Three best furnace filters
It's important to change your furnace filter regularly for two reasons.
First, the quality of the air you breathe will suffer if the filter is dirty. A blocked filter leaves dust, mites, pollen, and other contaminants floating in the air. That's particularly unpleasant if you suffer from allergies.
Second, a clogged filter means your system has to work harder than it should. It consumes more energy, which results in higher bills.
Fortunately, a new filter is a quick and easy solution, although choosing the right one can be a bit complicated. We've put together the following buying guide to provide the information you need when shopping for a new furnace filter.
Considerations when choosing furnace filters
Size: You'd think that size would be obvious, but it's not as straightforward as that. Dimensions can be "nominal." In other words, it might be called a 16 x 15 x 1 (inches) filter, but height and depth could each be half an inch smaller. Usually that half an inch makes no difference, but it can. Before you order a filter, measure your existing filter and make sure you get an exact replacement.
Thickness: Thicker filters are more efficient than thin ones because they have more surface area, but that doesn't mean you should replace a filter that's one inch thick with a filter that's four inches thick -- it probably won't fit!
MERV: The minimum energy reporting value is the rating you'll usually see, and while there are a couple of others, it's the scale (MERV 1 to MERV 16) that most manufacturers use. MERV 8 to MERV 12 are those most suitable for household use. At the lower end, the filters trap pet dander, pollen, dust mites, and so on. At the higher end, they're filtering smoke, very fine dust, and even bacteria.
Some manufacturers quote a percentage, for example, the filter will trap 90% of airborne particles. This is particularly true of washable filters, which aren't covered by MERV ratings (though comparisons are often quoted). The problem is that particle size is not given. Mold spores, for example, are much larger than cement dust. The numbers might sound impressive, but they're not really telling you anything of value. Whenever possible, always go by the MERV rating.
Furnace filter features
Pleats: Almost all filters are pleated because pleats have more surface area to trap airborne particles. However, the level of filtration -- the size and type of particles -- varies.
Electrostatic charge: This is added to some filters during manufacture. It works like a magnet, attracting particles to the filter surface, and it lasts for the lifetime of the filter. "Electrostatic" shouldn't be confused with "electrical." It doesn't need a power source.
Antimicrobial: An antimicrobial component might be added to the filter fibers, providing additional protection.
Hypoallergenic: Several manufacturers make hypoallergenic filters.
Charcoal: This can sometimes be used to help absorb odors.
HEPA: HIgh-efficiency particulate air filters catch extremely small particles, which sounds ideal if you have allergies. Unfortunately, these filters are too dense for most furnaces or air conditioners.
When to change the furnace filter
Most manufacturers recommend that you change your furnace filter every three months. However, if you have pets, you might need to replace it more often. If you've had any work done in your house, that can also increase the amount of dust and debris trapped in the filter. Experts suggest that you check the filter once a month.
Q. Should I choose the highest MERV rating available?
A. A lot depends on your personal situation. Higher filtration is great if you suffer from allergies or there's a smoker in the house. However, the average household system can struggle to generate enough airflow to use anything above MERV 10 or 11. If it's a serious issue, you should consult a suitably qualified HVAC technician.
Q. Which is better, a disposable or permanent furnace filter?
A. Unfortunately, there's no easy answer. A pack of six disposable filters costs about the same as the equivalent permanent filter. The former would normally last 18 months, so it's going to be at least that long before you see any financial benefit. The permanent filter still needs to be washed regularly, so some people prefer the convenience of a quick-change disposable item. Of course, the permanent filter has less environmental impact. It's very much a matter of personal choice.
Furnace filters we recommend
Best of the best: FilterBuy MERV 8 Pleated Furnace Air Filter
Our take: Thick, long-life furnace filter delivers excellent performance.
What we like: Large surface area increases effective airflow while trapping large proportion of household particulates. Less clogging means fewer filter changes.
What we dislike: Expensive.
Best bang for your buck: Nordic Pure MERV 12 Pleated AC Furnace Filter
Our take: All the features you need at a budget-friendly price.
What we like: High MERV rating pulls large percentage of contaminants from the air. Great for allergy sufferers and pet owners.
What we dislike: Filtration may be too high for some home systems (lower ratings are available).
Our take: Electrostatic benefits in a filter you never need to replace.
What we like: Efficient filtering of most airborne particles. Easy to clean. Lifetime warranty. Economical over time.
What we dislike: Might need to be washed as often as once a month.
Bob Beacham is a writer for BestReviews. BestReviews is a product review company with a singular mission: to help simplify your purchasing decisions and save you time and money. BestReviews never accepts free products from manufacturers and purchases every product it reviews with its own funds.
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