1. A controller for regulating the temperature within a building that controls the use of a whole-building ventilation apparatus as an alternative to HVAC system by reacting to outside and inside conditions, wherein said controller comprises: a. an internal sensor that monitors temperature in the building, b. an outside sensor that monitors current outside air temperature, c. a whole-building ventilation apparatus comprising a building exhaust duct, housing at least one damper and fan that determines air flow out of the building, d. a microprocessor system that sets logical set-points based on mathematical algorithms that uses the said internal and external sensor, e. a series of switch relays controlled by the said microprocessor system that determine whether calls for cooling or heating are directed to the said whole-building ventilation apparatus or HVAC system.