Nonaka, T.; Kurabuchi, T.; Ohba, M.; Endo, T.; Goto, T.; Kadowaki, Y.; Kawase, T.
Bibliographic info:
The 6th International Conference on Indoor Air Quality, Ventilation & Energy Conservation in Buildings IAQVEC 2007, Oct. 28 - 31 2007, Sendai, Japan

This study is focused on the efficient use of cross-ventilation in a densely populated area by using roofwindows in particular. Wind tunnel experiments were conducted to understand not only the relationbetween the building coverage ratio and the coefficient of wind pressure (Cp) but also the relationbetween the roof slope of a residence and Cp value. To simulate an urban area, dummy models wereplaced around a target model, and the building densities were set to 0, 10, 20, and 40%. The roofslopes of residences were set to 0 (flat roof), 15, and 26.7. The Cp distribution on the surface of eachresidential model was measured. The tangential dynamic pressure at the openings was also measuredto predict the cross-ventilation rate (Q value) by using a local dynamic similarity model, and thecalculated Q value was compared with the experimental value. The experiments and calculationsrevealed the following information: (1) the overall Cp value of a flat roof residence approaches zerowhen the building coverage ratio increases; (2) a negative pressure is maintained near the ridge of aleeward roof, even if the building coverage ratio increases to 40%; and (3) the efficient use of thenegative pressure near the ridge on the leeward roof can improve the cross-ventilation rate in a denselypopulated area.