HEPA Air Filters: How Effficient Are They?

Air filters in your heating and cooling system are rated by the MERV (minimum efficiency reporting value) ranking. MERV is determined by laboratory tests to identify the smallest airborne particulates the filter media will trap. MERV ratings for residential use range from 1 to 16. The higher the MERV, the more efficient the filter is at removing smaller airborne particulates and improving indoor air quality. In most homes, filters with MERV ratings between 6 and 12 are appropriate. If the household contains occupants with allergies or other sensitivities, however, filters up to MERV 16 can be installed, usually with modification to the HVAC system.

HEPA (high efficiency particulate air) are filters ranked MERV 17 to 20. These are medical grade filters often utilized in hospitals and clinics for their superior air filtration. Made of molecularly bonded glass fiber material, a HEPA filter will remove 99.7 percent of airborne particulates down to 0.03 microns. This includes bacterial micro-organisms, as well as mold spores and pollen.

The high filtration efficiency of HEPA filters imposes a significant restriction on system airflow. Unlike commercial facilities such as hospitals, residential HVAC systems don’t produce sufficient airflow to overcome the restriction of a HEPA filter installed in the ducts. Reduced airflow causes your system to struggle to satisfy temperature demands, waste energy, warm or cool your house less effectively, and eventually damage your equipment.

Whole-house HEPA filters available for residential installations install in a bypass loop that connects to your HVAC ducts, rather than directly inside the ductwork. A whole-house HEPA filter incorporates a blower that draws about 60 percent of the duct airflow into the filter and then loops it back into the ductwork. Since all air in your home is conveyed through your ducts many times per day, this ensures continuous HEPA-grade filtration without restricting system airflow.

At CCAC, Inc., we’re Constantly Concerned About Customers. Give us a call and let us explain more about high-efficiency HEPA air filters to ensure the indoor air quality in your Coastal Bend home.

Our goal is to help educate our customers in Corpus Christi, Texas about energy and home comfort issues (specific to HVAC systems).  For more information about air filters and other HVAC topics, download our free Home Comfort Resource guide.

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