A modular duplex media handling system is installable for use with a print recording system having a simplex media handling system. During first side printing a media sheet is fed along a first media path in the simplex system from feed rollers to metering rollers and into a print zone. After first side printing and prior to releasing the media sheet, the metering rollers feed the media sheet back along the first media path to the feed rollers. The feed rollers in turn feed the media sheet completely into the duplex module where the media moves along a loop path (in effect flipping the media sheet). The media sheet then is fed back to the feed rollers and along the first media path for second side printing. A humidity sensor in the duplex module signals to the print recording system whether the duplex handling system is installed.