DIY HVAC furnace Filters?

Anyone done any testing of use of DIY (fabric, presumably) furnace filters.
A good furnace filter in Canada is like $50, and single use. But if I willing to pleat my own fabric, I might be able to do better???

Anyone have any experience with this, or maybe even enough experience with fabric for recommendations. I heave heard of felt for liquid filtration. I have heard of nylon stockings so maybe a bolt of that material.

If it's washable, and you are willing to keep up on doing so, it might not need to be pleated. The point to the pleats, as far as I know (someone else may know better than me)  is to increase the amount of filtering space, making it last longer.
You might find it very worthwhile to look up the history of furnace filters, and learn why they are made the way they are, and decide what features you need most in a filter.

That said, I found a type of filter that is green tangled plastic stuff (like a green scrubber for dishes) that can be cut to size, that I put a mesh cover over, it gets washed quite often, and is always filthy, I assume it's trapping a lot of crud. I also live in a rental with ductwork that is filthy, so it's hard to make the intake air much dirtier than the ducts will make the output air. I have mesh in many layers over the output ducts, and that gets filthy too.

My criteria for a filter is inexpensive, washable, and keeps the worst of the filth out. Fine filtering is a waste of time here, and the disposable filters crud up way faster than they claim to last. 8 layers of the mesh seem to do a fair job.

Look up why your filter is the way it is before making any decisions. It might affect the efficiency of your system adversely to change the flow rate.

:D

Howdy!
I used that plastic tangled green filter stuff (it also comes in blue for whatever reason) for years as a filter for the heat pump/furnace A/C. It works, though I won't vouch for how well.
It was easy enough to wash it out on a semi-regularly basis, I used a garden hose most of the time - spray it clean and let it dry.

We switched to the one-use filters some years ago and I can't say they're necessarily any better. I'm sure they trap more stuff, and they need to be changed more frequently.

I'm going to go look at the reusable ones again. Layering them, and/or wrapping them in something would probably work pretty well.
I did find a source for the nylon stocking material, but it's not a supplier I have ever used before, and it's a "Global Clearinghouse"  so I probably won't ever order through there.

Otherwise? If the filter is washable, or made in such a way as to be easy to try and replicate, I would say try it.
The worst that happens is that it doesn't work and you spent money to buy materials that can't be used for that purpose.  

The layering of fiber-y stuff and a different type of filtering material should work to some degree, it's just a matter of how well. Experimentation is probably your friend in this.
Good luck!

Thanks for the suggestions. But I am particularly worried about creating too much static pressure, so do want pleating. Surface area is directly corelated to how much pressure it blow air.

Jon Wisnoski wrote:Thanks for the suggestions. But I am particularly worried about creating too much static pressure, so do want pleating. Surface area is directly corelated to how much pressure it blow air.

In that case, you need to use the same type of material they do, because it's calculated for the amount of airflow that particular material allows through it. Different fabrics allow differing amounts of air to pass through.

Depends on what you are filtering for.

You might want to experiment with making the filter more sticky with like hair spray....

Also, you do not want to restrict the airflow too much in the furnace as that will great affect it's efficiency.




I was thinking one could take a cheap filter and make it better by spraying sticky (hairspray ) and increase  it's value...

The other suggestion is to get a re-usable one  as was already suggested.

  Another option..

I love project farm --->

Good heavens Jon, where are you buying your filters? I'm spending under $37 CAD for 4-packs of Costco 2200 top-of-the-line single use filters. All the HVAC guys I have talked to say these are as good or better than top shelf 3M. My experience (forced air heating for 6 months of the year) is that they are excellent.

This may be a contrarian view, but frankly, my experience is that cheaping out or improvising furnace filters has a very negative impact on indoor air quality. Once bio-goo gets into the duct work, it creates a nice moist factory for allergens from dust mites and mold. Since Dear Wife and I both have allergies, dirty ducts make us miserable for six months of the year. Duct cleaning is bloody expensive.  There are much better places to economize. My 2c.

@Douglas Alpenstock: I have been looking online, and I did mean the 4" or 5" year long (or 3 months depending on who you ask) filters. If I look at Costco online I think I see what you are talking about but is shows $45 for me for a years worth. So around what I was talking about. You are right it is not horrible, but I disliked disposables in general.

During some of our very smoky NW fire seasons, i've had very good success with blue Zep shop towels. I created a layer of blue shop towels on the back of a box fan. Then I created a "manifold" of sorts and sealed the edges. The fan blows in to create positive air pressure (which helps prevent air from getting in other places. Since the air coming in is going through the shop towels the air is filtered somewhat. I remember reading somewhere that zep towels actually filter down to 1-3 microns, which is more than plenty to catch smoke particulate. Anyhow, worked for my use case.

The issue with pleats is about surface area. 1) it provides higher flow for a given cross section, and 2) the filter doesn't need cleaning/replacement as often since there's more filter for the area. This is why higher-end car air filters are massive with many pleats so the car gets all the O2 it needs to combust well, even at higher RPMs.

There's lots of research done on Zep towels, and other filter media, relating to DIY masks during C-19. Consider that some otherwise unacceptable filter media (fabrics) may become viable if sprayed with a sticky substance (reduces the size of filtered particulate) or if it can remain wet. In fact, where electricity is an acceptable input, a small water pump circulating water over the media may be self cleaning and allow the use of cheaper media. That being said, it would increase the humidity of the space. But if that's a desirable bi-product, then maybe an interesting option. Swamp cooler/filter.