The purpose of the Ventilation Jet (VJ) system at Dekker Chrysanten is to reduce the temperature of the grow pipe in order to save energy. Dekker Chrysanten encountered problems with circles in the crop in the VJ compartment in many cultivation rounds in 2016 and 2017. Early flowering took place at these circles, which occasionally resulted in poorer quality and shorter stems. Due to these cultivation problems, Dekker Chrysanten did not want to reduce yet the minimum grow pipe in the Ventilation Jet compartment. Due to the efforts of the growers and the monitoring project, potential causes have been identified and solved such as (1) the prevention of dry spots in the soil by: switching off the VJ when there is irrigation, switching on the VJ later in the short day period and by irrigating more (this is done companywide); (2) lowering the relative humidity setpoint in the VJ compartment at night so that a higher night evaporation is achieved; (3) improving the air flow profile of the bottom fan and (4) adjusting the climate computer software, resulting in a much more stable temperature and RH in the VJ compartment. The above learning experiences are now applied which has resulted in a good quality chrysanthemum in the past cultivation period (harvest January 2018).