Hey HVAC people, is this as bogus as I think it is?
August 4, 2024 6:05 PM   Subscribe

Is this air filter as bullshit as I think it is?

Our condo building has a contract with some company to come around once a year and service our in-unit air handlers, to keep them under warranty or something. This seems to involve vacuuming the coils and replacing the filter. Previously the filter has been the typical pleated paper with cardboard surround, but this time it's this .... I swear to god it's something someone made in a garage out of hardware wire, polyfill and a sewing machine. There's no label on it, no manufacturer, and it's just ... it's not going to filter anything but cat hair.

What do I tell the building management about how bullshit this is? Assuming they don't already know. Assuming it's bullshit. Because it certainly triggers my bullshit sensor.
posted by seanmpuckett to Home & Garden (10 answers total) 2 users marked this as a favorite
 
I've seen similar ones in my building, it's obviously not HEPA but it'll pickup dust well enough.
posted by tiamat at 6:11 PM on August 4, 2024


I'm not sure what your question is. Is it a great filter? No. Is it a filter? Yes, here's a similar one you can buy right now. Here's another.

If you'd like the company to use a better filter, you should ask them to install a MERV rated filter. MERV 11 is pretty easy to get, and not much more expensive than alternatives. MERV 13 is also easy, but adds a bit of cost.
posted by saeculorum at 6:22 PM on August 4, 2024 [2 favorites]


Best answer: My understanding as a homeowner who doesn't know anything about your HVAC system.

These kinds of filters on air handlers are supposed to prevent dust from being sucked up into the air system and shortening the life span. As a secondary effect they may improve indoor air quality. A filter that is designed to filter out very small particles, like a HEPA filter, may actually cause too much back pressure on a system and will also shorten life.

If you're concerned about indoor air quality then a separate HEPA filter is a good idea. We have both an expensive Coway unit and a cheap $20 diy box fan filter.
posted by muddgirl at 6:53 PM on August 4, 2024 [4 favorites]


Sorry I didn't answer your actual question. That is probably the minimum cost air filter required by the HVAC warranty.
posted by muddgirl at 6:54 PM on August 4, 2024 [1 favorite]


Best answer: There are two ways to think about the function of an inline HVAC filter, and to some extent they are in opposition to each other. The first is as protection for the blower motor (catching cat hair and other stuff that would clog up the fan, basically), and the second is to clean the air you breathe. On preview, as muddgirl described, a filter that does a better job cleaning the air (a higher MERV rating) can restrict airflow enough to stress the fan motor and shorten its life by making it work harder. This filter is serving the first purpose and not the second.

HVAC systems designed to get around this problem use thicker filter media, usually 4", so there's a lot more pleated surface area to do the filtering, allowing a filter that still does a pretty good job of cleaning the air to not compromise the fan motor.

My opinion on this as the owner of a furnace with a 1" filter is: use a less-restrictive filter in the furnace and add dedicated air filter devices in your rooms to clean the air. You can also use a manometer to test the static pressure in your HVAC system and find the sweet spot between the two functions. For us it was MERV 9.
posted by pullayup at 7:00 PM on August 4, 2024 [5 favorites]


Best answer: I am not an HVAC expert.
A friend who suffers from respiratory issues moved to a recently remodeled apartment with a newly installed air system which featured a filter very similar to the one you pictured.
Wishing to give my friend a better breathing environment, I replaced that “clearly inadequate” filter with a HEPA rated one. We were told that putting in a HEPA filter would void the warranty on the brand new HVAC unit. I looked up the HVAC unit’s model number on their website, and sure enough, it voids the warranty to use a HEPA filter.

So the very porous non-HEPA filters are just to protect the blower motor components by straining out big particles like cat hair. Your buildings’ contracted service is likely a way to make sure this needful routine maintenance happens.

Wholeheartedly agree with muddgirl and pullayup above that you let the air system function as it is designed for with the existing “polyfil” filter, then supplement it with standalone HEPA rated units to achieve the indoor air quality you seek.
. . . .
It would be a better, cleaner, indoor air world if manufacturers would incorporate a more robust fan mechanism that allowed for higher MERV-rated HEPA filters to be used.
….

And, yes, the $20 box fan with taped on HEPA-filter models can achieve astounding results — performing admirably alongside their $300 cousins.
posted by tronec at 1:11 AM on August 5, 2024 [3 favorites]


Response by poster: Wow, thanks. I learned stuff today! Love a day like this.
posted by seanmpuckett at 5:07 AM on August 5, 2024 [1 favorite]


I'm not an HVAC person, but I inspect HVAC system on occasion in connection with mold inspections.

Every HVAC system is going to have a maximum MERV rating that it can handle. The higher the MERV rating, the finer the particles it will be able to filter, but also the harder it is for the system to pull air through it. If you use a higher rating filter than your system is designed for, it's going to cause some kind of overload in the system at some point, which is why using a HEPA filter is would void your warranty (unless you are in a medical facility, the HVAC system is almost guaranteed not going to be able to handle a HEPA filter.)

That filter in the picture though, looks extremely thin and flimsy, unless it's some unusual material with static properties or something. I would think you could at least ask your landlord what it's MERV rating is, and what the system is designed for (ir if you can find the model for the equipment, you may be able to look it up depending on how complicated it is). For an apartment, normal MERV rating used could be anywhere from 5 to 11, depending entirely on the age of the building, the HVAC design and how much the landlord is willing to spend. A few might be able to manage a Merv 13, but that's not common. (Caveat that I really only deal with commercial systems, so my knowledge of residential ones is largely from general research/industry background versus firsthand.)
posted by Dorothea Ladislaw at 8:39 AM on August 5, 2024 [1 favorite]


I want to add, just in case, that these filters almost certainly should be changed more than once a year, whether they are pleated or these static media filters. Pleated is at minimum every 3 months, these filters are usually monthly.
posted by muddgirl at 8:41 AM on August 5, 2024


My opinion on this as the owner of a furnace with a 1" filter is: use a less-restrictive filter in the furnace and add dedicated air filter devices in your rooms to clean the air.

This is exactly what our HVAC service person told us the last time they were here, and it's what we do.
posted by bluesky43 at 9:49 AM on August 5, 2024


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