Abstract: An air filter assembly and method of using the assembly are described. The assembly can include a filter media cartridge and a filter frame connected to the filter media cartridge. The filter media cartridge can have a cartridge body defining an internal volume, an aperture in a wall of the body, a supply roller for supplying filter media, and a take-up roller for receiving the filter media. The filter frame is configured for an air handler filter slot of an HVAC system. The filter media can extend about the longitudinal axis of the filter frame from and back to the filter media cartridge such that a double layer of the filter media covers an air flow opening defined by the filter frame. The filter frame can have a pair of side frame sections, each having an expansion joint that allows the side frame section to be lengthened or shortened.

Abstract: An air filter assembly and method of using the assembly are described. The assembly can include a filter media cartridge and a filter frame connected to the filter media cartridge. The filter media cartridge can have a cartridge body defining an internal volume, an aperture in a wall of the body, a supply roller for supplying filter media, and a take-up roller for receiving the filter media. The filter frame is configured for an air handler filter slot of an HVAC system. The filter media can extend about the longitudinal axis of the filter frame from and back to the filter media cartridge such that a double layer of the filter media covers an air flow opening defined by the filter frame. The filter frame can have a pair of side frame sections, each having an expansion joint that allows the side frame section to be lengthened or shortened.