Furnace Filters: How to Decide

Furnace Filters: How to Decide

The primary job of the furnace filter in your Santa Cruz home is to protect your furnace from damage, but higher-quality filters can also improve indoor air quality by removing pollen, mold spores, pet dander and other irritants from the conditioned air.

Furnace filters are rated by a MERV value, or minimum efficiency reporting value. The ratings range from 1 to 20, with higher values representing better air filtration, but also greater resistance to airflow. The best choice for a furnace filter balances the needs of the system, airflow requirements and desired air quality. Here are how the basic types of filters compare:

  • Fiberglass Filters:These filters have a low MERV rating of 1 to 4 and are primarily designed to protect your furnace, often with a flat, thin fiberglass medium. They are inexpensive and disposable, but only remove 10 percent of air pollutants.
  • Washable Filters:These filters can be washed and reused, but require frequent maintenance, are higher priced, and only have MERV ratings of 1 to 4.
  • Disposable Pleated:These filters are relatively inexpensive, with MERV ratings of between 6 and 13, thanks to the larger surface area provided by folds in the filter. They must be replaced often, but remove about 45 percent of air pollutants.
  • Disposable Electrostatic: With MERV ratings of about 10, these disposable filters feature a static charge that attracts more pollutants than standard filters, without restricting the airflow as much as heavily-pleated filters.
  • Reusable Electrostatic:With a MERV rating of 8, these are not as efficient at cleaning the air as disposable electrostatic filters, but they can be reused, saving money over their lifespan.
  • High Efficiency Filters:These filters are thicker than standard versions and may not fit all furnaces, but they provide MERV ratings of up to 16 and remove up to 85 percent of pollutants. For some systems, the airflow restriction may be too excessive.

For more information about each furnace filter type, talk to our team at Valley Heating, Cooling, Electrical. Visit our website for in-depth information on most HVAC topics, or just give us a call at (408) 868-5500.


Our goal is to help educate our customers in the South Bay Peninsula and Santa Cruz areas of California about energy and home comfort issues (specific to HVAC systems).