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Decoding Ratings on HVAC Air Filters


Around the South Bay Peninsula and Santa Cruz area, chances are you run your air conditioner enough for your HVAC air filter to potentially make a real difference in your air quality. While not every filter has that ability, understanding filter ratings will help you find one that does.

MERV Helps You Judge Efficiency

The minimum efficiency reporting value (MERV) of an HVAC air filter tells you about its efficiency at capturing airborne contaminant particles. The higher the MERV, the more efficient the filter. Low-efficiency models with MERVs of 1andndash;4 are designed only to keep larger debris particles out of your system. These have almost no effect on your indoor air quality.

Models with MERVs of 5andndash;8 remove enough dust, pollen, mold spores, pet dander, and other contaminants to be sufficient for most households. These are often pleated filters, which last longer than standard fiberglass panel filters. If you have allergies or asthma, a filter of MERV 10andndash;12 is a better choice.

HEPA Filters Provide Exceptional Filtration

A true high-efficiency particulate arrestance, or HEPA, filter can trap 99.97 percent of particles of 0.3 microns or smaller. These achieve MERVs of 17andndash;19. HEPA-like filters are also available, but these are less efficient than true HEPA filters.

HEPA filters provide a level of filtration beyond what most households actually need. In addition, research from the Environmental Protection Agency (EPA) shows MERV 7andndash;13 filters are nearly as effective as HEPA filters.

If you have allergies, asthma or another respiratory condition, however, a HEPA filter might be worth the investment. These filters can't simply be placed in the filter holder because they're so dense they would severely restrict airflow through the system. If you want to use a HEPA filter, consult a technician about installing a HEPA bypass system. This directs only part of the air stream through the filter at any given time, preventing airflow problems.

Visit our website for in-depth information on most HVAC topics, or just give us a call at Valley Heating at (408) 868-5500.

Our goal is to help educate our customers in the South Bay Peninsula and Santa Cruz areas of California about energy and home comfort issues (specific to HVAC systems).

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