A zone climate control system and method of its operation. A zone can be a single room. A method for determining which zones' vents are to be closed, and which are to be opened, in performing heating or cooling, circulation to heat or cool a zone by mixing its air with air from another zone, circulation to reduce excessive conditioning of a zone by mixing its air with air from another zone, or circulation to maintain air quality. Airflow, thermal capacity, heating or cooling requirements, and other parameters are developed for each zone by measurement and/or derivation. Plenum pressure is predicted and managed.