Study with CSTB: Assessment of the impact of green walls on urban temperatures
Green walls are often hailed for their many benefits, but what about their actual effectiveness in terms of thermal regulation? A study recently carried out by TRACER in collaboration with CSTB provides concrete answers to this question. Here are the results of this in-depth analysis and their implications for the future of urban greening.
Background to the study
In 2022, TRACER joined the RENOPTIM project, led by CSTB, to assess the impact of revegetation on urban heat islands. The aim of this project is to measure how revegetation solutions, such as green walls, can help reduce temperatures in urban environments.
In April 2023, we put this study into practice by installing a green wall on the south gable of a six-storey apartment building in Sens. This wall, fitted with external thermal insulation and an air space, was divided into two distinct parts: one watered regularly and the other left dry. The aim was to compare the effect of vegetation on surface temperature and the immediate environment.
Key results of the study
Substrate temperature
The results show that the green wall has a significant impact on surface temperature:
- Watered substrate: On sunny days, the temperature of the wet substrate can be up to 17°C lower than that of the dry substrate. On average, over the whole summer, the difference is 3.5°C.
Impact on heat islands
The study also highlighted the effect of vegetation on heat islands:
- Air gap: The temperature of the air gap in the wet half-wall is up to 10°C lower than that of the air gap in the dry half-wall during heat peaks. On average, the difference is 2°C over the entire summer season.
Comments and conclusions
Summer Comfort Inside Homes
The results show that the green wall and air gap are cooler when the system is watered. However, the impact inside the dwellings reveals significant nuances. The green wall was installed on a gable already fitted with external thermal insulation. As a result, although our solution helps to cool the building and reduce heat islands, its effect on indoor comfort is less significant. It's crucial to consider the thermal specifics of each home for an accurate assessment.
Overall impact of the Vertiflore solution
The Vertiflore solution has proven its effectiveness in reducing temperatures in urban environments, both on buildings and on heat islands. Nevertheless, to maximize the benefits of the green wall, it is essential to take into account all the thermal factors of each site.
For in-depth details of this study and its implications, we invite you to consult the full article published by Profeel by following this link: https: //programmeprofeel.fr/journal/mur-vegetalise-un-test-in-situ/