How Do I Choose A Replacement Furnace Filter?

30 April 2019
 Categories: , Blog

When it comes to furnace maintenance, there are few things more important than swapping out your furnace filter regularly. It might be the fact that it's so simple to do that makes people underestimate the importance of doing it. While there's no one-size-fits-all schedule for when it should be done because of the differing sizes of houses and furnaces, not to mention the variety of furnace filters available, you should check it every three months or so, as a general rule. It should happen more if you have pets or live near construction zones. So what happens if you don't change it? Your heat exchanger can overheat, your furnace will run inefficiently, and your air will be unhealthy. A clogged filter is a common cause of furnace failure. But how do you choose a filter?


The most obvious first step is that you need to figure out what size filter you're going to need. Of course, the easiest way to do this is simply to pull out the old filter and note the size. But perhaps you've just moved into a new house and the furnace is missing a filter. In that case, you can simply search online for the make and model of your furnace. If there are complications to that approach, call a company that specializes in furnace maintenance services for your model of furnace and ask. The most common sizes are 10x20, 14x25, and 24x25.

Efficiency Rating

When choosing a filter, you need to consider the level of filtration you want. The easiest way to do that is to take a look at the efficiency rating or MERV score. MERV stands for minimum efficiency reporting value. It's an efficiency scale created by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE). The MERV scale is 1-20 with 20 being the highest possible efficiency reporting value. A filter with a rating between 17-20 would likely be used in a building that requires ultra-efficiency, like a cleanroom where carcinogenic, radioactive, or pharmaceutical materials are handled. Most residential filters, on the other hand, are between 1-12 on the MERV scale.


The material of filters also generally corresponds to their MERV rating. Filters with a rating of between 1-4 are lower quality and typically made of flat-panel fiberglass or washable aluminum mesh. A filter with a rating of between 5-8 would likely be a pleated cotton-polymer blend. A filter with a rating between 9-12 would be on the higher scale of residential filter efficiency. It would likely be made of micro-fine fiberglass or synthetic cotton.

For more information about replacing your furnace filter, contact a company like Polar Aire Heating & Cooling Inc.