By Nidhi DhullReviewed by Susha Cheriyedath, M.Sc.Oct 29 2024A recent article published in Energies examined the impact of an innovative modular green wall on energy use and indoor temperature in a residential case study building in Ghent, Belgium. The southwest facade of the building was covered with a particular type of modular green wall with a special substrate and plants that could purify water for reuse in the house.
Study: Exploratory Analysis of a Novel Modular Green Wall’s Impact on Indoor Temperature and Energy Consumption in Residential Buildings: A Case Study from Belgium. Image Credit: An image to remember/Shutterstock.com
Background
Cities worldwide are facing increasingly frequent extreme local climate variations, and the problem of urban heat islands (UHI) is becoming more pronounced. Specifically, Europe is experiencing hotter summers with more heat waves and frequent droughts.
The physiological equivalent temperature reached over 50 °C during the record heat wave of 2019 in the moderate-climate region of Ghent.
More extreme heat stress is expected to occur in the future. Therefore, ensuring the quality of life in urban areas and making the environment more suitable for living, working, and relaxation requires constant improvement in urban green infrastructure. This includes vertical greenery systems, especially in densely built urban areas with no space for new alleys or parks.
Buildings in urban areas can be made climate-resilient by introducing more natural materials, such as green walls and facades, into the urban infrastructure. Accordingly, this study evaluated the performance of a specific modular green wall system experimentally and computationally in Ghent, Belgium.
Methods
The modular green wall system, a total value wall (TVW), had a specific substrate composition (50% lava, 25% organic soil, and 25% biochar) suitable for different plant species (10–25 cm tall) with the primary function of rainwater and wastewater purification.
Its cooling and insulating effects and impact on indoor temperature and energy use reduction during the hottest summer and coldest winter were quantified.
This modular green wall was installed on a single-family house in the Brugse Poort neighborhood of Ghent. Originally, the annual primary energy consumption totaled 31,804.49 kWh or 297.24 kWh/m2. The researched green wall was installed on the southwest-oriented facade of the house and consisted of 40 panels measuring 60×60×10 cm3.
Monitoring equipment was installed on the house next to the green wall. It comprised a reporter for real-time remote monitoring and a weather station with sensors for measuring CO2, precipitation, wind speed, and four different temperatures. The temperature included in the green wall monitoring was that on the wall without greenery (Tref), in front of the green wall (T1), of the substrate (T2), and behind the green wall (T3).
The above parameters were monitored during summer (July 2023 as the hottest summer period) and winter (January 2024 as the coldest period). Additionally, reference climate parameters were taken from the city’s weather station.
Building information modeling (BIM) models of the house were prepared before and after the green wall installation using DesignBuilder software. The experimental data was used to validate this simulation model.
Results and Discussion
During the hottest summer day (8 July 2023), the temperature in front of the green wall was lower by up to 5.3 °C while that behind the wall was lower by up to 4.7 °C. Thus, the green wall could reduce the exterior surface temperature of the wall during the day. Additionally, it could increase the wall surface temperature at night. However, the differences at night were smaller (up to 0.7 °C) than during the day.
During the entire month of July, the daily maximum, minimum, and average temperatures behind the green wall (T3) were considerably less than those in front of it (T1), exhibiting a cooling effect of the green wall. Additionally, installing a green wall prevented significant temperature fluctuations and the instances of high temperatures on the exterior of the building.
On the coldest winter day (10 January 2024), the temperature behind the green wall was higher during the morning and night hours, up to 3.3 °C compared to the reference wall. Alternatively, on a cloudy winter day (2 January 2024), the space behind the green fence had the maximum temperature, up to 0.7 °C higher than the reference wall and 1.0 °C higher than the front side of the wall.
These observations demonstrated the green wall's insulating effects during winter. Moreover, the green wall decreased the energy consumption for heating the house during winter by 6%.
Conclusion
Overall, the researchers comprehensively analyzed the influence of a specific green wall called TVW on the thermal performance of a single-family house in Ghent.
The monitoring results during the summer demonstrated the wall's thermal contribution to avoiding overheating and reducing the cooling load, consequently reducing cooling energy demands.
Thus, implementing green walls on buildings is a suitable passive method in urban areas with fewer green spaces. It helps mitigate the UHI effect and improves buildings' energy performance. Moreover, green walls can reduce indoor temperature, create thermal insulation, and regulate humidity.
Journal Reference
Radujković, M., Versele, A., & Breesch, H. (2024). Exploratory Analysis of a Novel Modular Green Wall’s Impact on Indoor Temperature and Energy Consumption in Residential Buildings: A Case Study from Belgium. Energies, 17(21), 5267. DOI: 10.3390/en17215267, https://www.mdpi.com/1996-1073/17/21/5267
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