Modeling green wall interactions with street canyons for building energy simulation in urban context

Abstract

A hygrothermal model of green walls and a model of mass flows in street canyons have been proposed and implemented in a building simulation program (TRNSYS). The coupled models allow the study of the hygrothermal interaction of green walls at the interface of the detailed building model and the urban microclimate of the street. Its use highlights the effects on both urban microclimate and buildings energy loads, especially in the summer period. While reducing anthropogenic heat release, green walls set up on west or east façades mitigate the street air temperature and reduce building cooling loads depending on streets’ aspect ratio. Some of the canyon model parameters were calibrated through numerical comparison with experimental data on a reduced scale mockup. This mockup has been designed specifically to assess the green walls hygrothermal impact and to evaluate the developed numerical tools. This experimental calibration made simulating the green walls interactions with street canyons of different aspect ratios possible. The experimental and numerical results obtained with green façades underline the advantage of this modeling approach for the design of passive cooling for buildings and mitigation of excessive thermal conditions within street canyons in dense cities in warm climates.