New buildings have to satisfy ever-tightening standards regarding energy efficiency and consumption. This results in higher insulation levels and lower air leakages that reduce heating demands. However, even at moderate outdoor temperatures these buildings are easily warmed up to such a degree that in order to ensure acceptable indoor environment quality, removal of excess heat becomes unavoidable. Use of electric energy related to mechanical cooling is considered incompatible with achieving zero energy buildings (ZEB). The use of ventilative cooling (VC) in combination with mechanical cooling means energy consumption reduction due to lower use of mechanical ventilation and cooling system.
This paper examines the application of ventilative cooling solutions in cold climates through simulations of an existing detached single family house in Norway, the ZEB Living Lab at NTNU/SINTEF. The house has computer controlled motorized windows. This will enable natural ventilation in some part of the year and could then reduce the energy use of fan power. The openable window are placed at the north and south facades and this enables considerably cross ventilation and also stack ventilation as some windows are placed four meters high.
IDA ICE program will be used to calculate the energy consumption of the baseline simulation: demand controlled ventilation with variable air volume and mechanical cooling. By means of using CONTAMW the airflow profiles while using controlled window opening are calculated and used as input profiles in IDA ICE to calculate the energy consumption while using hybrid mode ventilation.
Results show significant energy savings when using ventilative cooling. Due to the low outdoor temperatures in Norway the use of ventilative cooling remove mechanical cooling demands almost completely. The reference for comparison has been the European standard EN15251 (class II).
Ventilative cooling is proven to be relevant in combination with mechanical ventilation and will be crucial to achieving energy targets for new zero energy buildings while the indoor climate is maintained.