Integrated effects of overhanging shading devices and aspect ratios on microclimatic performance in street canyons: Scaled outdoor experiments

ORCID

Abstract

Overhanging shading devices (OSDs) are increasingly implemented to improve thermal comfort. Yet, the effects of street-scale OSDs on ventilation, thermal, and visual comfort under different canyon aspect ratios (H/W) remain unclear. This study conducted scaled outdoor experiments in a subtropical city to investigate the coupled effects of OSDs and H/W on street-canyon microclimate. OSDs reduce canyon wind speed by 25% and 52% for H/W = 1 and 2, respectively. The cooling is concentrated mainly beneath the OSDs at both canyon sides. The maximum reductions in east-facing and west-facing wall temperatures at 0.15 m height (pedestrian level) are 9.7 °C and 10.6 °C for H/W = 1, respectively, compared with 4.5 °C and 4.4 °C for H/W = 2. At the west-facing side, pedestrian-level air temperature decreases by 1.8 °C for H/W = 1, but increases by 1.4 °C for H/W = 2. In the wider street canyon (H/W = 1), OSDs reduce physiological equivalent temperature (PET) by 9.6 °C and 10.1 °C, and illuminance by 163.6 klux and 190.1 klux at the east-facing and west-facing sides, respectively, but increase PET and illuminance by 3.8 °C and 39.0 klux at the center. In the narrower street canyon (H/W = 2), PET and illuminance decrease by 6.8 °C and 141.9 klux at the east-facing side, 7.4 °C and 144.7 klux at the center, and 7.1 °C and 180.5 klux at the west-facing side, respectively. An effectiveness index is introduced, indicating that OSDs simultaneously improve thermal and visual comfort at both sides for H/W = 1, whereas excessive shading yields a slightly negative effect for H/W = 2. These findings support shading design in subtropical cities and provide reliable validation for numerical simulations.

Publication Date

2026-07-12

Publication Title

Building and Environment

Volume

304

ISSN

0360-1323

Acceptance Date

2026-07-11

Deposit Date

2026-08-04

Embargo Period

2027-07-12

Funding

This study was financially supported by the National Natural Science Foundation of China (No. 42525505, No. 42505078, No. U2442212, and No. 41905005), Guangdong Basic and Applied Basic Research Foundation (No. 2024A1515510024 and No. 2025A1515012936), Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (No. 311020001), Fundamental Research Funds for the Central Universities, Sun Yat-sen University (No. 24xkjc004), and China Meteorological Administration Climate Change Special Project (QBZJ202503).

Keywords

Aspect ratio, Overhanging shading device, Scaled outdoor experiment, Thermal comfort, Visual comfort

This document is currently not available here.

This item is under embargo until 12 July 2027

Share

COinS