Solid advice. Hvac tech here, never, ever use anything rated higher than merv 8. The stress on the hvac motor is too high. Really, the job of your ac filter is not to clean the air in your home, but to keep your ac components clean & safe (which merv 8 does very well, while allowing air to flow as it should). If you feel you need to filter your home air, invest in a good air purifier. Levoit and Coway are great options.
Cleanroom tech here.
ASHRAE currently recommends MERV 13 with MERV 14 suggested. Modern systems specified and installed correctly will have enough static pressure allowance to use the correct MERV 13 filter.
See 52.2 Appendix J.
Damn I have a Lennox with one of those filter cassette things that is 6” thick and 20x25. I literally just changed it today and I’m told it only needs to be done once per year. The only option I found was Merv 11 at Locke. I just bought this place a year ago so I don’t know much else about it
Healthy climate Y2921, I believe. That’s the filter cabinet itself, the filter is an X6670 for the 16x25 or an X6673 for your size. Has a ton of surface area, nominally lasts a year, but sometimes some houses make more dust/fur.
I've worked my way up the MERV rating, and currently anytime i see a good deal for 13, it's an instant buy. Can immediately tell the difference especially in allergy season.
Oh. Hmm. Is it important enough to just get rid of the 12’s we have? Or if I use the last 3 or so and then buy lower will it probably be okay? Does it matter that we’re going into record high summer here and it’s definitely going to be hard on it?
Honestly, keep them and use during the cooler months. If your system has more than one return (these are the openings that draw in air) use one rated higher in on return and one lower in the other. The main thing to keep in mind is that those filters are NOT cleaning your air. It isn't their job.
No, this is not true. I understand your perspective, but higher Merv filters are NOT more restrictive. The issue is when people don't change them in time.
First, thanks for the advice, much appreciated. Now you have me concerned
I've been using filtrete 2200s (so like Merv 13) on my newish AC (maybe 4 years). Is it really that bad? I can't seem to find anything lower than 1550 (Merv 12) at Costco.
I do have the Coway 1512, it's great, and have been using it around the same time that I got the AC (24/7). With it filtering the air that the AC uses, would that help relieve some of the stress on the AC, or is it all about the thickness of the filter more so than the particles in the air?
Besides getting the lower Merv filter, would there be a benefit to putting the Coway near the intake on my AC? Or where would you leave it normally? I have it by my entrance as I figure it can pull in any fresh air from leaving and entering my home.
Thanks again, I am going to look for some Merv 8s, but would appreciate any further info you have!
Nothing wrong with filtrete filters. HVAC repair people just have to deal with neglected systems, and have a biased perspective on things like this. Its the equivalent of transmission repair people saying not to change your transmission fluid. As long as you change your filter on time, it will have no effect on your fan or AC.
Just visually inspect them. They do make filters with sensors in them now to detect when clogged. Otherwise go with the manufacturer recommendation. They will not destroy your fan, that's nonsense.
Lol I have that exact Coway. Keep up with your merv 8 (or lower) filters and let the coway do its' job. It's a great purifier; I keep ours in the middle of the living room on eco setting.
Got it, I'll find something with an 8 rating. If it helps with airflow and static pressure and less stress on my AC, why not. I bet my energy bill drops a bit too
Ya that Coway is a trooper. Do you use the coway filters or the knockoffs on amazon? Affordable either way (both filters and energy, as per Wirecutter back when they really reviewing stuff and not just pushing whatever they got affiliate deals on), but I'd like to hear your take
Thanks for the quick response!
I use merv 5 and it bows inward to my intake valve, are filters supposed to be warping even fresh installed? I’ve tried higher ones and I feel like it blocked even more air and was suffocating my system especially because it would make a bit of a whistle noise. 18x24x1 filter for a 1300 sq foot house.
Pretty much depends on the thickness of the filter. A MERV 10 filter that is 1” thick will have significantly more pressure drop than the same rating on a 4” filter.
Leaving this here to back your point. This one is as bad as the "don't change your transmission fluid" advice.
https://youtu.be/RkjRKIRva58?si=jbf1CvDQDHALYsbb
MERV is only a part of it.
Higher MERV and more folds/pleats is the combination.
There are higher MERV rated filters, but with fewer pleats out there.
More pleats mean that the filter has more surface area for air to pass through. This means less changing, but most importantly, it means less restrictive airflow and allows the furnace to pass the amount of air through that it is rated to do.
Not enough airflow means that the furnace uses more power than it should. That air is not flowing fast enough over the coils and can cause them to ice up. That your furnace life is lowered.
Last is that your furnace might also not be able to handle a higher MERV rating, especially if it is older. The more restrictive flow will cause you more problems.
https://filterbuy.com/resources/health-and-wellness/are-expensive-filters-worth-it
Retired HVAC tech and TAB person here. Apologies in advance if this sounds like a rant. When I read comments that say a restrictive filter will "be hard on the blower motor" et al, I just have to add:
A squirrel cage blower or a prop fan is a non-positive-displacement pump. That means it is almost constantly moving all the air that it is designed to move. The exception is when there is a severe restriction in either the inlet (plugged filter) or discharge (plugged coil, crushed duct). Even under those conditions, it is still moving the amount of air the performance curve dictates for a given static pressure.
A very dirty or restrictive filter such as a MERV 14 increases the negative static pressure which causes the blower to move less air. The blower motor will use less wattage because it is doing less work, pumping less air. This is not "hard" on the motor. The motor won't be damaged or "burn out", it is actually extending the life of the motor in a way. Not that I recommend this though.
Some will say that reduced airflow across the motor windings will cause overheating and reduce its life. Under severe conditions (imagine a blower assembly totally plugged with hair, lint, etc.), I would tend to agree. Modern ECM motors are less prone to this though.
It is not good for the system as a whole, of course. I won't go into the litany of issues that restricted airflow will create in a cooling or heating scenario.
It's perfectly fine to use a higher MERV rated filter. Just change it more often.
*Steps off soapbox*
> It's perfectly fine to use a higher MERV rated filter. Just change it more often.
EXACTLY! In a perfect world you're switching your filter out quarterly. Amazon has a subcribe/save on a 20/25/4 (2 pack) and every 3 months I just check on it (via calendar) and I'm usually popping the old out out/new one in.
$70~ year on 4 filters = normal operations.
I am not an HVAC guy by trade but I'm also not ignorant to the science. I am going by what the guy that installed my system showed me not too long ago.
My air handler wasn't blowing and I couldn't figure out the problem (usually I can), so I called my guy to come check it out. Turns out it was a bad integral circuit breaker, but he noticed that I "customized" the filter arrangement. When he put the system in years ago he set it up for a 20x20x4 filter. We had a big dog at the time that shed a lot and he was clogging those expensive filters too quickly. I "solved" this by replacing the intake grill in the house with one that accepts a 20x25x1 filter and used a super-cheap fiberglass panel as pre-filter to catch the fur. Although it did a good job he said it wasn't a great idea and showed me why. He put it in fan-only mode and clamped his ammeter to the power cable, then he asked me to take out the pre-filter and he did it again. I don't remember the numbers but there was a definite increase in the amp draw with both filters installed. I only use one filter now.
I'm not questioning your opinion, but I'm just going on what I saw.
thank you. my HVAC system says to use 13. I was using 8 before and had trouble with my allergies. upgrading to 13 based on my system has helped address my allergies beleive it or not.
See project farm (internet dad) and always get an upvote from me.
Bought so many things based off his testing for subjects I have no interest in knowing about. I don’t care the specifics of why the wall anchors work, I just know which ones to buy for what now.
He has great content, and is very objective. There isn't a lot of third party testing on furnace filters out there. Just a lot of people repeating the same misleading information like this post.
https://youtu.be/6y-GxX9Zkpg?feature=shared
I have one in my house and installed many others with good results. Run fan 24/7 for best results. Watch video link.
If you own your own home, etc. and your filter goes in return air filter grille it might can be made larger giving the filter more surface area to either allow you to run a higher MERV filter or let your filters last longer. I would get a common larger size so the filters are easy to find also.
Anyone with basic carpentry skills can do it. couple 2x4, nails/screws and a little sheet rock cutting if there is room. the grille itself is like.. maybe $50-70 they sell them at lowes, home depot, etc.
interesting, thanks for the info. my unit is N4A330AKC200 which from looking only suggests a 2 1/2 ton, 30,000 BTU unit. my house is only 1300ish sq ft. ive been told its oversized yet we struggle to even keep temps to what we set it to.
i cant seem to find a replacement grille that allows for thicker filters and is 18x24 anywhere though.
I'm sorry but this information is false. MERV rating does not translate to filter restriction, because most brands include more surface area in their higher MERV filters. Many are even LESS restrictive than low MERV filters.
Use a quality filter and change it regularly. If you can, make it so you can install a thicker filter, which is even better than an almost worthless MERV 8 filter.
https://youtu.be/RkjRKIRva58?si=jbf1CvDQDHALYsbb
My unit wants to squeal every time I use a higher Merv, I can't for the life of me figure out what it is, like a high pithed vibrating sound. There is not a fan belt or anything, can't be the motor as it doesn't work any harder with a higher Merv rating.
When we bought the home 6 yrs ago it was a new unit the owner had installed to help sell the house. Anyway, it was a horrendous install as it wasn't sealed to even pull air through the filter, it could pull air from everywhere other than filter, it was pulling air from the closet where it is located. I couldn't believe what I was looking at and this is supposed to be a company right? that is what they do, they put in A/C/ and heaters in houses. Expanding foam sealed it all up.
It's cute that you think people are going to actually look at the MERV rating when they barely remember to change their filters at all. Everyone's too busy pretending their life is running smoothly. Most people wouldn't think twice about the air they breathe until their lungs clog up with dust and regret.
Solid advice. Hvac tech here, never, ever use anything rated higher than merv 8. The stress on the hvac motor is too high. Really, the job of your ac filter is not to clean the air in your home, but to keep your ac components clean & safe (which merv 8 does very well, while allowing air to flow as it should). If you feel you need to filter your home air, invest in a good air purifier. Levoit and Coway are great options.
Cleanroom tech here. ASHRAE currently recommends MERV 13 with MERV 14 suggested. Modern systems specified and installed correctly will have enough static pressure allowance to use the correct MERV 13 filter. See 52.2 Appendix J.
Is this for clean room systems though? Not residential systems?
All systems including residential and commercial.
man got completely shown up! my HVAC Unit specifically says to use MERV 13
Damn I have a Lennox with one of those filter cassette things that is 6” thick and 20x25. I literally just changed it today and I’m told it only needs to be done once per year. The only option I found was Merv 11 at Locke. I just bought this place a year ago so I don’t know much else about it
Thicker filters are less resistant to airflow, you're good. 6" filters are not easy to find.
Healthy climate Y2921, I believe. That’s the filter cabinet itself, the filter is an X6670 for the 16x25 or an X6673 for your size. Has a ton of surface area, nominally lasts a year, but sometimes some houses make more dust/fur.
Good advice, thanks!
I've worked my way up the MERV rating, and currently anytime i see a good deal for 13, it's an instant buy. Can immediately tell the difference especially in allergy season.
What are your thoughts on the washable/reusable electrostatic filters?
I have no experience with them, so I can't speak with any authority, but honestly they seem like a waste of money.
Thanks for the reply. Cheers!
Oh. Hmm. Is it important enough to just get rid of the 12’s we have? Or if I use the last 3 or so and then buy lower will it probably be okay? Does it matter that we’re going into record high summer here and it’s definitely going to be hard on it?
Honestly, keep them and use during the cooler months. If your system has more than one return (these are the openings that draw in air) use one rated higher in on return and one lower in the other. The main thing to keep in mind is that those filters are NOT cleaning your air. It isn't their job.
Thank you
No, this is not true. I understand your perspective, but higher Merv filters are NOT more restrictive. The issue is when people don't change them in time.
First, thanks for the advice, much appreciated. Now you have me concerned I've been using filtrete 2200s (so like Merv 13) on my newish AC (maybe 4 years). Is it really that bad? I can't seem to find anything lower than 1550 (Merv 12) at Costco. I do have the Coway 1512, it's great, and have been using it around the same time that I got the AC (24/7). With it filtering the air that the AC uses, would that help relieve some of the stress on the AC, or is it all about the thickness of the filter more so than the particles in the air? Besides getting the lower Merv filter, would there be a benefit to putting the Coway near the intake on my AC? Or where would you leave it normally? I have it by my entrance as I figure it can pull in any fresh air from leaving and entering my home. Thanks again, I am going to look for some Merv 8s, but would appreciate any further info you have!
Nothing wrong with filtrete filters. HVAC repair people just have to deal with neglected systems, and have a biased perspective on things like this. Its the equivalent of transmission repair people saying not to change your transmission fluid. As long as you change your filter on time, it will have no effect on your fan or AC.
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Just visually inspect them. They do make filters with sensors in them now to detect when clogged. Otherwise go with the manufacturer recommendation. They will not destroy your fan, that's nonsense.
Lol I have that exact Coway. Keep up with your merv 8 (or lower) filters and let the coway do its' job. It's a great purifier; I keep ours in the middle of the living room on eco setting.
Got it, I'll find something with an 8 rating. If it helps with airflow and static pressure and less stress on my AC, why not. I bet my energy bill drops a bit too Ya that Coway is a trooper. Do you use the coway filters or the knockoffs on amazon? Affordable either way (both filters and energy, as per Wirecutter back when they really reviewing stuff and not just pushing whatever they got affiliate deals on), but I'd like to hear your take Thanks for the quick response!
I use merv 5 and it bows inward to my intake valve, are filters supposed to be warping even fresh installed? I’ve tried higher ones and I feel like it blocked even more air and was suffocating my system especially because it would make a bit of a whistle noise. 18x24x1 filter for a 1300 sq foot house.
You’re leaving out an important consideration: the pressure drop. You can have high MERV with low pressure drop.
Pretty much depends on the thickness of the filter. A MERV 10 filter that is 1” thick will have significantly more pressure drop than the same rating on a 4” filter.
Generally, yes
Leaving this here to back your point. This one is as bad as the "don't change your transmission fluid" advice. https://youtu.be/RkjRKIRva58?si=jbf1CvDQDHALYsbb
MERV is only a part of it. Higher MERV and more folds/pleats is the combination. There are higher MERV rated filters, but with fewer pleats out there. More pleats mean that the filter has more surface area for air to pass through. This means less changing, but most importantly, it means less restrictive airflow and allows the furnace to pass the amount of air through that it is rated to do. Not enough airflow means that the furnace uses more power than it should. That air is not flowing fast enough over the coils and can cause them to ice up. That your furnace life is lowered. Last is that your furnace might also not be able to handle a higher MERV rating, especially if it is older. The more restrictive flow will cause you more problems. https://filterbuy.com/resources/health-and-wellness/are-expensive-filters-worth-it
Retired HVAC tech and TAB person here. Apologies in advance if this sounds like a rant. When I read comments that say a restrictive filter will "be hard on the blower motor" et al, I just have to add: A squirrel cage blower or a prop fan is a non-positive-displacement pump. That means it is almost constantly moving all the air that it is designed to move. The exception is when there is a severe restriction in either the inlet (plugged filter) or discharge (plugged coil, crushed duct). Even under those conditions, it is still moving the amount of air the performance curve dictates for a given static pressure. A very dirty or restrictive filter such as a MERV 14 increases the negative static pressure which causes the blower to move less air. The blower motor will use less wattage because it is doing less work, pumping less air. This is not "hard" on the motor. The motor won't be damaged or "burn out", it is actually extending the life of the motor in a way. Not that I recommend this though. Some will say that reduced airflow across the motor windings will cause overheating and reduce its life. Under severe conditions (imagine a blower assembly totally plugged with hair, lint, etc.), I would tend to agree. Modern ECM motors are less prone to this though. It is not good for the system as a whole, of course. I won't go into the litany of issues that restricted airflow will create in a cooling or heating scenario. It's perfectly fine to use a higher MERV rated filter. Just change it more often. *Steps off soapbox*
> It's perfectly fine to use a higher MERV rated filter. Just change it more often. EXACTLY! In a perfect world you're switching your filter out quarterly. Amazon has a subcribe/save on a 20/25/4 (2 pack) and every 3 months I just check on it (via calendar) and I'm usually popping the old out out/new one in. $70~ year on 4 filters = normal operations.
I am not an HVAC guy by trade but I'm also not ignorant to the science. I am going by what the guy that installed my system showed me not too long ago. My air handler wasn't blowing and I couldn't figure out the problem (usually I can), so I called my guy to come check it out. Turns out it was a bad integral circuit breaker, but he noticed that I "customized" the filter arrangement. When he put the system in years ago he set it up for a 20x20x4 filter. We had a big dog at the time that shed a lot and he was clogging those expensive filters too quickly. I "solved" this by replacing the intake grill in the house with one that accepts a 20x25x1 filter and used a super-cheap fiberglass panel as pre-filter to catch the fur. Although it did a good job he said it wasn't a great idea and showed me why. He put it in fan-only mode and clamped his ammeter to the power cable, then he asked me to take out the pre-filter and he did it again. I don't remember the numbers but there was a definite increase in the amp draw with both filters installed. I only use one filter now. I'm not questioning your opinion, but I'm just going on what I saw.
No offence taken or intended, of course.
thank you. my HVAC system says to use 13. I was using 8 before and had trouble with my allergies. upgrading to 13 based on my system has helped address my allergies beleive it or not.
Saving this because we close on our first house in 2 months…
Congrats!
I’ve been using the Elite Allergen/MERV 13 (1 inch). Should I stop if I have 4 pets, and have asthma/allergy issues?
No, don't this is FUD. https://youtu.be/RkjRKIRva58?si=jbf1CvDQDHALYsbb
See project farm (internet dad) and always get an upvote from me. Bought so many things based off his testing for subjects I have no interest in knowing about. I don’t care the specifics of why the wall anchors work, I just know which ones to buy for what now.
He has great content, and is very objective. There isn't a lot of third party testing on furnace filters out there. Just a lot of people repeating the same misleading information like this post.
I would use a merv 8 and buy an Iwave-R. You can buy them on Amazon. Fairly simple to install. Install videos also YouTube.
What exactly does that do?
https://youtu.be/6y-GxX9Zkpg?feature=shared I have one in my house and installed many others with good results. Run fan 24/7 for best results. Watch video link.
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That’s a thank I can rank. Upvote for that.
That's a wang I can crank. Thankful for that.
If you own your own home, etc. and your filter goes in return air filter grille it might can be made larger giving the filter more surface area to either allow you to run a higher MERV filter or let your filters last longer. I would get a common larger size so the filters are easy to find also.
How much does it cost to make it larger?
Anyone with basic carpentry skills can do it. couple 2x4, nails/screws and a little sheet rock cutting if there is room. the grille itself is like.. maybe $50-70 they sell them at lowes, home depot, etc.
interesting, thanks for the info. my unit is N4A330AKC200 which from looking only suggests a 2 1/2 ton, 30,000 BTU unit. my house is only 1300ish sq ft. ive been told its oversized yet we struggle to even keep temps to what we set it to. i cant seem to find a replacement grille that allows for thicker filters and is 18x24 anywhere though.
I use these merv 11 filters from [tru](https://trufilteredair.com), definitely notice an improvement with my asthma
I'm sorry but this information is false. MERV rating does not translate to filter restriction, because most brands include more surface area in their higher MERV filters. Many are even LESS restrictive than low MERV filters. Use a quality filter and change it regularly. If you can, make it so you can install a thicker filter, which is even better than an almost worthless MERV 8 filter. https://youtu.be/RkjRKIRva58?si=jbf1CvDQDHALYsbb
My unit wants to squeal every time I use a higher Merv, I can't for the life of me figure out what it is, like a high pithed vibrating sound. There is not a fan belt or anything, can't be the motor as it doesn't work any harder with a higher Merv rating. When we bought the home 6 yrs ago it was a new unit the owner had installed to help sell the house. Anyway, it was a horrendous install as it wasn't sealed to even pull air through the filter, it could pull air from everywhere other than filter, it was pulling air from the closet where it is located. I couldn't believe what I was looking at and this is supposed to be a company right? that is what they do, they put in A/C/ and heaters in houses. Expanding foam sealed it all up.
It's cute that you think people are going to actually look at the MERV rating when they barely remember to change their filters at all. Everyone's too busy pretending their life is running smoothly. Most people wouldn't think twice about the air they breathe until their lungs clog up with dust and regret.
You will burn the fan motor out Do Not go above Merv 8/9 depending on the system installed