How will a High Efficiency Filter Impact My HVAC System

 In Indoor Air Quality

Air filters play an important role in the overall performance of your HVAC system by improving overall indoor air quality and also allowing air to properly circulate throughout the home. Each HVAC system has a specific air filter size and shape, but there are many different types of air filters available, which naturally raises the question of which filter you should use in your home?

One popular way to compare air filters is to look at their MERV ratings. People commonly assume that a higher MERV rating equates to a “better” air filter. However, that is not always the case.

What are MERV ratings?

MERV, or Minimum Efficiency Reporting Value, is a scale for measuring how effective air filters are at removing tiny particles from the air. Filters are tested in laboratory conditions, and the lowest (“minimum”) score from those tests is used to determine the MERV rating. MERV is a 20-point scale; higher numbers indicate that a higher percentage of smaller particles is filtered from the air. However, residential air filters almost never rate above 16 on the MERV scale, and in many cases you may not actually want a filter with a very high MERV rating.

Why a higher MERV isn’t always better

There are several reasons why MERV ratings are not necessarily the best gauge to use when choosing air filters:

  • Restricted airflow – To filter out tinier particles, a high-MERV filter must be woven more tightly and have smaller openings for the air to pass through. Less airflow means that your HVAC equipment will have a harder time keeping your home comfortable, and will use more energy and could reduce the lifespan of an HVAC system in some cases. Using pleated filters can help, but air filters with very high MERV ratings would likely require a different ductwork design or stronger fan motor to compensate for airflow issues.
  • Lifetime performance – MERV measures the minimum efficiency, not the average efficiency. Sometimes, filters with middle-of-the-road MERV ratings can have a better lifetime performance than those with higher MERV ratings.

Using a Air Filters for Coronavirus

Several recent articles have promoted the capacity for high MERV filters to filter for coronavirus. While it’s true that, in a laboratory setting, some filter manufacturers have successfully trapped particles and viruses using a MERV rated filter of 14 or higher, by itself, using an upgraded HVAC filter is not enough to protect people from COVID-19. If you are interested in improving indoor air quality beyond a filter rated for your heating and cooling system, we recommend supplementing with an in-line air purifier like the iWave-R or REME HALO.

If you are concerned about indoor air quality in your home, consult with one of our team members to get a better vision of what’s possible and makes the most sense for you and your family.


When you choose Pharo Heating & Cooling for your home, we bring specialized expertise in home comfort. From heating and cooling to air purifiers and air filtration, one call connects you to a team that can handle a full range of system repairs and replacements. Start by requesting an estimate anywhere in the Madison area.

Contact us today to discover healthier home comfort options.

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