hepa retrofit

Is there a way to retrofit furnace ducting to change from your standard 1" furnace filter to a HEPA filter? All of the stuff I could google shows auxiliary units that filter a portion, and are a bit pricey. What I'm looking for is a kit that takes the down return air (10x24 i think) and jogs it over to accommodate the ~6" thickness of a HEPA.

Thanks,

I've only seen a couple of these, and it usually ends up with the sheet metal shop custom making ducts to allow the proper installation...I kind of doubt anyone makes a generic retrofit kit.

If you are lucky, your air handler input may take the output side directly, then you'd have to adjust the incoming duct to fit the filter.

Check the back pressure the filter produces, it may put a big strain on the fan, and you may need to adjust the speed to end up with the desired/needed flow rates to maintain the heating/cooling efficency. Expect the fan to have a shorter life; my unprofessional opinion.