Comparing predicted and measured passive stack ventilation rates.

BRE have experimental data for the flows found in Passive Stack Ventilation (PSV) ducts from a test house in Garston. These data cover different duct diameters, number of bends and roof terminals, all measured over a variety of weather conditions. In the first part of this paper the data are analyzed to separate temperature and wind effects, and to see how well they fit well to the expected model of duct flow. The second part gives a comparison of the same data with predictions from the single zone ventilation model BREVENT. Extensive research at BRE has improved the modelling of PSV ducts within this computer model, and this new information was used to try to calculate the flows in the duct for the measured weather conditions. The results show good correlation between the predicted and measured duct flow velocities. Care was needed in identifying the effective volume of the building to give this good result. More work is needed on the interaction between PSV flow elements, and whether using a multi-zone model would give better results.