Auxiliary environmental control in passively cooled buildings.

The need for auxiliary heating and cooling systems in European buildings is established on the basis of building physics and climatic conditions, emphasizing that cooling systems may not be needed in most regions if there are no large internal gains and the building envelope is well designed, through the use of bioclimatic design principles. Occupant attitudes and the consequences upon indoor environmental quality are also compared for the cases of actively and naturally controlled buildings. Ways to optimize the energy and functional efficiencies of mechanical cooling systems are then discussed, including the cooling-producing equipment, distribution networks and control strategies. Finally, the major difficulties that now exist in modelling, sizing and designing HVAC systems are also presented, pointing out some topics for future research and standardization.