Air filters play a more important role in your HVAC system’s overall efficiency than most people expect. An old air filter, or one which does not suit your system, can result in increased energy usage and parts wear and can reduce air quality and unit effectiveness. Smaller filters need replacement every few months and larger ones can last up to a year, but factors such as pets, carpeting and pollinating plants can greatly affect the life expectancy of any filter. 

When the time comes to replace your filter, you’ll need to know a few key things:

  • The dimensions required by your system
  • What MERV ratings it can accept.
  • What MERV rating is best for your usage.

The first is easy to determine. Air filters are sold with their dimensions rounded to the nearest inch, so you can measure your current air filter and find one that will fit easily. Note that there is no consistent order to the measurements, so two filters of the same size might be sold as 10” x 25” x 1 or 25” x 10” x 1. A properly sized filter should fit without being forced—if it bends or tears, you’ll lose efficiency and let particles into your system and home. Gasket tape can be used to create a tighter fit for smaller filters.

Once you have the size figured out, MERV (Minimum Efficiency Reporting Values) ratings come into play. Filters are rated from 1-16 based on what percentage of particles they remove from the air, with 1 being the least effective and 16 the most. Not every system can utilize high-rating air filters, however, as they create more air resistance and thus put more pressure on your HVAC system’s fan. Higher rated filters also need more frequent replacement. Most home systems function best with a filter rated between 8-11, with normal residential systems peaking at 13.

 If you’d like to know more about air filter selection and installation, or have any other heating, air conditioning, or ventilation problems, you can contact Around the Clock Heating & Air Conditioning for expert advice and service in the Los Angeles area.

Our goal is to help educate our customers in Los Angeles, North Hollywood and surrounding areas 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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