Natural ventilation in urban environments.

The present paper discusses issues related to the potential of natuml ventilation techniques whenapplied to urban environment and in particular to buildings located in canyons. The paperdiscusses the specific phenomena related to air flow prcmsses in urban cauyons and presentssome of the existing methods to calculate the wiad speed distribution into the canyons.Wind speed and temperature data have been collected through experiments catried out in tendifferent urban canyons presenting different characteristics, during summer 1997. The collecteddata have been used to evaluate the potential of natural ventilation in the ten canyons for smgleand cross ventilation codgurations. It is found that, mamly during the day period, his isseriously reduced because of the important decrease of the wind speed inside the canyon. Airflow reduction may be up to ten times the flow that corresponds to undisturbed ambient windconditions.