My solution is to enclose the cheap polyester bag filter in a large plywood box and duct the air to a vent stack on the roof. Best air quality and no expensive

My solution is to enclose the cheap polyester bag filter in a large plywood box and duct the air to a vent stack on the roof. Best air quality and no expensive cartridge filters to maintain. Not sure how practicable this is in very cold weather, but in Australia it works great.