The higher the MERV value is the value the more efficient the filter will be in trapping airborne particles. Another consideration is air flow through the your HVAC system. Leaving a dirty air filter in place or using a filter that is too restrictive may result in low air flow and possibly cause the system to malfunction. The filter will trap Average Particle Size Efficiency. Types of things these filters will trap. MERV 1. Pollen, dust mites, standing dust, spray paint dust, carpet fibers.
MERV 2. MERV 3. MERV 4. MERV 5. The MERV rating of a furnace filter represents its ability to filter out air contaminants—a filter with a lower MERV rating would be able to trap fewer particles and contaminants in comparison to one with a higher rating. When trying to determine the right MERV rating for your air filter, however, it is vital to bear in mind that the MERV rating of a furnace filter denotes its minimum capacity.
These two ratings differ greatly when it comes to filtration capacity. The air handler or blower in every furnace can take a specific amount of pressure drop.
Since filters with a high MERV rating offer high resistance to the airflow, their pressure drop is also greater. However, if your furnace is older or sensitive to airflow, it may not be able to handle a filter with a higher rating. Switching from one of these ratings to the other makes a world of difference in terms of performance. Whichever MERV rating you end up choosing, it is imperative that you replace your filter periodically to keep your furnace in top shape for years to come.
Your browser is out-of-date! MERV 11 vs. The MERV 11 rating is one of the most popular choices when it comes to residential use. The MERV 13 is less popular and is the highest rating that is recommended for residential use. A MERV 11 rated furnace filter can trap the majority of harmful contaminants that are present in the air. This includes pollen, dust, lint, mold, dust mites, smoke, pet dander, and smog.
Again, see article for why this is a better idea than microfiltration. More surface area means more air flow. Flattening the filter media does not change what it stops and lets through. You asked if it would help to protect against Coronavirus exposure.
It will help, yes. But you will still need goggles for eye protection and still practice social distancing. Also, were I myself to try this MERV13 filter modification, I would make many filter disks and change them after every exposure to several people. They cannot be recycled, so be prepared to make hundreds of them. Whatevr contraption you make, be sure that the edges of the filter are making a good seal around you face.
No beards! Best of luck. While this assumption may have carried some clout a decade or so ago when these high-efficiency filters were new, modern varieties can actually increase airflow, save you money, and keep your system cleaner. The higher the MERV, the more particulates filters collect. However, high-MERV filters offer superior filtration, trapping everything from construction dust and tobacco smoke to bacteria. By installing an air filter with a high MERV rating, two things happen.
First and foremost, your air becomes cleaner, which can help improve the longevity of your HVAC system. The more particulates that are trapped, the fewer get stuck to the interior of your vent work, and the better the airflow becomes.
Additionally, high-MERV air filters that contain pleats create a lot more surface area for air to blow over, which can improve airflow and reduce the strain on your system. A big drop across the filter means the pressure in the return duct is lower, not higher. But the pressure difference between the return duct and the air outside it will be higher as a result. Also, the total external static pressure in the system will increase.
I just realized we have two I just realized we have two different pictures in our head. Not all of us know what a Not all of us know what a Michigan Basement is. As I recall it is not a basement in Michigan. I actually did just mean a I actually did just mean a basement in Michigan in this case, to differentiate from an attic in Georgia.
But for the record what we call a Michigan Basement, which is probably not unique to here, is when a crawlspace is dug out into a basement and the soil under the existing footing is shored up sometimes in frighteningly inadequate ways. They are easily recognized by the step in the wall and low ceiling height I think people got tired of digging.
Good question, Lee. It could be in a standalone filtration system with its own fan. It could be part of the ventilation system.
One option, particularly for One option, particularly for the South, is a Ventilating Dehumidifier e. Comes with a MERV 13 filter. James, yes, a ventilating dehumidifier is a good choice for mixed-humid and hot-humid climates and it can definitely help with the filtration. Depending on the size of the house and the static pressure, though, you may or may not get enough filtration volume.
Also has my favorite controls in the Broan line because you can independently select the high and low speeds, each from the full range, and balances by reducing motor speed instead of dampers. Hi Allison. I just want to Hi Allison. Having filtration powers independent from heating and cooling demand is a good thing anyway.
Avery, you are correct. Ductless mini-split heat pumps come with a little filter whose job is to keep the coil clean. You have to clean it regularly to keep the air flow up. Thanks Allison! This is a Thanks Allison! This is a really big deal. And without skilled professionals knowledgeable of proper filtration and its appropriate motor sizing you can be creating problems instead of solving them.
All too true, Charles. This is why a deep filter This is why a deep filter media cabinet and a semi-annual preventive maintenance program comes with every heat pump system we install. Proceed with caution. Great topic and discussion. It was from but still quite relevant I think. Here is a link to the free article:. And yes, it is absolutely still relevant. No particles would get through it, but no air would get through it either. I was fairly comfortable I was fairly comfortable looking at filtration for PM2.
Ozone causing new chemical combinations? Great article. Improper Great article. In new construction this is easy to achieve. My specs require filter face velocity not to exceed FPM, or roughly 2 sq. Problem solved. Existing construction is more challenging. Simply replacing a 1 inch filter with a 4 inch may not be enough, especially if the filter cabinet is mounted at immediately before the blower sized to match the return opening.
Otherwise bypass will eat your lunch. That research is for ambient outdoor air or specialized research or manufacturing environments. Unless you have a local ozone source, there is seldom enough ozone indoors to cause those issues. A metallic coil is an excellent ozone filter, so nearly all residential HVAC systems are effective ozone filters.
And residential HVAC system design is the wrong place to address ultrafine particles or filtering to clean room standards. And in much of the mid-Atlantic — without forced-air HVAC units maybe add-on AC units with air handlers and ducts run in all the wrong places. But D. Love this comment. We like Love this comment. And that applies to flirtation. It is really sad that most It is really sad that most manufacturers do not report air pressure drop clean or dirty.
The general thinking is that the higher the filter efficiency, the higher the pressure drop, but that is not always true. That puzzled us at first until we noticed that the highest efficiency filter had many more pleats, thus more surface area.
Unfortunately, without any published information on this, the buyer cannot make an informed decision. No one is filtering exterior air for us. The purpose of a furnace filter is to protect its equipment. Using a filter designed to just do that does not put system function at risk if the filter is regularly maintained. The way HERS rating is done The way HERS rating is done in California has for some time militated towards outdoor air supply being provided by a separate route from heating and cooling, as an uncontrolled CFI outdoor air intake is not allowed to be sealed off during duct leakage verification.
Also, most low-capacity air handlers are not capable of mounting the static pressure needed for high-MERV filters, so CFI setups with those often necessitate inline booster fans. Moreover, while I try to educate my clients on the merits or lack thereof of expensive, restrictive high-MERV filters, who am I to dictate what type of filter they want to use. Cudos to Allison for calling attention to this issue in this blog. Actually, I have one thing to Actually, I have one thing to bounce off the forum.
However, I never see much of anything in the electrified stage. Addressing a problem is a job, treating its symptoms is a career. Where that eventually takes us should be self evident. I follow that up with explaining how there are several devices and appliances designed to clean homes including vacuum cleaners, but that HVAC systems are not one of them. Individuals differ in their Individuals differ in their need for high cleanliness air. Those who suffer from idiopathic pulminary fibrosis may reasonable hope that higher quality air filtration will help prolong their life, already shortened by the disease.
Your article is very confusing. Sorry for any confusion, Dan. MERV 16 is the highest on the scale but those are hard to find. Mcmaster Carr makes the Merv Mcmaster Carr makes the Merv air bags which are being tested for face masks by some universities.
If by chance, the EPA source is incorrect, or if you think I have misinterpreted it, I welcome a conversation. Thanks much. The extra pleats make the The extra pleats make the area the air flows over larger so your HVAC will not work any harder. A simple test with an amp meter confirms this. I might point out here that most viruses are even smaller than. Aside from crowded indoor Aside from crowded indoor spaces, the risk from aerosolized viruses is very small — the real risk comes from virus-containing droplets, which are much larger.
N95s are very good at stopping those. I placed mask and filter in the oven at Fahrenheit for 5 min. All plastic and rubber components held up well. My question is, does this degrade the filter in any way?
If I can find them, I will post, as there are lots of individuals adding their expertise. Ryerson University — in Toronto, Ontario, Canada may have something or someone to contact too. Good Luck! This is a very easy mask to This is a very easy mask to make and no ear problems.
Use 4 masks, numbered on the outside , for each day. They can be used each day in numbered sequence. Then start sequence over starting with mask number 1. All viruses on the mask will be dead in days. I use this method and use paper lunch bags to store each mask and number the bags and replace each bag after using each mask. First, I love your sense of First, I love your sense of humor.
I have exactly the same concerns as you do…. I want to introduce a carbon I want to introduce a carbon filter, the only problem is the carbon filter is a Merv 8. If I add a second filter merv 13 is that a good idea? Never cascade filters because Never cascade filters because the accumulative restriction on the system will be too great.
A MERV 8 carbon filter will provide more than enough dust and allergen filtering and it will filter out dozens of toxic gasses that will pass right thru a MERV 13 filter. Thank you. If you want to use pleated filters and higher MERV filters the only safe way to do so is have a inch media filter installed by a professional.
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