This paper compares the application of hybrid window ventilation through validated IDA ICE simulations of an already existing kindergarten in Norway to simulations of the same kindergarten using DCV and VAV (both without cooling) and exhaust fan and only window controlled natural ventilation(these two last with night set back allowed). Results show important energy savings when using ventilative cooling as outcome of the low outdoor temperatures and the same applies for night cooling. Regarding thermal environment and indoor temperatures, for really warm days, it is hard to sustain acceptable temperatures without the use of night set back or mechanical cooling.