How to Choose the Right Furnace Filter

by James Florence


Furnace filters come in a variety of styles, so it’s critical to choose one that’s compatible with your particular system. Photo: Moore Mechanical Heating & Air Conditioning ©2014

Most homeowners understand the importance of regularly changing their furnace filters, but when it comes to choosing a product, few realize the extent of their options. Far from a one-size-fits-all affair, furnace filters range from disposable fiberglass units to high-efficiency pleated models, so it’s important to consider several factors before making a decision.

When choosing a furnace filter, the first thing you should do is familiarize yourself with the MERV (minimum efficiency reporting value) rating system, which is how filter efficiency is evaluated. The MERV rating of a filter denotes three things: the ability of the filter to capture dust, pollen, pet dander and other particles; the filter’s airflow resistance; and the filter’s expected operating life. At the baseline are 1-inch disposable fiberglass filters: with a MERV rating of 2-3, they provide minimal filtration while having little effect on indoor air quality. On the opposite end of the spectrum are high-efficiency models like HEPA filters, which can filter up to 99.7 percent of particles, including dust mites, pollen, viruses and pet dander.

While the filtration strength of a high-efficiency filter makes it an attractive option, there are many potential issues to be aware of. Because of their thickness, high-efficiency filters can restrict airflow in some furnaces, requiring them to work harder and potentially overheat. They’re also considerably more expensive than lower-rated products, and their ability to capture particles means they need to be replaced with greater frequency.

For the average household, a filter with a MERV rating of 6-10 is a good option, as it will provide a balance between functionality and affordability. A MERV 6-rated disposable pleated filter, for example, is relatively inexpensive but still able to capture most spores, mites and other particulates. Even better is a MERV 10-rated electrostatic filter, which contains self-charging electrostatic fibers that actually attract airborne particles.

Because of the potential for compatibility issues between a filter and your furnace, it’s a good idea to consult an HVAC professional for guidance in choosing the right product.

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