Experimental and theoretical analysis of natural ventilation by means of windows opening.

The purpose of this paper is to improve our understanding of the transient behaviour of airing by window opening. While a few simple models exist to analyse the results of window opening, its transient behaviour is not yet well understood, in its effects on air change rates, air temperature and ventilation efficiency. The paper achieves its purpose in the first place by using a synthesis of numerical modelling activity. Then a critical analysis of the methods of calculation is undertaken, comparing both detailed (CFD) analysis results and simplified or zonal models predictions. There is a comprehensive discussion of the limitations, features and applications of each model. A comparison is made of the performance of theoretical models with obtained by a full-scale measurement campaign. Through these methods, a simplified procedure, based on charts and non-dimensional groups, is suggested to give designers a quick way of evaluating the ventilation rate through an open vertical window.