A hybrid ventilation system combines both mechanical and natural ventilation modes. The natural ventilation mode, especially, causes some challenges for analysis tools since the varying nature of naturally driven flow means that transient calculations should be used to predict the flow fields. Analysis tools based on CFD have some advantages for detailed investigations since, in addition to evaluating the flow and temperature fields, it is possible to use CFD methods to calculate air exchange efficiency and other flow indices.
A publicly-owned office building in Eskilstuna, Sweden, has been retrofitted with high-frequency with self-regulating controls for the lighting and ventilation systems. The building has a total floor area of 19,000 m2 and contains more than 3 00 offices, a conference room, lunch rooms, and a recreation hall. Before retrofitting the total annual electricity consumption was 1/300 MWh and the district(heat consumption was 950 MWh. The total annual energy consumption was reduced by 20% as a result of the new installlations.
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