Higher is not always better. Check what your filter slot and blower can carry before you buy a year’s supply.
MERV 13ceiling on the defaults: 20×25×1, MERV 8, PSC blower, cooling coilEPA recommends "at least a MERV 13 rating, or as high a rating as your system fan and filter slot can accommodate". This screen checks the second half of that sentence, and never issues MERV 14 to 16 without a measurement.
The short answer
Most homes can use up to MERV 13, which EPA recommends if your system fan and filter slot can take it.
A typical 20×25×1 slot gets MERV 13 at moderate risk; a small slot drops to MERV 11.
Ice on the coil, a furnace cutting out early or a bowed filter means stop: the system is already short of air. A static pressure test settles it.
What can your filter slot carry?
Seven things you can read off the filter and data plate. No pressure drop is estimated. Nothing is emailed.
—What to do
—Highest MERV this screen will issue
—Your filter face, in context
—Restriction risk band
—The question to ask a contractor
What this assumed
—
A screen, not a pressure calculation: field measurements span 16 to 173 Pa inside one MERV band. Only measured static pressure against your equipment’s rated maximum settles it. Equipment, duct and gas work is licensed work. HyreHVAC sells no filters and recommends no brand.
How do you read the filter result?
The ceiling is the highest MERV this page will suggest for your inputs. The restriction risk band says how much weight that suggestion can bear. The question to ask is the same on every result, because only one measurement settles this.
HyreHVAC analysis: the bands do not grade your system. They show how far a guess can go before it runs out. On a high-risk result, the honest move for a screening tool is to stop.
What do the three risk bands mean?
Low or Moderate: the ceiling is usable
Little or nothing in your inputs argues against an upgrade. Buy one filter at the ceiling, fit it, and watch for two weeks: registers, run times, noise at the return, and in summer the refrigerant line outside. If nothing gets worse, you have your answer.
On Moderate, mention the factors to a technician next visit. It is not a reason to wait.
Elevated: measure before adding resistance
Several factors stack up, often a shallow slot, a small face, a fixed-speed blower and a cooling coil. The ceiling drops to MERV 11, still the first rung ASHRAE 52.2 tests below one micrometer, so it is a real gain.
Next, get the measurement, not a new filter: total external static pressure, filter pressure drop, and the rated maximum from your manual.
High, or any hard symptom: stop
Ice on the coil, a furnace tripping its high-limit switch, or a collapsing filter mean the system is short of air now. More filtration adds resistance to a system that has none left.
The useful next step: fit the least restrictive filter the slot takes, make sure no return grille is blocked by furniture or a rug, and have the system checked. Filtration comes after the system can breathe.
What does a MERV rating actually measure?
The minimum each MERV rung must reach, smallest particles against largest. MERV 10 and below are plotted at zero for E1 because the standard sets no requirement there.HyreHVAC chart of ANSI/ASHRAE Standard 52.2 Table 12-1, from Addendum d to Standard 52.2-2017, retrieved September 5, 2026.
MERV comes from ANSI/ASHRAE Standard 52.2, a lab test. The filter is tested against particles from 0.30 to 10 micrometers, and the results are grouped into three averages: E1 for 0.30-1.0 µm, E2 for 1.0-3.0 µm and E3 for 3.0-10 µm.
Table 12-1 of the standard then sets the minimum each average must reach at each MERV rung.
MERV is a floor, not a score. A MERV 11 filter met the MERV 11 minimum in all three ranges. It may beat the minimum easily in one and barely pass in another. The rating cannot tell you which.
MERV 1 through 10 have no E1 requirement at all. A MERV 8 filter passed without anyone testing it against particles under 1 micrometer, the size of most health concern. MERV 11 is the first rung that asks, at 20%. MERV 13 asks for 50%.
HyreHVAC analysis: “MERV 8 is fine for most homes” and “MERV 13 for smoke” answer different questions. Below MERV 11 the rating covers dust, lint and pollen. From MERV 11 it covers fine particles too. For smoke or small allergens, going from 8 to 11 is the first real step.
MERV says nothing about how hard the filter is to breathe through. Two MERV 13 filters of the same size can differ in resistance more than a MERV 8 and a MERV 13 do. That is why this page is a screen, not a calculator.
What does each MERV rating require?
MERV
Range 1: 0.30 to 1.0 µm (E1)
Range 2: 1.0 to 3.0 µm (E2)
Range 3: 3.0 to 10 µm (E3)
Average arrestance
MERV 1
no requirement
no requirement
< 20%
< 65%
MERV 2
no requirement
no requirement
< 20%
≥ 65%
MERV 3
no requirement
no requirement
< 20%
≥ 70%
MERV 4
no requirement
no requirement
< 20%
≥ 75%
MERV 5
no requirement
no requirement
≥ 20%
–
MERV 6
no requirement
no requirement
≥ 35%
–
MERV 7
no requirement
no requirement
≥ 50%
–
MERV 8
no requirement
≥ 20%
≥ 70%
–
MERV 9
no requirement
≥ 35%
≥ 75%
–
MERV 10
no requirement
≥ 50%
≥ 80%
–
MERV 11
≥ 20%
≥ 65%
≥ 85%
–
MERV 12
≥ 35%
≥ 80%
≥ 90%
–
MERV 13
≥ 50%
≥ 85%
≥ 90%
–
MERV 14
≥ 75%
≥ 90%
≥ 95%
–
MERV 15
≥ 85%
≥ 90%
≥ 95%
–
MERV 16
≥ 95%
≥ 95%
≥ 95%
–
Minimum average removal efficiency at each rung. From ANSI/ASHRAE Standard 52.2, Table 12-1, as printed in Addendum d to Standard 52.2-2017 (published May 30, 2025), retrieved September 5, 2026.
Read the “no requirement” cells first. Ten of the sixteen rungs promise nothing about particles under one micrometer. MPR and FPR numbers on some boxes are makers’ own scales and have no published conversion to MERV.
Why isn’t a higher MERV filter always better?
Because a tighter filter can cut airflow, and airflow is what moves heat in and out of your system.
Measured pressure drop across the filter in 10 homes, the owner’s filter against a MERV 16 filter in the same slot.HyreHVAC chart of figures in Walker, Faulkner, Dickerhoff and Turner, “Energy Implications of In-Line Filtration in California Homes” (LBNL for the California Energy Commission, CEC-500-2013-081), retrieved September 5, 2026.
EPA says: “Not all HVAC system fans can accommodate high-efficiency filters without affecting system performance. Existing residential HVAC systems may not have enough fan or motor capacity to accommodate higher pressure drop filters without reducing airflow to the point where cooling or heating capacity is lost or good air mixing is sacrificed.”
EPA goes on: “These shortcomings can lead to increased risk of component failure and/or comfort problems in the space.”
EPA adds: “Simply installing a high-efficiency filter is no guarantee that it will work as intended.”
A blower is built to move a set airflow against a set resistance. The ducts, coil and filter each take a share. Add resistance at the filter and, on most home equipment, airflow drops.
Airflow over the cooling coil carries heat into the refrigerant. Airflow over the furnace heat exchanger carries heat out. Cut it, and the problems are specific and expensive.
The field study: ten California homes were monitored for at least a year each. The filters the owners had fitted, MERV 4 to 13, measured 16 to 173 Pa of pressure drop, averaging 71 Pa.
With MERV 16 filters in the same slots, the range became 16 to 300 Pa, averaging 149 Pa. The report says MERV 16 “almost doubled the pressure across the filter”. In one home it rose more than tenfold.
Airflow followed. Systems with fixed-speed PSC blowers lost 188 cfm on average (22%). Variable-speed BPM systems lost 178 cfm (15%), mostly in two systems already at full blower output. Two households pulled the MERV 16 filter within days because of the noise.
HyreHVAC analysis: look at the lowest row of the chart. One home’s pressure drop did not change at all with MERV 16, because its slot had the depth and face area to absorb it.
The restriction belongs to the whole filter slot, not the number on the box. So we publish no pressure drop for any MERV rating.
What happens when a filter restricts airflow?
What happens
Why
What you would notice
Cooling capacity drops
Less air over the coil carries less heat. The LBNL report says AC performance falls fast below about 200 cfm per ton, and systems near that limit “may be pushed over the edge” by a tighter filter.
The house takes longer to cool on hot days, or never gets there on the hottest
The indoor coil freezes
With too little warm air, the coil drops below freezing and moisture turns to ice. The ice blocks more air, so it gets worse.
Ice on the indoor coil or the copper line outside; a system that runs nonstop and cools nothing; water when it thaws
Liquid refrigerant reaches the compressor
A starved coil cannot boil off all the refrigerant, so some returns as liquid to a compressor built for vapor.
Nothing, until the compressor fails: the most expensive single failure
The furnace trips its high-limit switch
Too little air carries heat away from the heat exchanger, so it overheats until a safety switch cuts the burner.
Heat that shuts off before the house is warm, then restarts; rapid cycling on cold nights
Heat exchanger stress
Repeated overheating puts the exchanger through heating and cooling cycles it was not designed for.
Nothing visible. That is why a furnace that keeps tripping its limit needs a service call
Air slips around the filter
As pressure rises, more air takes the easy path around the frame. EPA notes this from poor fit and from a loaded filter.
A filter clean at the edges and dirty in the middle, or bent in its track
Blower energy and noise
A variable-speed blower holds airflow by working harder. In the study, MERV 10-13 changed blower energy by less than 5%; MERV 16 reached about 20% in the worst simulated case.
Whistling or roaring at the return grille, and a slightly higher bill
The first four rows cost money. The last three are what you notice first.
HyreHVAC analysis: this is no argument for a dirty or low-MERV filter. It is an argument for matching the filter to the slot, and finding out what your system can carry before you buy a year’s supply.
What do the filter terms mean?
If you can use the first two in a sentence, you will have a better talk with whoever measures your system.
Static pressure, and external static pressure (ESP)
The resistance the blower works against, in inches of water column. ESP is the part outside the equipment: ducts, coil, filter. Every air handler has a maximum ESP in its installation manual. That is the budget your filter spends from.
What field studies measure
Studies summarized in the LBNL report found about 0.5 in. of water for heating-only systems and 0.8 in. with a cooling coil. The DOE furnace test assumes 0.20 to 0.23 in. Neither is your equipment’s rated maximum, so do not use either as a target.
Face area, and face velocity
Face area is the filter’s width times height. Face velocity is how fast air moves through it. Double the area at the same airflow and air moves half as fast, so resistance falls sharply. The ten study homes ranged from 196 sq in (14×14) to 720 sq in (20×36).
Media area, and why depth matters
Pleats give a filter far more media than its face. EPA says deeper pleated filters, 4 to 12 inches, “increase the area of the filtration medium and limit the airflow resistance”. The study found 4-inch MERV 16 filters less restrictive than 1-inch ones.
PSC and BPM/ECM blowers
A PSC motor runs at one speed and delivers less air as resistance rises: 188 cfm (22%) lost on average with MERV 16. A variable-speed BPM or ECM motor speeds up to hold airflow, paying in power and noise, until it hits maximum output.
Cfm per ton
Airflow in cubic feet per minute per ton of cooling. The LBNL report says AC performance falls fast below about 200 cfm per ton. It shows why a filter choice is also a capacity choice.
Electret media
Fibers with a built-in electrostatic charge that attracts particles. EPA says these “can have higher MERV ratings without an increased airflow resistance”. EPA also notes they can lose efficiency as they load, because the charge fades.
Bypass
Air going around the filter instead of through it: past a loose frame, a leaky return, or a bent filter. Bypass rises as the filter loads, so it filters least when it restricts most.
Ask for numbers, not adjectives. “Your ductwork is undersized” is an opinion. “Total external static pressure 0.94 in. w.c. against a rated maximum of 0.50” is a measurement you can hand to the next person.
Where do you find each input?
Filter width and height, in inches
Printed on the cardboard edge of your current filter, like 20 × 25 × 1. Enter the first two. If nothing is printed, measure the frame.
Use the size on the box. The filter itself is slightly smaller so it slides in.
Filter depth
The third number on the edge. One inch is most common in older homes. Four- and five-inch filters sit in a media cabinet on the air handler, with a door about a foot wide.
A filter behind a wall or ceiling return grille is almost always one inch. That is also where a bigger face is easiest to get.
MERV currently fitted
On the box and usually the filter edge. MPR and FPR are makers’ own scales with no published conversion, so choose “not printed” instead of guessing.
A thin fiberglass panel you can see light through is a low rung, typically MERV 1 to 4.
System type
A gas or oil furnace with a cooling coil above it is the most common ducted setup in the US. A heat pump air handler has no burner or flue. With no ducts or central filter slot, choose ductless and the screen will say it does not apply.
This input decides whether a cooling coil is in the air path: roughly the gap between 0.5 and 0.8 in. w.c. in the systems surveyed.
Blower type
Named on the data plate or in the manual as “PSC” or “variable speed”, “ECM” or “BPM”. If the blower ramps up and down instead of switching on at one speed, it is variable speed.
“Not sure” is treated as the less forgiving type, the safer way to be wrong.
Any sign of restriction
The most important input, and the one people skip. Ice on the coil, a furnace cutting out early, a whistling return or a filter sucked into its track all say the same thing: the system is short of air.
If any is present, the screen stops recommending and tells you what to fix.
How does the filter screen work?
The steps below are exactly what runs. It is a screen, not a physics model, and every weight is our own judgment.
1
Start the ceiling at MERV 13
That is EPA’s recommendation: “at least a MERV 13 rating, or as high a rating as your system fan and filter slot can accommodate”. The rest of the screen checks the second half of that sentence.
2
Add restriction points
Depth: 1 inch +2, 2 inch +1. Face: under 250 sq in +2, under 400 +1, 720 or more −1. PSC or unknown blower +1. Cooling coil +1. Already MERV 13+ +1. Weak airflow or noise +2, bowed filter +3, ice or limit tripping +4.
3
Band the total
0-2 Low, 3-4 Moderate, 5-6 Elevated, 7 or more High. The band says how much confidence a screen with no measurement can carry, not how bad your system is.
4
Apply the stops
A hard symptom drops the ceiling one rung below what is fitted and says “do not raise MERV”. High caps at MERV 11 or the current rating, whichever is lower. Elevated caps at MERV 11. It never issues MERV 14, 15 or 16.
5
State the gain from the standard
The gain in the verdict is read straight from ASHRAE 52.2 Table 12-1: the change in the minimum E1 requirement between the fitted and proposed rungs.
6
Estimate no pressure drop
There is no pressure term. Field measurements span 16 to 173 Pa within one MERV band, so any number would be made up.
What should you check before buying a higher MERV filter?
Find your equipment’s rated maximum external static pressure
It is in the installation manual, usually a free PDF from the maker by model number. It is the one figure that makes the question answerable.
Get static pressure measured, both sides of the filter
A technician with a manometer measures total pressure across the air handler and the drop across the filter alone. It takes minutes. Get both in writing, in inches of water column.
Ask whether the returns are the real limit
DOE’s review found low airflow in more than 50% of systems before any filter change. If small or leaky returns are the cause, a higher-MERV filter will make it worse.
Look for a bigger face or deeper slot before a higher number
A 4- or 5-inch media cabinet, or a second return with its own filter, makes room for a higher MERV. It costs more than a filter and less than a compressor.
Buy one filter, not a case, and watch for two weeks
Problems show up fast: weak registers, longer run times, noise at the return, ice, a limit trip. One filter is a cheap test.
Do not tape or stuff the filter track
If air gets around the filter, the frame or ducts need fixing by someone qualified. On a gas furnace, the air path is a safety matter.
Do not treat MPR or FPR as MERV
They are makers’ own scales, with no published conversion. EPA lists them as separate metrics.
Do not adjust the blower to compensate
Changing blower speed settings is licensed work on equipment with line voltage and, on a furnace, a burner. This page is not instructions for it.
What changes the filter recommendation most?
1. A symptom already present
Nothing else comes close. Ice on the coil or a furnace tripping its limit overrides every other input and turns the result into a stop sign.
2. Filter depth
The biggest thing you can change. EPA and the field study agree: deeper media means less resistance. It usually means fitting a cabinet, which is what makes a high MERV safe.
3. Face area
A 14×14 filter and a 20×36 filter differ 3.7 times in opening size, and both were found in the ten study homes. Few homeowners or installers ever revisit it.
4. Blower type
It changes how the system pays for resistance, not whether it exists. PSC pays in lost airflow. Variable speed pays in power and noise, then in airflow once it runs out of speed.
5. What is left out on purpose
Any pressure drop figure, since the spread in one MERV band is over tenfold. Duct size, duct leaks and coil condition, which matter more than the filter. Airflow in cfm, which no homeowner has. And price, brand and product: we sell nothing.
HyreHVAC analysis: adding those would make the tool look more authoritative and be less true. It is built to stop where a real measurement takes over.
What mistakes do people make with HVAC filters?
Buying the highest number on the shelf
In the field study, fitting MERV 16 blind roughly doubled filter pressure, cost PSC systems 22% of their airflow, and two households rejected it within a week for noise.
Assuming MERV 8 is “medium”
It sits halfway up a 16-rung scale, but the standard asks nothing of it below one micrometer. For smoke or fine particles, MERV 8 has not been asked the question.
Leaving a high-MERV filter in too long
Resistance and bypass both rise as a filter loads. An overdue high-MERV filter is worse than a lower one changed on time.
Reading a maker’s rating as MERV
MPR numbers run into the thousands and FPR into the hundreds. They are a different scale with no published conversion.
Removing the filter to fix weak airflow
It works briefly, then dust coats the indoor coil and blower wheel. A dirty coil is a worse restriction. Fit the least restrictive filter the slot takes instead.
Expecting a filter to clean a house when the fan is off
A central filter only works while the fan runs. If the system sits idle in June, it filters nothing.
Accepting “your system can’t handle MERV 13” without a number
It may be true, but it cannot be checked without a manometer. Ask for the measured static pressure and the rated maximum.
What does this filter tool not know?
The filter selector reads six things you can see and says whether a higher MERV is worth trying. It is not a model of your system.
Your airflow. Without cfm it cannot work out face velocity, which drives pressure drop.
Your ducts. Small returns, leaky return ducts and a dirty coil can take more of the pressure budget than the filter, and a form cannot see them.
Your equipment’s rated maximum static pressure. The one figure that makes this answerable. It is in your installation manual.
Pressure drop. Across ten homes, one MERV band spanned 16 to 173 Pa. Any single figure would be an average of other houses.
Whether a filter is the right fix. For one room with a specific problem, a portable air cleaner is often better than more resistance in ducts the whole house needs. See indoor air quality services.
It is not an instruction to do work. Measuring pressure, fitting a cabinet, changing ducts or blower settings, and anything with gas or line voltage is licensed work.
HyreHVAC does not install, service or sell HVAC equipment, and holds no data on quotes, invoices or finished jobs. Nothing here is a price we observed.
That is also why these tools can tell you to keep the system you have.
What does a worked filter example look like?
Step
What happens
Result
The house
A 1990s two-story house with a gas furnace and a cooling coil. One 20 × 25 × 1 filter at the furnace, MERV 8. A PSC blower. No complaints.
The defaults on this page
1. Face area
20 × 25 = 500 sq in, inside the 196 to 720 sq in range of the ten study homes. Neither good nor bad.
500 sq in, no points
2. Depth
One inch: the most restrictive common size, still noisy and flow-limiting at high MERV in the study.
+2 points
3. Blower
PSC. Add resistance and airflow simply drops. The study measured 188 cfm (22%) lost on PSC systems with MERV 16.
+1 point
4. System
A cooling coil is in the air path, already using part of the pressure budget.
+1 point
5. Symptom
None. This input would have overridden everything else.
+0 points
6. Band
4 points total: Moderate. A couple of factors worth naming, nothing disqualifying.
Moderate restriction risk
7. Ceiling
Nothing argues against EPA’s MERV 13, so it stands. The screen never issues MERV 14 to 16.
MERV 13, not higher, until measured
8. What that buys
From ASHRAE 52.2 Table 12-1: MERV 8 has no requirement for 0.30-1.0 µm particles; MERV 13 must catch at least 50% of them.
The system’s first real fine-particle filtering
9. Next step
Buy one MERV 13 filter, not a case. Watch registers and run times for two weeks. Ask for static pressure at the next service visit.
One filter, one measurement
HyreHVAC calculation: each step is the screen running on the page defaults. The point weights are ours; the MERV thresholds are ASHRAE 52.2; the airflow figures are the LBNL field study.
No pressure drop appears, because none was calculated. The system has the headroom or it does not, and one manometer reading answers that for good.
How does each input change the result?
What changes from the defaults
Ceiling issued
Restriction risk
Defaults: 20×25×1, MERV 8, furnace with coil, PSC blower, no symptom
MERV 13, not higher, until measured
Moderate (4 points)
Depth: a 4 in media cabinet instead of 1 in
MERV 13, not higher, until measured
Low (2 points)
Depth: a 5 in media cabinet
MERV 13, not higher, until measured
Low (2 points)
Blower: variable-speed ECM instead of PSC
MERV 13, not higher, until measured
Moderate (3 points)
Face: 14×14 instead of 20×25
MERV 11, not higher, until measured
Elevated (6 points)
Face: 20×36 instead of 20×25
MERV 13, not higher, until measured
Moderate (3 points)
System: furnace only, no cooling coil
MERV 13, not higher, until measured
Moderate (3 points)
System: heat pump with an air handler
MERV 13, not higher, until measured
Moderate (4 points)
Current filter: MERV 13 already fitted
MERV 11 — below the MERV 13 fitted now
Elevated (5 points)
Current filter: nothing printed on it
MERV 13, not higher, until measured
Moderate (4 points)
Symptom: weak airflow at the registers
MERV 11, not higher, until measured
Elevated (6 points)
Symptom: whistling at the return
MERV 11, not higher, until measured
Elevated (6 points)
Symptom: the filter is visibly bowed
MERV 6 — below the MERV 8 fitted now
High (7 points)
Symptom: ice on the coil
MERV 6 — below the MERV 8 fitted now
High (8 points)
Symptom: the furnace trips its limit
MERV 6 — below the MERV 8 fitted now
High (8 points)
HyreHVAC calculation: every figure is the engine’s own output, run on September 5, 2026 with one input changed at a time.
Look at the pattern. A media cabinet lowers the risk two steps. Shrinking the face from 20×25 to 14×14 raises it two steps. Any hard symptom stops everything, however good the rest looks.
Questions this calculator answers
What MERV rating do I need?
MERV 13 if your system can carry it. EPA recommends "at least a MERV 13 rating, or as high a rating as your system fan and filter slot can accommodate". People drop the second half, and it decides whether MERV 13 helps or strains your equipment. Screen it above, then have static pressure measured.
Is a higher MERV filter always better?
No. A tighter filter cuts airflow. Low airflow over a cooling coil reduces cooling and can freeze it, and over a furnace heat exchanger it trips the high-limit switch. EPA says existing systems "may not have enough fan or motor capacity" for higher-resistance filters.
What does MERV actually measure?
How well a filter catches particles in three size ranges, per ASHRAE Standard 52.2. MERV 1 through 10 have no requirement for particles under one micrometer. MERV 11 is the first rung that asks, at 20%; MERV 13 asks for 50%.
How much pressure drop does a MERV 13 filter add?
No single number is honest. In a ten-home field study, filters rated MERV 4 to 13 measured 16 to 173 Pa, a tenfold spread. Depth, face area, pleats, media and airflow matter more than the rating. A per-MERV figure is an average of other houses.
Will a MERV 13 filter damage my furnace?
Only if the system has no pressure headroom. In the field study, one home’s filter pressure did not change with MERV 16, while another rose tenfold. Be careful with a 1-inch 14×14 slot on a fixed-speed blower with a cooling coil.
Is a 4-inch filter better than a 1-inch?
Yes, for airflow. EPA says deeper pleated filters limit resistance, and the field study found 4-inch MERV 16 filters less restrictive than 1-inch ones. It usually means fitting a media cabinet at the air handler, which is what makes a high MERV safe.
My filter is sucked in and bowed. What does that mean?
The pressure across it is high enough to bend it. Air also starts slipping around the frame, so you lose filtering and airflow together. Fit the least restrictive filter the slot takes and have static pressure measured. Do not tape or pack the track.
What should I ask an HVAC contractor about filters?
Three numbers, in writing, in inches of water column: total external static pressure across the air handler, the pressure drop across the filter alone, and the maximum static pressure in your equipment’s manual. Without them, "your system can’t handle MERV 13" cannot be checked.
How do MPR and FPR convert to MERV?
They do not. MPR and FPR are makers’ own rating scales, which EPA lists as separate from MERV. There is no published conversion, so if that is all your box shows, treat the MERV as unknown.
Should I run the fan all the time to filter more?
It does filter more, since a central system filters nothing when idle. It also uses power all day, and on a system already short of airflow it adds hours under strain. Settle the filter question first, then the fan question.
Does this tool recommend a filter brand?
No. HyreHVAC sells no filters, services no equipment and takes no commission. You get a MERV ceiling and a question to ask.
What is a MERV rating? (US Environmental Protection Agency, Indoor Air Quality, retrieved 2026-09-05. EPA’s conditional MERV 13 recommendation, the starting point of this screen.)
Energy Implications of In-Line Filtration in California Homes (CEC-500-2013-081) (Walker, Faulkner, Dickerhoff and Turner, Lawrence Berkeley National Laboratory, for the California Energy Commission, retrieved 2026-09-05. Ten homes, each monitored a year or more. Every measured pressure drop and airflow loss on this page. Retrieved through OSTI; the CEC copy returned 404.)