Roof air is cetainly becoming the norm. Millenium builds nothing else, most Marathons 2004 and newer and now Liberty (gasp). Properly ducted roof air combined with OTR air has proved to us that it can comfortably handle triple digit temps on the road or parked. Owners with older coaches who think their roofs are too noisy, can fairly easily and relatively cheaply retrofit to the newer and quieter (quiet enough for Liberty) units. That will also let them go from 13,500 to 15,000 btu.