Evaluating the collective effects of vertical and ground greening on microclimate and energy consumption in a high-density building array

Previous studies attribute the energy-saving potential of vertical greening primarily to reducing the building surface temperatures (T_se) in isolated buildings or simple street canyons. However, its performance in high-density building arrays remains unclear, where inter-building effects and collective greening significantly change the microclimate. To address this gap, eight scenarios across two spatial scales—an isolated building and a 3 × 3 array—with different configurations of vertical and ground greening are systematically evaluated using a one-way coupled simulation that includes ENVI-met and EnergyPlus. This study quantifies the collective effects of various greening configurations on the microclimate and building surface temperatures (T_se). Furthermore, we analyzed the total building energy savings (ΔE) to assess the relative contributions of reducing T_se and ambient air temperature (T_a). The results indicate that over 97% of the energy savings are attributed to the reduction in T_se. While array-scale vegetation improves the thermal environment, it provides limited benefit to building energy consumption. Beyond the vertical greening of the target building, the collective cooling effects from surrounding vegetation contributes about 1.2% to additional energy savings. These results confirm that façade-level thermal shielding is the primary driver for energy savings, significantly exceeding the impact of ambient air cooling. Additionally, the improvement of array-scale microclimate requires multi-dimensional, collective greening strategies. This study provides a quantitative foundation and meaningful references for optimizing vertical greening arrangements to achieve both building energy efficiency and urban environmental sustainability.