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How Often to Change Your HVAC System’s Air Filter

This is a reminder that we cannot bring up often enough: you must change (or clean) the air filter in your HVAC system routinely during the year as part of regular maintenance. This filter protects the cabinet that houses your air conditioner and furnace—or heat pump, in some cases—and prevents dust and other debris entering via the return air vents from creating damage. But if the filter is left alone, it will become congested, resulting in a choke in the airflow and a system that’s inefficient and in danger of suffering crippling malfunctions.

“Okay, but how often do I have to do this?” you ask. It depends on the type of filter you use. Let’s look at some examples.

Permanent filters

In general, we don’t recommend permanent filters for an HVAC system, since they aren’t as effective at actual filtration as temporary filters and they can develop mold and mildew over time. If you do have a permanent filter, you’ll need to have it removed and cleaned using a garden hose on low pressure every two months on average—perhaps a bit more frequently during times when you use the AC or heater more often.

Panel filters

These are the least expensive type of temporary filters. You can usually pick them up in packs from hardware stores where each filter costs around a dollar. They have less powerful filtration levels than most pleated filters, but still work for many HVAC systems. But they need frequent changing, usually once a month. (Make sure to write in marker along the side of each filter the date it was put in so you know how long has passed since it was changed.)

Pleated filters

These more expensive filters are usually made of polyester, rather than the fiberglass of panel filters, and are more powerful at filtration. (Be cautious about going too powerful with a MERV rating above 10, because it will restrict airflow.) You will need to change these filters every 3 to 6 months. Check on them routinely to see their progression.

Comfort Flow Heating has provided quality service and installations in Eugene, OR since 1961.

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