Comparison of Two Ventilation Control Strategies in the First Passive House Standard Norwegian School

Abstract

The perceived indoor climate resulting from two ventilation control strategies was evaluated in a classroom of the first school built according to the Norwegian passive house standard.Both strategies consisted in varying the ventilation rate according to room demand, ie. Demand-Controlled Ventilation (DCV). The existing strategy consisted in varying the ventilation rate in order to maintain a constant carbon dioxide concentration of 800 ppm in the classroom (constant-CO2 DCV). A new strategy was implemented which consisted in a combined CO2 and temperature DCV, ie. to control towards a proportionally lower CO2 concentration when the indoor temperature increases. The aim with this strategy was to address both overheating and the fact that perceived indoor air quality decreases when temperature rises.Indoor climate measurements, as well as questionnaires on the perceived indoor air quality and thermal comfort filled up by the pupils were used to compare both strategies. The data from the questionnaires were then analyzed using a random effect linear regression model. The regression analysis revealed that the initial ventilation strategy was responsible for discomfort resulting from too high variations in the indoor temperature. The new combined CO2 and temperature DCV strategy provided a perceived indoor climate which was significantly better than the existing strategy.