Abstract
In densely built-up area, the wind in the canopy layer is very weak, that causes the discomfort condition at the pedestrian level. In this paper, the possibility to improve the ventilation rate by changing the building height locally was investigated using the wind tunnel experiments. The ventilation rate in the narrow street was estimated by the mass transfer velocity in canyon wall that was measured by the originally devised water evaporation technique using filter paper. It was found that only small height change of wing-end building leads to the remarkable increase of ventilation rate over the whole traverse path.