Home air filtration

[Dennis Leahy]

There isn't a sub-forum for air filtration, so I plunked this in with Food & Water on the Off-Grid forum.

Because active air filters are so expensive , and because my 1960's house circulates a lot of dust, and because I am a do-it-yourselfer, I am in the process of making a couple of active air filters. [My house has the typical air filter on the input side of the air handler, and I have tried Merv 5, 8, 11, 13, and electrostatic filters. I still have dust circulating. I do plan on also feeding a long flexible vacuum tube, probably with a whiffle ball attached to the end, and shove it down all the air ducts, but right now I'm concentrating on making some air filters.]

Variations on home-made air filters using a box fan and commercial furnace filters can be found on youtube.

What I'm doing is to construct a cube, with a solid (thin plywood) bottom back and top, with a round hole cut in the top that fits a small 12" circular fan. Besides the plywood back, the other 3 walls (sides and front) are commercial furnace filters. (Merv 8, 20 x 16 x 1) The overall filter will be 20" tall, with the fan on top pointing up, so each side is 16".

What I'd like to do is to then cover the 3 filters with fabric - a pre-filter for the filters. Removable, vacuumable, and washable. Otherwise, the filters will just get clogged and I'll have to replace $21 worth of filters on each of my homemade air filtration units, too frequently.

Something similar is a filter "sock" used in pool skimmers, if you are familiar with those, but the available ones are too small. If I just wrap fabric around the 3 filters, that would be a piece of fabric about 48" wide and 20" tall. This sounds like the best option to me, so I went onto a fabric retailer website... and realized I have no idea what I'm doing.

I don't know much about fabric. I don't want fabric that is too tightly woven and will drastically restrict the air flow, nor do I want something like netting with big holes that will make the pre-filter nearly worthless. I also think I don't want a 'plastic' fabric, as I'm thinking it will emit tiny pieces of microplastic, but then again, I could have that all wrong and maybe a plastic (polyester, etc.) fabric will become electrostatic with the air movement and grab more of the dust.

Based on that description, and going after something cheap, do any of you have experience or insights into fabric, and could help pick out a fabric to purchase?

Thanks in advance for any help.