I have never seen an add-on for an existing ducted unit, but they might exist. I do have a non-Jayco non-ducted Coleman unit that has one. I think they call it a Chill Chaser because it really does not put that much heat out at all. It uses the same 20 amp circuit that goes to the AC. If you added to the ducted system, you would have to figure out how to run another set of wires to a second thermostat somewhere unless you disabled your primary heat stat. Would probably also need a different control board because I dont think there are any provisions on it for heat strips.