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Which Furnace Filter Should I Use?

Filters are everywhere. Your car has an air filter, an oil filter, and used to have a fuel filter known as a carburetor. Of course, they all do the same thing: remove contaminants from a fluid. Whether that fluid is air, water, oil, or gasoline, a filter removes dangerous or irritating particles from the flow. By capturing particles at the start, before air is heated, cooled, or forced through your ventilation system, it is much easier to keep indoor air clean.

As an added note, there is no difference between a furnace filter and air conditioner filter. If you have a combination HVAC and furnace system, they often use the same filter since they pull air through the same vents and registers. This is why it’s so important to change out your filter every three to six months.

Filters, Filters, Filters

Air FilterA lot of effort and research has gone into building better and simpler filters and filtration systems. That research has gifted us with a wealth of options for your home furnace filter. Simple materials have removed the need for a standardized frame, since filters can be made in almost any size. All you need to do is look at the currently installed filter to see what size replacement is needed. Once you know, it’s time to match needs and preferences.

The most important number on any filter, aside from the dollar cost to you, is the Minimum Efficiency Reporting Value (MERV). This number ranges from 1-20 and is a relative rating for how efficient the filter is. Higher numbers are better.


Fiberglass – These disposable filters are the cheapest and most common filters you’ll find. Popular for rented dwellings and residences, disposable fiberglass filters cost as little as $1 and simply prevent large-size particles (dust, lint, etc) from getting swept into the ventilation system. Fiberglass filters are very simple and have a MERV score of 1-4.

pleated polyesterPolyester – Rather than being flat, as in the case of disposable fiberglass filters, many polyester filters are pleated (similar to the air filter in your car). Fairly inexpensive (home filters are roughly $4-5), they’re better at filtering out particles. The pleats offer a larger surface area than a regular flat panel, giving them a rating of 5-13. Pleated filters offer less resistance, reducing the strain on your blower fan for quieter operation.

Electrostatic – Usually sold in a disposable form, electrostatic filters use a self-charging cotton and have a decently high MERV rating (averaging a 10 on the MERV scale).

Washable – Washable or reusable filters vary by material, but can be found in polyester, electrostatic, and HEPA types. Costs and MERV ratings apply, though the washable variants typically have a lower MERV score than the cheaper disposables.

High Efficiency Particulate Arrestance (HEPA) – These are considered the very best in filtration. With a MERV score of 17-20 and an annual replacement requirement, they are long lasting and highly effective as a filtration device. Unfortunately, HEPA filters require a large space for installation. They are not common to residences and need to be specially designed for during the installation of the ventilation system.


For more advice on air quality and filtration systems, call your home comfort experts at (217) 866-1596 for your Free Whole Home Inspection and Analysis. We are available 24 hours a day, 7 days a week to answer any questions you might have.

We also offer an ongoing Home Maintenance Plan to help ensure you not only have regular heater/furnace maintenance and tune-up checks, but also saves your money!

Cassel Home Comfort Heating & Cooling, situated in the Champaign IL, is committed to being your best HVAC contractor choice in Central Illinois in both Value and Customer Service!

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