How To Choose An Air Filter

Air filters are an essential part of your air conditioning system. 

It serves two purposes: keep the air in your home clean AND keep your air handler or furnace clean.  The latter is vital to prolonging the service life of your system. So it’s in the best interest of both your health and wallet to change those filters regularly.

So how often should you change your filters?  

The answer is it depends on several factors: 

  • Do you have a busy house with kids and pets?
  • Do you have carpet or hardwood floors?
  • What type of filters do you have?  

A general rule of thumb is every 1-2 months for 1”-2” thick filters and every 4-6 months for 4” thick filters.  

What is the best filter to buy?  

The most important thing is to buy the correct size!  A filter that doesn’t fit properly will let the air bypass it, thereby defeating the purpose of filtering.  You need to know the length, width, and thickness.  This information is written on the cardboard frame of the existing filter, and if not, it will be a trial and error process.  You can always call a service company to help you with this part, but they will most likely need to come to your house.

Once you determine the size, then you can move onto efficiency.  

Filters are rated by something called MERV – Minimum Efficiency Reporting Values.  This number allows you to compare different filters’ performance; basically, the higher the number, the better it is at trapping particles.  For 1” and 2” thick filters, you should look for a minimum of MERV 8.  If you are lucky enough to have a 4” filter, you should be able to find at least a MERV 11 (the thicker filter allows for a higher MERV rating because of the extra face area).

PRO TIP: If your filter is located at the air handler or furnace, make sure the system is off before trying to change it.  It will be much easier to get the old one out and the new one in.