22 Inch Wide Window Air Conditioner

Nigh HVAC systems utilise a standard 1-inch-thick filter, and so we focused exclusively on ane-inch medium-efficiency MERV filters. These are installed either in wall-mounted air-return vents (well-nigh common in the South), or at the air handler (more than mutual in the Mid-Atlantic and northern states, where the air handler is often placed in the basement, almost the furnace). A correctly sized one-inch MERV filter merely rests backside a subclass at the return register; if you’re not sure what size y'all demand, check the narrow side of an existing filter for the dimensions (similar “sixteen x 25 ten one”).

If your HVAC arrangement uses a thicker filter (usually in the four- to 5-inch range, and commonly mounted at the air handler), it was probable designed specifically for medium-efficiency MERV filtration. You don’t need our communication; only supersede the existing filter with ane that has the same specs.

MERV stands for Minimum Efficiency Reporting Value, and is a measure out of how well a filter removes particulates from the air. In that way it’south akin to the more than familiar HEPA rating used on air purifiers. And like the test for HEPA rating, MERV testing measure a filter’s efficiency—the per centum of particles information technology captures—in a single laissez passer. Air is loaded with particulate matter, sent through the filter a unmarried fourth dimension, and the results measured. In real-globe apply, 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.

But MERV is different in some primal means. Beginning, instead of being a simple pass-fail measure like HEPA (a filter is either HEPA-rated or it’due south not), MERV ratings fall on a scale from ane to 16, with higher numbers indicating better functioning.

Too different HEPA, MERV tests measure out particulates of dissimilar sizes, from 0.3 micron (very small and difficult to filter—the size HEPA tests measure) upwardly to 10 microns (relatively large and easy to filter). MERV too doesn’t have a target percentage for removal, the way HEPA does. Instead, the actual per centum removal is recorded for each of 12 particle sizes, and these numbers are referenced against a functioning tabular array to determine the appropriate rating.

So when you look at the full spectrum of what’s floating effectually in the air in your firm, MERV ratings reflect a filter’s performance on all of it. Higher numbers indicate a better filtration of the smaller particles, similar pollen and smoke, that cause many respiratory issues. And medium-efficiency MERV filters in the viii to 13 range—the kind we would get—can remove 90 percent or more of these. (For a actually thorough caption of how MERV ratings are calculated, visit the website of the National Air Filtration Clan.)

1 more thing: Some companies, including major filter manufacturer 3M/Filtrete and major filter retailer Domicile Depot, apply their own rating conventions (MPR by Filtrete and FPR by Abode Depot). Both claim to be based on the American Society of Heating, Refrigeration, and Ac Engineers’s ASHRAE 52.2 standard that’s used to set MERV ratings, but neither company provides an easily accessible explanation of how its own ratings differ from or compare with MERV. (Filtrete does impress MPR and MERV equivalents on the frames of its filters, just yous tin’t see that until y'all’ve actually got i in your easily.)

After we inquired, Filtrete replied that its MPR filters capture more than of the very small particles (0.3 to i micron) than equivalent MERV-rated filters when tested to ASHRAE 52.2 protocol, and shared a test summary that backs this upwards; on the larger particles (one to 10 or more than microns), MERV and MPR operation was nearly identical. Filtrete said MPR 1900 is equivalent to MERV 13, MPR 1500 to MERV 12, and MPR g to MERV xi.

Dwelling house Depot shared a basic comparative chart but no test data or protocols; it equates FPR 9 and ten to MERV 12, FPR seven and 8 to MERV 11, and FPR half dozen to MERV 10.

To determine what filter we’d buy, we needed a more pragmatic caption of MERV, so we turned to Kathleen Owen, a research engineer specializing in air filtration. Owen virtually literally wrote the volume on MERV: In the 1990s she helped ascertain the American Social club of Heating, Refrigeration, and Air-conditioning Engineers’southward ASHRAE 52.2 standard that’s used to set up the ratings. She later chaired the ASHRAE 52.2 committee, which regularly updates the standard to address changes in filter applied science.

In a conversation about the nigh mutual filter levels for sale at retail, MERV 1 through xvi, Owen said this range “gets you lot from filters that might take hold of a golf game ball—I’m exaggerating a trivial fleck—up to filters that will grab almost everything.” Owen added, “I like to tell people that each of those filters has a purpose.”

• MERV i to 4 (and unrated): Filters like the MERV 4 E-Z Flow, MERV two True Blue, MERV 1 Filtrete Basic Cut-To-Fit, and the unrated Flanders, are the cheapest (some nether $i apiece) and most bones MERV-rated filters. Their purpose is to keep particles larger than 10 microns—including pet hair (but not dander), rug fibers, and heavy dust—from clogging the heating/cooling coils and ducts in your HVAC system. They accept fiddling to no touch on fine particulates like pollen and smoke, so they will non practice much to ease respiratory issues. Merely even with their limitations, these filters aren’t pointless. They prolong the life of your equipment and help continue information technology running efficiently in the heating and cooling seasons. “Think of how important your screen door is in summer when in that location’s flies out,” Owen said. If you are reading this guide, you probably intendance too much nigh air quality to consider one of these filters, but if you’re living (or vacationing) in a rental and don’t want to invest much—especially if the existing filter is problematically old or dirty—replacing it with a MERV one to 4 filter would be a fine quick set up.

• MERV v to 7:
Owen said filters in this range (similar this MERV 7 Nordic Pure) were created equally an improvement on the basic MERV i to 4 filters and designed to also filter out midsize particles (3 to 10 microns, which includes near pollen and mold spores) that could encourage mold growth on heating/cooling coils. These filters are non as widely sold as the lower and college MERV-rated filters in hardware stores, simply they tin can be plant online easily. There’due south null wrong with these types of filters; we only didn’t focus on them as much every bit we did those in the 8 to xiii range mostly because this class, past comparing, usually isn’t any cheaper, doesn’t perform quite as well, and often isn’t as easy to find.

• MERV 8 to 13: This is the category we’d recommend for people who care about indoor air quality, and there are many equally adept examples, such as the Nordic Pure MERV ten and MERV 12, the Honeywell FPR 9, and the Filtrete 1500. (For more than detail on these models, encounter the A perfectly skilful HVAC filter and Ii other filters that are also fine sections.) We focused on filters in the MERV 8 to 13 range because they are good to fantabulous at removing fine particulates (every bit pocket-size as 0.three to 3.0 microns in diameter, including fume and exhaust particles and leaner), plus annihilation larger. This MERV range, Owen said, “covers most of the stuff that people are likely to breathe in unless they’re actually shut to the source.” The EPA says filters rated MERV vii to 13 “are likely to be near equally effective as true HEPA filters at controlling about airborne indoor particles.” The higher end of the range, MERV 11 to 13, removes 20-plus to fifty-plus percent of the very smallest, 0.3-to-1.0-micron particulates, and filters in this range are especially popular. An NIH literature review indicates that filters in this range can significantly reduce indoor fine-particulate pollution and convalesce some respiratory ailments.

• MERV 14 through xvi:
These are specialized filters that require a purpose-congenital HVAC system; they’re widely used in hospitals and some commercial and industrial environments, simply mostly not in homes.

So why doesn’t anybody get a MERV 8 to 13 filter? Beyond their higher price, there is as well a concern your equipment might not exist able to handle them, co-ordinate to engineers we interviewed from two of the major HVAC manufacturers: Jay Ayers of Trane and Doug Powell of Carrier. They (and Owen) all told us MERV filters in this range restrict airflow more than than low-MERV filters, as measured past the drib in air pressure the filters create when installed. That can potentially strain your equipment.

Powell noted that, “You accept a fair amount invested in your HVAC system, and unless you know how much pressure drop you have in it and how much more it can handle, you could end up shortening the life of your blower. And a blower’s not cheap.” Ayers said, “That’south the danger of looking at one-inch filters and trying to become college-efficiency and do the job that’south needed for allergies: You run the run a risk of really damaging your blower and your HVAC system.” (If you are concerned about this, to be absolutely punctilious you can hire an HVAC firm to measure pressure driblet in your arrangement.ⁱ)

Confronting these warnings, yet, is a mountain of possessor testimony that MERV eleven, 12, and even 13 filters accept worked just fine in their systems for years. As well, an frequently-cited comprehensive independent test of MERV 8 to 13 filters’ furnishings on HVAC airflow and free energy consumption (a proxy for how hard the equipment is working) concluded that even “if no accommodations are made for the greater pressure level drop of high-MERV filters, air flow and energy penalties are non likely to exist severe—at to the lowest degree, not until the filter is loaded with dirt.”

We feel the manufacturers’ concerns are a bit overcautious, in part considering a recent innovation in air filters permits loftier MERV ratings (11 to xiii) with depression pressure drop.ⁱⁱ
So-called electret filters use a mat of fibers that are electrostatically charged. The charge helps concenter airborne particles (rather than just passively impeding them). As a result, the mat can be more than porous, causing amend airflow and a smaller force per unit area drop. However, Owen emphasized, electrets become less efficient over fourth dimension, often significantly so. “Electret media will drop in efficiency upon employ, sometimes by as much equally 50 percent,” she said. “Basically what happens is the tiny particles—nosotros’re talking 40, 50 nanometers, which there are gazillions of in the air—will glaze the charged fibers and keep them from alluring larger particles.” That means regularly replacing electrets is absolutely key to maintaining good filtration, and most come with lx- or 90-day replacement schedules. If you run your system yr-round, that’southward potentially six filters a yr.

Given all this, we decided that if we were buying new filters today, nosotros’d await for an electret filter around the MERV 8 to thirteen level with a low pressure level drop that was both affordable and like shooting fish in a barrel to observe.

Nordic Pure’due south MERV 12 filters are not the just products that meet all our criteria, just they are perfectly good examples, and they’re usually competitively priced and easy to discover online. We like that they’re genuinely MERV-certified, because unlike the proprietary ratings used past some bigger-proper noun brands, the MERV criteria are publicly available. Beingness rated MERV 12, the Nordic Pures will remove at least 35 percent of particles in the 0.3-to-1.0-micron range, which includes leaner and smoke; at least 80 percent of 1.0-to-3.0-micron particles, which include fine dust and soot; and at least 90 percent of larger pollen, grit, pet pilus, and lint particles. Again, MERV stands for Minimum Efficiency Reporting Value, so this is the worst performance measured during 3rd-party testing to the ASHRAE 52.2 standard. And once more: the MERV examination measures a single laissez passer of polluted air through the filter. In your home, the air will continuously recirculate when your HVAC system is, leading to cumulatively greater filtration with each trip through the render registers.

Nordic Pure filters are by and large sold online, and the MERV 12s typically retail for a much lower price than competitors—nearly $40 for a six-pack of sixteen-by-25-by-1-inch filters, or about $7 each (with some competitors you lot’ll pay about double that price for MERV 11/12 or the equivalent). At the recommended three-month replacement bike, a Nordic Pure tin can relieve you lot well-nigh $30 to $40 a year.

Nordic Pure reports the filter’s force per unit area drop as 0.24 inch, which puts it a shade higher than the similar, MERV 12–equivalent Filtrete 1500 at 0.22 inch. But most people seem to accept had no issues with the Nordic Pures straining their HVAC organisation—the six-pack has an overall score of 4.iii stars (out of five) across more ii,800 reviews at Amazon at this writing (we should note that the reviews once received an A rating from Fakespot; equally of May 2019 that rating was downgraded to a C). The Nordic Pure MERV 12 filters are bachelor in many sizes, so yous should be able to notice ane that fits your return vent opening.

If you tin can’t detect Nordic Pure in your size, or if you prefer to buy and pick up a new filter in a store immediately, Honeywell’southward FPR 9 filters and Filtrete’s MPR 1500 filters are similar, and they’re widely bachelor at retail. (Habitation Depot stocks Honeywell; Lowe’s and Ace stock Filtrete). These filters perform on a similar level as the Nordic Pure MERV 12, they are well-reviewed by many owners, they come up in a wide range of sizes, and the high likelihood that they’re in stock at a nearby hardware shop is a big advantage if you need one ASAP.

We don’t honey that neither Honeywell or Filtrete is MERV-certified, but their proprietary ratings are reportedly equivalent to MERV 11 or 12. We couldn’t observe pressure-driblet information on the Honeywell, so that’south a possible concern. The Filtrete’s pressure drop is 0.22 inch, fractionally lower than the Nordic Pure MERV 12’s at 0.24 inch. Information Filtrete shared with us indicates the the 1500 removed 54 percent of 0.3-to-one-micron particles in its ain tests, versus a minimum of 35 percent for the MERV 12-certified Nordic Pure. On larger particles, the two filters performed very similarly.

A major reason nosotros’d look for Nordic Pure equally an pick start comes down to price: Both the Honeywell and Filtrete options usually price more than twice the toll of the Nordic Pure filters. As electret filters, all these models will lose effectiveness as they capture particles, and should be replaced at least every 3 months, per the manufacturers’ recommendation. But homes with sure challenging conditions—if y'all smoke, frequently use candles or fireplaces, or accept pets—will significantly reduce that lifespan.³

Owen also offered a simple way to guess if it’s time for a bandy: “If you tin can go to your filter easily, one simple thing you tin can do is only go accept a look. If you tin can’t come across the filter media anymore, it’due south been in there as well long. Change it!”

During a wildfire, you’ll need to change your filters more ofttimes than you would nether normal air atmospheric condition, and there are a few indicators that tin can help you know when information technology’south fourth dimension to replace one.

We asked Kathleen Owen, the filtration skillful we spoke with for this guide, for her advice. She replied in an email: “If I lived well-nigh the wildfires and didn’t find the cost prohibitive, I’d probably modify a 3-month filter every month during the flavour. Or possibly after each major event— say if a fire gets close enough to be a big deal (rather than simply you know about it from the news).”

Owen also noted that wildfire smoke is a complex mixture, incorporating both physical fume particles (which filters trap permanently) and water vapor and volatile organic compounds (gases), which are not trapped—and the latter of which create the smoky olfactory property. “The wet particles or ones with gases adsorbed on them can be collected, then requite off the smelly stuff the side by side fourth dimension the fan comes on,” she wrote. “So, 1 recommendation is that if folks feel like the air breathes easier or smells OK with the HVAC on only are gagging in the first infinitesimal or two the HVAC is on again, irresolute the filter could help.”

In that location are also visual cues you can look for when judging whether to replace your furnace filter, Owen wrote. Bottleneck increases the pressure differential between the intake and outflow sides, and this tin cause the filter’due south pleats to flatten out or the frame of the filter to buckle. Both are evidence that the smoky air is finding a path around the chock-full filter rather than through it, and that it’due south time to install a new one.

In addition to obvious steps like keeping windows and doors closed, Owen also brash shutting off bathroom fans and range hoods, both of which vent directly to the outside and, as a result, draw an equal volume of smoky outdoor air in through window frames and other leaky spots.

Owen added that she’d also consider adding a portable air purifier with a VOC filter. All our purifier picks have them, and though in our tests against an extreme load of ethanol vapors we found most of them ineffective, anecdotally we tin say that they seem to perform well nether fairly heavy fume weather condition. Both in guide author Tim Heffernan’southward apartment and in our New York examination space, after running our top picks for a few hours, in that location was little olfactory evidence that hundreds of matches had been burned nearby.

Finally, Owen noted that the American Society of Heating, Refrigeration, and Air conditioning Engineers (ASHRAE) has begun working on building-filtration guidelines specific to wildfire weather condition. We’ll be following up on this equally it develops. For more on this topic, delight run into our reporting on how to clean wildfire smoke from your home.