Investigating the effect of green walls on the surrounding microclimate in the autumn season during hot semi-arid climate of Shiraz

Document Type : Original Article

Authors

1 PhD Candidate in Architecture, School of Architecture and Environmental Design, Iran University of Science and Technology, Tehran, Iran

2 Professor, School of Architecture and Environmental Design, Iran University of Science and Technology, Tehran, Iran

3 Associate Professor, School of Architecture and Environmental Design, Iran University of Science and Technology, Tehran, Iran

4 Professor, Faculty of Architecture and Urban Planning, Shahid Beheshti University, Tehran, Iran

Abstract

In recent years, the use of green walls has rapidly expanded across various climates worldwide, becoming a significant strategy for improving environmental quality in both indoor and outdoor spaces. This study provides an accurate evaluation of the impact of green walls on environmental parameters and thermal indices at a real scale. While numerous studies have examined the cooling and heating effects of green walls during the summer and winter seasons, fewer have focused on their effects during autumn. Addressing this research gap, this study analyzes the influence of green walls on the surrounding microclimate during the autumn season at different distances from the walls. The green wall and control wall were oriented to the south-southeast, and given the geographical location and the hot semi-arid climate of Shiraz, this façade is exposed to direct sunlight throughout the day, especially during midday hours. In the autumn season, with the reduction in solar radiation intensity compared to summer, the walls remain exposed to direct sunlight and still have significant impacts on surface temperatures and the surrounding environment. These conditions align with the research objectives, which aim to examine the effect of the green wall, exposed to sunlight, on the surrounding microclimate. Field measurements were conducted over 10 consecutive days on a 24-hour basis at various distances from both the green wall and a control bare wall (without vegetation) during autumn. Indices related to thermal sensation (heat index, humidity index, and summer heat sensation index) and thermal stress (lethal heat stress index) were calculated using the Python programming language. The results showed that, on average, the green wall had the greatest impact at a distance of 0.5 meters, reducing thermal indices by up to 2.1°C. By analyzing the findings from the calculation of thermal indices during peak sunlight hours (11 AM to 5 PM), it was determined that the green wall reduces the heat index by an average of 3.1°C, 2.7°C, and 1.9°C at distances of 0, 0.5, and 1 meter from the wall, respectively. Additionally, the humidex index was reduced by 3.9°C, 3.7°C, and 2.3°C at the same distances. Similarly, during peak sunlight hours, the green wall decreased the lethal heat stress index by an average of 1.6°C, 1.5°C, and 0.8°C, and the summer heat sensation index by 3.5°C, 3.4°C, and 2.2°C at distances of 0, 0.5, and 1 meter from the wall. The data obtained from the non-irrigated days of the green wall demonstrated a significant reduction in the wall's effectiveness. This highlights the critical need for an irrigation system and a regular maintenance schedule to sustain the natural processes of the vegetation and ensure the optimal performance of the green wall. Overall, the findings suggest that green walls can significantly improve the surrounding microclimate during the autumn season, particularly during peak radiation hours, in urban environments located in hot semi-arid climates, contributing to an enhanced quality of life in these areas.

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References

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Journal of Architecture and Urban Planning
Volume 17, Issue 47
July 2025
Pages 28-48

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