Experimental and numerical investigation of urban street canyons to evaluate the impact of green roof inside and outside buildings

In the present work, an experimental urban canyon (scale 1:10) with 4 cm concrete wall thickness and full scale green roof was used to evaluate the impact of green roof inside and outside the buildings. The platform was equally used to validate a coupled heat and mass transfer model for green roof behavior. The albedo of the green roof was measured and implemented in the numerical model. The developed model has been coupled to a building thermal code (TRNSYS). Then, simulations were conducted for the experimental urban canyon studied where a comparison was undertaken between green and conventional roofing. A reduction of the maximum roof surface temperature by 20 °C was found in summer due to the green roof. Green roof protects the roof membrane from high temperature fluctuations increasing the roof longevity and delay the timing of the peak membrane surface temperature by several hours. Also, the presence of vegetation permits to reduce the outside air temperature of the street canyon by 0.8 °C. Hence, green roofing is an effective solution to reduce the total energy demand and to improve the urban microclimate in the street canyon for an oceanic temperate climate.