Influence of vertical greenery systems with different greenery coverage ratios on microclimate improvement in street canyons by scaled outdoor experiments

• Published in: Building and environment Vol. 267; p. 112158
• Main Authors: Zheng, Xiaona, Wang, Weiwen, Chen, Jinrui, Chen, Qizhou, Luo, Shuang, Wang, Hongmei, Hu, Wentao, Pan, Lan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2025
• Subjects: Greenery coverage ratios; Scaled outdoor experiments; Temperature reduction; Urban microclimate; Vertical greenery systems; Urban microclimate; Scaled outdoor experiments; Vertical greenery systems; Temperature reduction; Greenery coverage ratios
• ISSN: 0360-1323
• DOI: 10.1016/j.buildenv.2024.112158

Extensive research has emphasized indoor/outdoor thermal environments of building-scale vertical greenery systems (VGSs), yet comprehensive assessments of effects of street-scale VGSs on urban microclimates are scarce, with the relationship between greenery coverage ratios (GCRs) and cooling effects remaining unclear. This study determined the influence of VGSs on microclimate parameters in street canyons under different GCRs in a humid subtropical climate through scaled outdoor experiments. Key parameters included wind velocity (U0.25H), net radiation (Rn), urban canyon albedo (UCA), temperatures across various surfaces, namely west-facing walls (Tw-west), east-facing walls (Tw-east), and ground (Tg), as well as air temperatures (Ta). Compared with the reference street canyon without VGSs, those with GCRs of 25%, 50%, and 100% experienced reductions in U0.25H by 10%, 20%, and 22%, respectively. Increased GCR was associated with higher Rn trapping and decreased UCA. Additionally, the reductions of Tw-west, Tw-east, and Ta increased with decreasing street canyon height. Higher GCRs tended to provide greater temperature reductions, longer cooling durations, and lower daily temperature range in street canyons. The reductions of Tw-east, Ta, and the central Tg within street canyons exhibited higher values with increasing GCR, reaching maximum reduction values of 15.7, 2.5, and 5.1 °C for a 100% GCR, respectively. Notably, the reduction of Tw-west in the lower level and of Tg adjacent to the west-facing wall of street canyon with a 50% GCR reached maximum values of 15.1 and 10.2 °C, respectively, exceeding the data with 25% and 100% GCRs. [Display omitted] •Wind velocity decreased in streets with 25–100 % greenery coverage ratios (GCRs).•Streets with higher GCRs exhibited increased net radiation and decreased albedo.•West-facing wall and adjacent ground in street with a 50 % GCR showed maximum cooling.•Temperature reductions of canyon ground and air were greater with increasing GCRs.