Got a large closet for the rack or can you add a space heater to the room? Or use full size wall insulation board panels and duct tape to build a total surround enclosure closet around the rack? Your temps are too cold for heat tape. Even if you ran 2 sets to cover the entire floor surface at the low and high temps, an air temp of 50-60 will be far too cold for the tape to increase the ambient enough to avoid respiratory issues.