Furnace Filters

[GH85Carrera]

OK I need some help from the brain trust. My furnace filter is one of the washable - reusable types that was in the furnace when we moved in 12 years ago. I wash it out regularly and it catches a lot of crud but I want something better. I know how to use a tape measure. That filter is 20.5 x 30 inches plus or minus a 32nd of an inch. There are lots 20 x 30 filters on the market. I can't find anything that is 20.5 x 30.

What am I missing? Will a 20 x 30 filter work with a 1/4 inch gap on each side?

[MysticLlama]

Is it an electrostatic, or just a giant panel filter? How thick is it?

I would think a couple of strips of styrofoam in there to seal it up would make it fit the 20x30s just fine. You don't really want gaps as it'll let a lot of unfiltered air around the sides into the blower.

[GH85Carrera]

The current filter is electrostatic. It is just one inch thick. I was thinking of gluing a 1/4 inch dowel on each side or maybe a 1/2 inch dowel on just one side of the slot for the filter.

[MysticLlama]

Yeah, something like that would be easy and should work fine.

The electrostatics really do work pretty well if they are kept clean and the prefilters are clear, but a panel filter would catch more.

What's the current electrostatic? I tend to mostly see the Honeywells around here.

I think the problem with that is that a panel filter in order to flow enough air is usually 3-4" think and pleated (think car air filter). The 1" stuff I tend to see is the loose fiberglass sort of thing that I don't think would really catch as much as the electrostatic would in most cases.

I just had a new system put in a few weeks ago and got a hybrid, but the space it takes up would require some work on the ducting I'm sure, as it's huge.