A three dimensional computational fluid dynamics (CFD) model is presented to investigate effective parameters on cross ventilation and air flow pattern inside a building. The numerical methodology is based on the finite volume numerical solution of the Navier-Stokes equations, using the CFD commercial code FLUENT. Numerical results are validated with available experimental data. Different opening position and shape configurations are used to investigate effect of position and shape of openings on the flow pattern inside the building. It is shown that openings can determine behavior of flow stream inside the building and designers can use them to increase natural ventilation efficiency of the building and control the recirculation zones which are formed in different rooms. (C) 2015 Published by Elsevier B.V.