Furnace Filter FAQ

The following are answers to commonly asked questions about furnace filters.

Why you need a furnace filter?

Furnace filters at a minimum are designed to protect the furnace from large airborne particles. Without this protection, the dust and dirt will build up and bog down the blower moter causing it to die prematurely. Furnace filters can also be used to improve the indoor air quality by removing smaller airborne particles from the air.

How often should a furnace filter be changed?

How ofter a furnace filter should be changed depends on a number of factors: system operating time, the quality of the filter and location of the home. The more often and longer the furnace runs the more often the filter will need to be changed. As for quality, cheap fiberglass throwaway furnace filters will need to be changed more often (monthly) then the more expensive pleated media filters (3 months.) If you live in a dusty location (construction, desert, etc...) you will need to change your filter more often.

What is a furnace filter efficiency or MERV rating?

Almost all furnace filters are labeled with a MERV (Minimum Efficiency Reporting Value) rating number. The MERV value indicates the filter's ability to trap particles ranging in size from 3.0 to 10.0 microns. This number is derived from a test method designed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) and is intended to help people compare filters. The higher the MERV rating, the more efficient the filter is at removing airborne particles. Typical residential filters will have a MERV rating of 1 to 11.