In built-up area, a convective heat transfer coefficient at outside building wall is closely related to the turbulent wind affected by surrounding roughness elements. In this paper, the newly-contrived estimation method for the convective mass transfer velocity by the evaporation from the filter paper was adopted to the real scale observation at tall building windows. And the fine structures of airflow in the vicinity of windows were also measured with 3-dimensional ultrasonic anemometer (5cm span). This time, the effects on the convective transfer velocity of a protruding post near the window, the existence of balcony, and the difference of location within the building wall were especially examined. The linear regression equations between mass transfer velocity and the wind speed at the one and half of the building height were derived for the windward condition and leeward condition, respectively. These equations were slightly changed dew to the location and surrounding conditions, but its variation range was restricted within 25%. As for the wind speed at the distance of 30cm from the surface, its only one regression curve to the mass transfer velocity was possible to determine for all observation points.
