Abstract: The present application discloses a method of converting a single zone HVAC system to a multi-zoned HVAC system. More specifically, the present application discloses coupling at least one interface module to at least one controller of a heating unit, cooling unit, and blower assembly. Further, at least one thermostat may be positioned within each desired zone of a multi-zoned structure. The user may then position at least one register on at least one terminus of a duct within each zone. Thereafter, each thermostat within each zone is associated or linked via a communication channel or network with at least one register within the same zone, thereby forming at least one thermostat/register regime within each zone of a structure. The interface module may then be associated with the various thermostat/register regimes.