The ventilation efficiency by the pressure difference of tower inside and outside, which is generated by wake formed in the leeward side of the tower or by the Venturi effect, was researched by a wind tunnel experiment and a numerical simulation. The ventilation efficiency by wake increased with the increase of wind speed, but was unrelated to the number of open windows. The ventilation efficiency by the Venturi effect increased with the increase of wind speed and of Venturi width. The numerical simulation reproduced the ventilation efficiency of the wind tunnel experiment.
