Low- vs. High-Efficiency Air Filters: Which Should You Choose?
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Low- vs. High-Efficiency Air Filters: Which Should You Choose?


You want the cleanest air possible for your Portland area home, but improving your indoor air quality isn’t as simple as installing the most efficient air filter you can find. The choice of low- vs. high-efficiency air filters depends on your home situation and your heating and cooling system design.

The MERV Scale

The MERV (Minimum Efficiency Reporting Value) scale helps you decide about low- vs. high-efficiency air filters. This system ranks filters based on how efficiently they trap air contaminant particles of certain sizes. The higher the MERV number, the more efficient the filter.

  • MERV 1 to 4 – Basic filtration to protect your heating and cooling system.
  • MERV 5 to 8 – Sufficient filtration for those without allergies or asthma.
  • MERV 9 to 12 – Mid-efficiency filtration that helps reduce allergy and asthma symptoms.
  • MERV 13 to 16 – High-efficiency filtration that traps tiny contaminants, such as smoke particles and bacteria.
  • MERV 17 to 20 – HEPA (High-Efficiency Particulate Air) filters that trap bacteria and viruses efficiently enough to reduce the spread of infection.

Why Higher Efficiency Isn’t Always Better

The more efficient a filter, the greater the density of its media. A dense filter slows down air moving through it, forcing the fan motor to work harder to maintain optimal airflow. Filters above MERV 13 are too dense for many residential systems. These are likely to strain the motor and cause early failure, unless modifications are made to the equipment.

Choosing low- vs. high-efficiency air filters requires finding a balance between efficient filtration and sufficient airflow. The good news is that filters of MERV 7 to 13 are almost as efficient as HEPA filters, according to U.S. Environmental Protection Agency research. If you want a filter with a MERV higher than this, consult a heating and cooling professional first.

A true HEPA filter may benefit you if you have respiratory health concerns. To add whole-house HEPA filtration, however, you may need a bypass system. This add-on system redirects air for filtration without impeding airflow. HEPA filters also come in stand-alone air cleaning systems.

At Roth Heating & Cooling, we can help you navigate the world of air filters and cleaners, and improve the air quality in your Portland area home.

Our goal is to help educate our customers in the Metro Portland area about energy and home comfort issues (specific to HVAC systems).

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