Computer-Aided Simulation on the Impact of the Combination of High-Rise Building Wall and Roof Green Coverage Ratio on Urban Microclimate

Abstract

Environmental issues related to global warming and urbanization are becoming more serious. Many studies have shown that urban vertical planting can effectively reduce ambient temperature. However, the impact of different vertical planting combinations on urban microclimate has rarely been studied in Taiwan. Thus, in this study, the impact of different proportions of green walls and green roofs on the environment is explored. Referring to 6 times 6 high-rise buildings of 90 m in the ideal city. FLUENT was used to simulate the average climatic conditions of the Taipei Station in the past ten years’ summer. Since the actual building has openings that cannot reach 100% vertical plant coverage, the coverage is calculated based on the proportion of the green coverage area to the area of bare walls and roof decks. We had four options, including case 1 without greening, case 2 (green wall 25% + green roof 75%), case 3 (50% green wall + 50% green roof), and case 4 (75% green wall + 25% green roof). The research results show that at the height of the pedestrian layer (1.5 m), the wind speed of urban streets is reduced due to the obstruction of surrounding buildings. The installation of wall greening slows down the wind speed and reduces the ambient temperature, which is better than roof greening. In the urban canopy (90.5 m), as the Z-axis height increases, the higher the green roof ratio, the higher the wind speed. To improve the overall urban wind below 100% of the total greening balance of walls and roofs, it is recommended that wall greening be 50–75% and roof greening be 25–50%.

Keywords

• urban microclimate
• high-rise building
• vertical greening
• green coverage ratio