QUANTITATIVE EVALUATION OF THE EFFECTS OF BUILT-UP GEOMETRY AND TREES ON DIURNAL AIR TEMPERATURE IN CANYON-TYPE COURTYARDS

摘要

This paper attempts to place proper emphasis on the role of urban courtyards in passive cooling. The article is a part of a larger study in preparation on the sustainability design of urban streets and courtyards on passive cooling in the urban canopy layer (UCL). The passive design control elements studied are the courtyard's geometry and the density of shade trees. The study presents the case of attached canyon-type, courtyards in residential buildings, using summer data in the Tel-Aviv metropolitan area near the Mediterranean sea coast, characterized by hot and humid climate during the summer season. Measurements of air temperature were taken hourly at 9:00, 15:00,and 18:00 h in two courtyards, situated in the same locality in Tel-Aviv. Both courtyards consist of a 20 ― 25 meter open space enclosed between two stretches of buildings of about 12 m high. Simulations were conducted for each courtyard, with and without trees, using an analytical model, the "Green CTTC model", developed recently by the authors. The simulations provide quantitative evaluation of a courtyard's diurnal air temperature pattern over the course of 24 hours. The effects of changes in the courtyard's geometry and the density of shade trees were studied by simulations. The simulated values were compared with measurements in situ. The combined cooling effect of the two studied courtyards due to trees and deepening is found to reach 4.5 K at noon out of 9 K rise of air temperature from sunrise to noon in August. The illustrations of the simulations carried out on the two studied courtyards further the importance of sustainability consideration in courtyard designs, and thus show the potentially in AC energy saving. The Green CTTC model applied to urban courtyards provides a practical tool for this purpose.