Is High Urban Landscaping or High Urban Albedo More Effective for Urban Heat Island Mitigation? : Simulation Analysis on Effects of Urban Landscaping and High Albedo Envelope on Urban Microclimate in Osaka

Urban planning, building design and landscaping can all provide strategies for the urban heat island (UHI) mitigation and directly affect people’s living environment and thermal comfort. In order to better improve the urban microclimate through rational building envelope design and landscaping, an example of a new residential area with 10,000 m2 floor area located in Osaka, Japan is examined. The effect of urban green covering (UGC), urban albedo (UA) and urban aspect ratio (UAR) on urban microclimate was investigated with the environmental simulation, ENVI-met. A total of eight scenarios with UA of 0.3 and 0.7, UGC of 0%, 20% and 40% and UAR of 1.8 and 0.9, were simulated. Among these scenarios, the scenario simulated with low UA of 0.3, UGC of 20% and UAR of 1.8 has the greatest potential in improving urban microclimate. Comparing the scenarios with UAR of 1.8 and 0.9, it indicated that the scenario with large UAR is more effective than that with small UAR for UHI mitigation. Additionally, in the case of smaller UAR, diffusive highly reflective (HR) facade will not improve the UHI effect, whereas it might increase the UHI phenomenon in Osaka.