Experimental and Theoretical Case Study on Cross Ventilation

Natural ventilation through windows and other openings in the building envelope is still the most common way to ensure the necessary fresh air supply in buildings. To date, there are few validated models for the calculation of ventilation rates through large openings. In particular, there is a lack of information about natural cross-ventilation. On the basis of an empirical study a mathematical model for the calculation of crossventilation in buildings is presented in this paper. In order to investigate the different influences on the airflow through large openings in the building envelope, measurements of air change rates under natural conditions are carried out for certain types and configurations of openings. By using the collected data, the influences of the buoyancy and wind driven airflow are analysed. The influences of the two phenomena on each other are determined in detail. Based on published numerical models for single-sided ventilation and knowledge about airflow patterns through windows, a new model for cross ventilation is derived. Again, this model is validated with the measured data. By using this new model, convection heat loss and thermal loads of buildings can be calculated more specifically.