Window ventilation efficiency in the case of buoyancy ventilation

•We measured the ventilation performance of a number of different window types under buoyancy ventilation.•We differed between the resulting mass flow and the resulting CO2 removal rate as performance indicator.•CO2 stratification was typical for window types and influenced the performance significantly.•Stratification must not be ignored for the evaluation of performance.•Horizontal Pivot Windows performed best, Tilt Windows performed worst, between them was a factor of 2 to 2.5.

This paper presents the results of a number of measurements that were carried out in order to quantify the ventilation efficiency of different types of windows under buoyancy ventilation. The tested window types were double vertical slide window, turn window, tilt window, awning window, horizontal pivot window and vertical pivot window. Each testing of these types comprised different opening rates, so that the performances could be compared across a wide range of window states. Performance criteria were the mass flow, the air change rate and the CO2 removal rate, each of them normalised to a temperature difference of 1 K. The horizontal pivot window turned out to be the best performing type of window.