If we were looking to buy a new filter today for our HVAC (heating, ventilation, and air conditioning) system, we’d aim for a medium-efficiency filter with a MERV rating in the 8 to 13 range, which can clean the air throughout your home almost as effectively as a portable air purifier can clean a room.
Compared with the cheapest basic filters available, medium-efficiency MERV filters like the Nordic Pure MERV 12 can greatly reduce airborne dust, mold spores Nordic pure Coupon, pollen, and even smoke, and doing that can help ease respiratory ailments, according to an NIH review.
However, these filters have a few drawbacks—first, they usually cost significantly more than basic fiberglass filters. You’re supposed to replace filters every few months, so the cost adds up. Second, they can put stress on some HVAC equipment, making the system less effective at heating and cooling, potentially even shortening its lifespan by restricting airflow and forcing the equipment to run harder. But those are rare circumstances, and the decision to pay more for a better filter or not mainly comes down to whether or not cleaner air is a priority for you. If it is, there are several examples of qualified filters that we’d recommend—including the Nordic Pure MERV 12, a perfectly good filter that we’d look for first (because it often costs less), as well as two other filters that are also fine.
Who this is for
Most HVAC systems use a standard 1-inch-thick filter, so we focused exclusively on 1-inch medium-efficiency MERV filters. These are installed either in wall-mounted air-return vents (most common in the South), or at the air handler (more common in the Mid-Atlantic and northern states, where the air handler is often placed in the basement, near the furnace). A correctly sized 1-inch MERV filter simply rests behind a bracket at the return register; if you’re not sure what size you need, check the narrow side of an existing filter for the dimensions (like “16 x 25 x 1”).
If your HVAC system uses a thicker filter (usually in the 4- to 5-inch range, and usually mounted at the air handler), it was likely designed specifically for medium-efficiency MERV filtration. You don’t need our advice; simply replace the existing filter with one that has the same specs.
What is a MERV rating?
MERV stands for Minimum Efficiency Reporting Value, and is a measure of how well a filter removes particulates from the air. In that way it’s akin to the more familiar HEPA rating used on air purifiers. And like the test for HEPA rating, MERV testing measure a filter’s efficiency—the percentage of particles it captures—in a single pass. Air is loaded with particulate matter, sent through the filter a single time, and the results measured. In real-world use, with the air in your home constantly recirculating through the ducts and passing through the filters each time, the cumulative effect of the filters rises.
How to choose a filter by its MERV rating
To decide what filter we’d buy, we needed a more pragmatic explanation of MERV, so we turned to Kathleen Owen, a research engineer specializing in air filtration. Owen almost literally wrote the book on MERV: In the 1990s she helped define the American Society of Heating, Refrigeration, and Air-Conditioning Engineers’s ASHRAE 52.2 standard that’s used to set the ratings. She later chaired the ASHRAE 52.2 committee, which regularly updates the standard to address changes in filter technology.
In a conversation about the most common filter levels for sale at retail, MERV 1 through 16, Owen said this range “gets you from filters that might catch a golf ball—I’m exaggerating a little bit—up to filters that will catch almost everything.” Owen added, “I like to tell people that each of those filters has a purpose.”
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