A neighbourhood-scale estimate for the cooling potential of green roofs

Ivo Suter, Čedo Maksimović, Maarten van Reeuwijk

Urban Climate · 2017

Abstract

Green roofs offer the possibility to mitigate multiple environmental issues in an urban envi- ronment. A common benefit attributed to green roofs is the temperature reduction through evaporation. This study focuses on evaluating the effect that evaporative cooling has on out- door air temperatures in an urban environment. An established urban energy balance model was modified to quantify the cooling potential of green roofs and study the scalability of this mitigationstrategy.Simulationswereperformedfordifferentclimatesandurbangeometries, with varying soil moisture content, green roof fraction and urban surface layer thickness. All simulations show a linear relationship between surface layer temperature reductionDT s and domain averaged evaporation rates from vegetationmmW, i.e. DTs = eW • mmW, where eW is the evaporative cooling potential with a value of∼−0 .35 Kdaymm−1. This relationship is independent of the method by which water is supplied. We also derive a simple algebraic relation foreW using a Taylor series expansion. © 2017 Published by Elsevier B.V.