A Demand Controlled Hybrid Ventilation System is a two-mode system using natural forces as long as possible and electric fans only if necessary. Sensor technologies are used to establish the exact required airflow for indoor air quality and thermal comfort to a minimal energy demand. A large part of the Dutch dwellings are foreseen with a ventilation system consisting of natural supply with mechanical exhaust. Fan power for these systems typically is 30 - 40 W (Specific Fan Power 0.7 - 1.0 kW/(m3/s)). Small improvements lead to a laboratory reference of 21 W.
In France, most of the ventilation systems in dwellings now consist of exhaust vents linked up with a fan, and air inlets. A survey conducted by the CSTB shows that actual ventilation rates are frequently different from prescribed values and that a lot of problems encountered are related to occupant behaviour, - The duration of exhaust flowrate peak value was measured ; it was shown that this duration was dependent on the kind of command and its location in the room. - draughts through air inlets were a major concern. - a lots of air vents did not operate correctly because of fouling.
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