We currently live in a 3200SF home serviced by 2 HVAC's. We are in the process of relocating to a similar climate and don't want to go back to a single HVAC. We are looking for a similar sized house or bigger. We believe the two zones offer great advantages to one. My question is: If we found a house that didn't have two separate units, is it possible to retrofit a house to have two separate zones and units?