Safeguard your family's health and protect your furnace by choosing the right furnace filter. You'll breathe easier, and so will your furnace.
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Choosing a Furnace Filter
A furnace filter is all that stands between the furnace burner and the dusty surroundings, and it also protects people from breathing contaminated air recirculated by the blower.
It’s important to choose your filter wisely, because a furnace with the wrong filter won’t work efficiently. A filter that removes the smallest particulate matter provides the cleanest air, but it might not provide enough airflow for the furnace.
On the other hand, furnace performance can be adjusted when clean air is the number one priority. That’s why a consultation with an HVAC technician is a must before shopping for a more efficient filter than the one you have now.
What Is a Furnace Filter?
A furnace filter is a rectangular piece of fibrous filtering material, typically mounted in a frame. There’s usually one mounted in a channel behind the air intake cover on the furnace itself, and there may be others installed in return vents. The most common sizes are 16-in. x 20-in., 20-in. x 25-in. and 16-in. x 25-in., but there are other sizes available as well.
Types of Furnace Filters
Filters can be disposable or washable, pleated or non-pleated. Some are electrostatically charged to better attract pollutants. The fibers may be natural, such as cotton or cellulose; a light metal like aluminum; or a synthetic material like polyester or fiberglass.
Over the years, filter efficiency has improved to provide cleaner indoor air. The Minimum Efficiency Reporting Value (MERV) rating, ranging from 1 to 20, identifies a filter’s ability to remove particulate matter. The higher the MERV, the better the filter.
Typical MERV ratings for residential furnace filters are between 6 and 12. If you’re concerned about indoor air quality, the Environmental Working Group recommends a MERV 10 or higher.
Furnace Filter Features
When shopping for a furnace filter, check MERV rating first. Other important factors include:
- Disposable/Washable: Homeowners tend to prefer throwaway filters, which means keeping extras on hand. A washable filter, on the other hand, can last for years, but washing can be time-consuming.
- Pleated/Non-Pleated: Non-pleated filters with fiberglass or polyester fibers are inexpensive and provide good airflow for the furnace. But to keep the air in your house clean, you’ll need the extra filtration area of a pleated filter.
- Thickness: Most filters are one inch thick, but some can be two to five inches. Thicker filters provide better filtration, but they don’t fit every system.
- Electrostatic: Most small particles in the air carry an electric charge. Electrostatic filter media attract and remove these more easily than uncharged media.
- MPR: This is the Microparticle Performance Rating established by 3M. It ranges from 600 to 2,800 — the higher the number, the better the filtration. Most residential filters range from 1,200 to 1,900.
Best Filter for a Healthy Furnace
It isn’t always all about air quality. Protecting the furnace is a filter’s primary task, and a non-pleated filter that provides plenty of airflow may be all you need. The Aqua-Flow frameless filter comes in pre-cut sizes or in a roll, and you can cut it to fit. It’s MERV 6, better than many non-pleated filters.
Best Anti-Allergen Filter
To control airborne pathogens, including bacteria and mold spores, you need a high-efficiency filter. The disposable Filtrete 1900 Premium Allergen, Bacteria and Virus Air Filter features a pleated design as well as electrostatically charged fibers. Its MERV rating of 13 betters that of most other residential filters. It can catch aerosol from sneezes as well as smoke, pollen and other debris.
Best Odor-Removing Filter
Got a problem with smelly pets, smokers in the house or persistent odors from the kitchen? The Filtrete MPR 1200 Allergen Defense Odor Reduction Filter includes an active carbon layer to neutralize odors.
This disposable MERV 11 filter removes microparticles and allergens. It’s mid-range in price, so you can keep several on hand without breaking the bank.
Best Washable Filter
Washable filters cost about three times as much as disposable ones. But considering they can last for years, while disposable ones need changing every two to three months, they’re a good investment.
The MERV 8 Trophy Air Washable Filter, made from easy-to-clean aluminum, is electrostatically charged to remove dust particles, pollen, mold spores and even smoke. Buy two so when one needs cleaning, you can replace it and take your time with washing and drying.
Best HEPA Filter
People who are particularly sensitive to allergens and need the extra protection of a high efficiency particulate air (HEPA) filter should consider the Aerostar Pleated Air Filter.
Its MERV 13 rating puts it squarely in HEPA territory. It’s capable of filtering out particles as small as 0.3 microns, but the furnace filter needs to be changed every 90 days to work as advertised. Fortunately, it’s not that expensive.
Best Filter for High Humidity
When the air is humid, particles cling more easily to filter media. That makes it more likely for high efficiency filters to clog and reduce furnace performance.
The FilterBuy MERV 8 Pleated Furnace Filter offers enough stopping power for pollen, allergens and mold spores while providing plenty of air circulation for the furnace. The synthetic fiber filter media prevents mold colonies from growing, a concern in humid environments.
Best Filter if You Have Pets
Pets bring joy to the household, but they also bring pet hair, dander and odors. The Aerostar MERV 11 Pleated Air Filter can filter out particles as small as one micron. Because it does this with an electrostatic charge, it also provides plenty of airflow for the furnace.
On the mid to low end of the price scale, this filter needs replacing every 60 to 90 days — more frequently during periods of peak usage.
Best Smart Filter
Yes, bluetooth-enabled furnace filters are a thing. The Filtrete Smart 1500 MPR, MERV 12 filter boasts an electrostatic media that catches particles as small as 0.3 microns, effectively removing dust, mold spores, pollen and smog. It lasts from six to 12 months, longer than many filters.
If you install the app on your iPhone or Android device, it will warn you when it needs changing. If you sign up with Dash Replenishment, it will even automatically order its replacement.
Best Filter for Dust Control
Home inspector Arie Van Tuijl recommends a minimum MERV rating of 11 for dust control, but filters tend to clog at that efficiency in a dusty environment.
The MERV 11 Filtrete 1,000D Micro Allergen Dust Plus Filter can hold twice the number of dust particles as most comparable filters, or the equivalent of 50 dust wipes. The filter media is electrostatically charged for efficient dust removal while minimally impacting airflow.
Best Furnace Filter Value
Homeowners without air quality issues who are most concerned with protecting the furnacedon’t need a high-efficiency filter. The Filtrete MPR 300 Clean Living Basic Dust Filter works for them. The MPR corresponds to MERV 5, on the low end. But this electrostatic filter is one of the least expensive on the market, and it outperforms comparable non-electrostatic filters.
