Furnace Maintenance – How Often to Change the Air Filter

air-filterfurnacemaintenancereplacement

Does the period of change of this air filter have an affect on the longevity of the heating and a/c system? What is a good rule of thumb to require replacement?

Best Answer

Dirty filters not only make the HVAC equipment not last as long, but the low air flow makes them less energy efficient. A dirty furnace does not conduct heat into the air as well and the dirt sticks to the fan blades making it not last as long or spin as easily.

There are two main types of air filters:

The 1" thick ones that look like this: alt text

And the 6" thick filters look like this:

alt text
(source: filterscanada.ca)

Generally the 1" filters are good for a month or two. The 6" thick ones are good for 6 months.

There are also 2", 4", and 5" filters available but generally not at the local hardware store. Some folks who have 6" filters use a 2" + 4" filter and replace the 2" one every other month and the 4" once a year. This seems like a hassle to me, but it might save you $50 a year if you have 6" filters.