This work is a multidisciplinary approach of natural ventilation in hot and humid climates. Our aim is the control of thermal comfort in tropical towns. We evaluate the natural ventilation potential of different shapes of the dense housing. We present here the result we obtained in the case of areas in chequered plan of colonial type (fig. 1). We model the quarter and simulate the airflow induced by wind around the buildings using a CFD code. This allows us to calculate the difference of pressure that appears between upwind and downwind sides of each house. From this result, we establish simple rules that can be used by designers.