Energy consumption and comfort of modern air conditioning systems for office buildings.

Selection of an air-conditioning system is generally determined by the sensible heat load of the building, as the total of external and internal loads. 3 systems with a mean specific sensible heat load of 60 w/m² floor area are compared. System 1: VAV-system, representing a turbulent mixed flow ventilation. System 2: Air-water induction system with ceiling induction units, representing a combined turbulent mixed flow - displacement flow ventilation. System 3: Chilled ceiling system combined with displacement ventilation. Comparing these 3 systems there is little difference in energy consumption, if they are well designed and correctly operated and the room air temperature is allowed to float freely within a zero energy band. The difference between fixed and floating room air temperature is higher (10 %). Futhermore the important influence on comfort and energy consumption of typical user faults, of wrongly designed or poorly adjusted VAV-systems and of poor maintenance is shown.