Cooling energy saving by vegetation planting in high-density districts: Evaluation using the coupled simulation

Urban vegetation is an important factor for urban heat island mitigation, which also contributes to indoor cooling energy reduction. In this study, a one-way coupled simulation method which linked the ENVI-met and Ener-gyplus models was developed to evaluate the impacts of urban vegetation on micro-climate parameters and the building cooling energy consumptions. The simulation results from 27 cases (three typical scenarios with nine vegetation configurations) under extreme hot weather in the summer of Xi'an city, China were compared and analyzed. Compared to that in high-rise blocks, the vegetation in low-rise blocks showed a larger potential at cooling-energy saving. The maximum air temperature reduction around the buildings reached to 0.40 degrees C, the maximum mean radiant temperature reduction reached to 1.78 degrees C, and the sensible cooling load of some thermal zones dropped by 2.13%. Although the overall effect of vegetation on decreasing the district cooling load is positive, the evaporation effect and the limited area of vegetation cooling may induce a limited rate on the cooling energy saving, especially in the high-rise blocks. This study provides a method for evaluating the po-tential of environmental and energy-saving benefits of vegetation planting in different urban blocks, and the result is valuable for planners to balance the costs and benefits of green configurations.