The energy performance of two hybrid residential ventilation systems is investigated and compared to an all-mechanical system, with hybrid systems under manual and automatic control. Three different climates were investigated (Helsinki, Berlin and Paris). Results show that the energy demand of the hybrid systems is less than the all-mechanical system, with the automatic control showing larger efficiency potential. Natural ventilation is more energy efficient than mechanical ventilation for much of the year. As the legislation on energy demands is tightened, so automatic hybrid ventilation control becomes increasingly attractive.