Choosing The Right AC Filter

Ask 3 HVAC service technicians what kind of AC filter you should use, you’ll probably get three different answers.

The Rock Stopper AC Filter

disposable air filter Technician 1: “Just get the cheapest disposable AC filter and change it every 30 days.”

Technician 1’s opinion is based on the premise that a cheap filter will restrict airflow the least. Therefore, it will be easier on the unit and components won’t ‘work as hard’. His opinion isn’t 100% wrong, although it’s not 100% right either.

PRO TIP: In the air conditioning business, we jokingly refer to the cheap disposable AC filters as “rock stoppers”. Reason being, anything larger than a rock is going right through that AC filter like water through a spaghetti strainer!


The Pleated Air Filter

which ac filter to buyTechnician 2: “I recommend a good 90-day pleated filter like the ones made by 3M.” Technician 2’s line of thinking is more about improving the homes air quality and what you’re breathing into your lungs. He/she may have children with allergies or asthma and the health benefits of a better AC filter outweigh airflow restriction. He or she is also probably considering sacrificing ‘some’ air quality as opposed to costlier AC filtration systems.

Like the first technician, Technician 2’s opinion isn’t necessarily wrong, but it isn’t necessarily right either.


The HEPA Filtration System with Air Purifier

merv 16 and air purifierTechnician 3: “I recommend the best HEPA (hospital grade) whole home filtration system with both filtration and air purification.” Technician 3 probably even knows the stats, like the fact that “it will remove 99.9% of contaminants from the air.” He’ll get into “particulates” down to this “micron” size and all kinds of other nerdy info!

Like the two technicians before him, Technician 3’s opinion has validity. Some people will love how much he knows about it and take his advice. Yet others, will think Technician 3 just wants to sell expensive products and laugh all the way to the bank. However, Technician 3, like the two before him isn’t necessarily right or wrong either. While he may know more about air quality than the others, he still gave his ‘opinion’ without all the facts.


So, who’s right? Which AC Filter Should You Use?

Like I said, technically none of them are right and none of them are wrong. Here’s why:

All three technicians answered the question above based on their opinion of what was important to them. None asked about what was most important to you.

air conditioning filters to useNone asked:

  • Does someone in the home have allergies, asthma, lung disease or other health issues?
  • Are you a do-it-yourselfer, or do you want your service company to handle everything for you?
  • How much do you spend on AC filters and how often do you change them now?
  • What’s your budget if considering a filtration ‘system’?
  • How often are you having to dust your home?

In other words, as a technician, we really need more information from you and what your needs & priorities are. Only then, can a technician advise on what kind of filter you should use!


Choosing the Right Air Filter for the Equipment

PRO TIP: Before choosing the which AC filter you should use; we need to determine your ductwork static pressure.

ductwork analogyI like to use the milkshake/straw analogy when explaining static pressure. When you try to suck a milkshake through a regular straw it takes a lot of work to get to the goodness. However, when they give you one of those fat milkshake straws, it’s pretty much instant gratification! The static pressure is much higher in the skinnier straw than it is in the fatter straw.

High static pressure in a duct system makes your air conditioning & heating system work harder. Frankly, high static pressure problems should be fixed even if you’re not considering which AC filter you should use. Reducing the static pressure in your ductwork not only improves airflow, but it also prevents breakdowns, and your equipment will last longer.


Technician 1 – The Rock Stopper

this will doTechnician 1 assumed your system couldn’t handle better filtration. Or should’ve proposed what it would take to fix the duct issues so you could have better filtration.

If your ductwork has high static pressure you shouldn’t restrict it any further by using a better filter. In fact, better filtration will make your static pressure even higher. However, using a rock-stopper is not the answer – correcting the airflow issues is the right answer.

The very point of filtration is to clean the air you and your family are breathing every day. So, why just throw your hands up and say, “oh well, I’m just going to have to live these problems”. My family and I will just live with asthma attacks, frequent colds, influenza, etc.

Again, while Technician 1’s opinion wasn’t necessarily wrong, he didn’t take everything into consideration. He was focused strictly on the equipment and not your health or the concept of fixing the ductwork issues.


Technician 2 – The “Better” Solution

this is an improvementWe’re all keenly aware of the importance of good filtration and decreasing the spread of germs thanks to the pandemic. However, there’s a lot of other nasty contaminants in the air we breathe that impact our daily & long-term health.

For example: The AZ Dept. of Health reported a 35% increase in people diagnosed with Valley Fever in recent years. Valley Fever is a disease caused by airborne germs and fungi carried in the dust.

Did you know the air in your home is likely 300 times more polluted than the air outside? I bet these are some of the things that Technician 2 was thinking about when he gave his opinion to go with a “better” filter.

PRO TIP: Disposable fiberglass filters are considered “good” (which is using the term word good rather loosely). Pleated filters are considered “better”. HEPA filters and certain Electronic Air Cleaners are considered the “best” filtration.

Technician 2 probably considered the fact that the “better” AC filter would raise the ductwork static pressure. He likely believed the health benefit was worth the sacrifice. Again, his ‘opinion’ was not necessarily wrong, but was only based on what matched his belief system and values.


Technician 3 – Air as Clean as a Hospital’s Surgery Room

the bees kneesFor the record, I personally use Technician 3’s recommended filtration and purification system in my own home. That said, I have an interstitial lung disease and my wife suffers from allergies – clean air is a top priority for us. In other words, the best possible indoor air quality solution is more important to us than the price tag.

I also own two of the priciest air conditioning & heating systems on the market (Lennox XC25’s). So, while I may be an HVAC contractor, I’m not a billionaire and don’t want to strain my equipment. I made sure my ductwork static pressure was within manufacturer specs before & after installing my filtration systems.

I tend to agree with Technician 3’s opinion of what kind of AC filter you should use. However, that’s based on what’s important to me and the benefits and results outweigh the costs – for me. So, while it’s hard to imagine anyone not caring about the air they’re breathing – perhaps it’s not their top priority. For that reason, even Technician 3’s opinion may not be the right answer for you.


Summary – Which AC Filter Should You Buy?

First, answer the questions I posed above that the 3 technicians failed to. Next, think about your budget and how much you are willing to spend to achieve the results you wish. Very clean air is not a pipe dream, the technology exists, and it works extremely well.

I can tell you from personal experience, I rarely get colds, the flu, or have the respiratory issues I once did prior to using good IAQ equipment at home. I’m a believer, not only because I know the product and the numbers, but I’m also a literal user of these products.

That said, rock stoppers (“good”) are cheap and offer some protection to your equipment from dirt buildup (but very little to you). Pleated AC filters offer more protection to your lungs, cost more than the cheapest, but less than the “best” filtration. The “best” filtration systems protect both you and your equipment and provide tangible health benefits – but don’t come cheap.

The bottom line: What’s important to you? If you just want to know if there is in fact a difference in AC filters, the answer is yes. 100% yes! Are high-end filtration systems and air purifiers worth it? To me they are.


The Advice Here is FREE & so is a Quote!

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about the author rich morgan


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Magic Touch Mechanical

942 West 1st Avenue
Mesa, AZ 85210
United States (US)
Phone: 4808558789

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