Natural ventilation is widely applied to new building design as it is an effective passive measure to reach the Net Zero Energy target. However, the lack of modelling guidelines and integrated design procedures that include technology solutions using passive design strategies to exploit climate potential, frustrate building designers who prefer to rely on mechanical systems. Within the existing natural ventilation modelling techniques, airflow network models seem the most promising tool to support the natural ventilation design as they are coupled with the most widely used building energy simulation tools. This PhD work provides methods to integrate natural ventilation in the whole building design and to improve natural ventilation predictability overcoming some of the barriers to its usage during early-design-stages, such as model zoning, input data estimation, model reliability and results uncertainty. A sensitivity analysis on parameters characterizing different natural ventilation strategies has been performed on a reference office building model considering key design parameters that cannot be clearly specified during early-design-stages. The results underline the most important parameters and their effect on natural ventilation strategies in different climate types. The airflow network modelling reliability at early stage design phases has been tested by comparing early-design-stage model results with output results from a detailed model as well as with measured data of an existing naturally ventilated building. Results underline the importance of an optimized control strategy and the need of occupant behaviour studies to define better window opening control algorithms to be included in building dynamic simulation tools. Early-design-stage modelling caused an overestimation of natural ventilation performances mainly due to the window opening control standard object implemented in building dynamic simulation tools, which assume all the windows within the same zone are operated at the same way. With sufficient input data (identify in the research work), airflow network models coupled with building energy simulation tools can provide reliable informative predictions of natural ventilation performance. Finally, natural ventilation design guidelines are proposed to explain how existing design tools and methods can be applied within the whole design process, taking into account technology solutions for triggering the natural ventilation.