. Most modern HVAC systems are designed to work with higher MERV filters, so millions of homeowners rely on them.

The main risk of using high-efficiency air filters is that they are not changed regularly. If you remember to change your filters regularly, you are unlikely to experience any issues with your HVAC system. A higher MERV rating means more resistance, which in turn means less airflow. When researching HVAC systems, airflow is a major factor. This is because it is essential for the performance and longevity of your oven or air handler.

Airflow is also key to having a comfortable home. Using an air filter with a MERV rating that is too high is just as bad as using one that is too low. Air filters with higher MERV ratings may filter more, but the thickness of the filter material can restrict airflow. This restricted airflow can decrease comfort levels, increase energy use, and accelerate wear of HVAC components. In particular, using an air filter with a too high MERV rating can damage the compressor, heat exchanger, and air conditioner coil.

When buying an air filter from a large store or online, take a moment to review the specifications and look up the MERV rating and any information on airflow velocities. A coarser filter may not always provide better filtration results. A high industrial rating such as a MERV rating may not always tell the whole story. While MERV 8 is known to be effective at filtering contaminants such as pollen, dust mites, sawdust, mold spores and lint from the air, higher MERV ratings will further clean the air. Using an air filter with a too high MERV rating can be as bad as using one that is too low. If you do not replace the filter according to your recommendations, it accumulates dirt and dust, making it more restrictive and less effective in filtering.

The same applies to households with smokers or pets, as MERV 11 air filters better eliminate odors. Twenty percent of the budgeted pressure for air filter pressure drop will leave enough pressure to overcome the resistance of the system coil and distribution system and allow the system to supply the required airflow. A dirty or restrictive filter can cause an ECM engine to use more energy to force more air through the system. They also found “a clear trend towards lower airflow with higher MERV filters for systems that use PSC motors. From sizes to types, qualities and more, here's everything you might need to know about air filters. A trained professional can recommend adaptations to compensate for the consequences of air flow and pressure from a high-efficiency filter and to keep the heating and air conditioning system running efficiently over time. MERV 8 air filters are very common because they are a fairly complete option and are usually quite affordable.

When a filter is in use, it traps and collects particles; the more particles are trapped, the more difficult it will be for air to pass through; when this occurs, the pressure drop of the filter increases. With an inclination of 45 degrees, each filter is approximately 1.4 times the area of a filter that spans the same half of the duct horizontally or with an inclination of 0. The amount of HVAC airflow slowed by the filter equals the filter pressure drop. This then improves the air quality in your home by preventing waste from recirculating in the air.