Cooling and Energy-Saving Performance of Different Green Wall Design: A Simulation Study of a Block

Abstract

To mitigate the urban heat island (UHI) and release the low carbon potential of green walls, we analyzed the cooling and energy-saving performance of different green wall designs. Envi-met was applied as the main simulation tool, and a pedestrian street named Yuhou Street was selected as the study object. Four designs of walls were summarized and simulated, demonstrating the living wall system (LWS). Super soil had superiority in cooling and energy saving. Outdoor air temperature, indoor air temperature, outside wall surface temperature, and inside wall surface temperature were analyzed. Apart from the outdoor air temperature, the other three temperatures were all significantly affected by the design of green walls. Finally, energy savings in building cavities were determined. The indoor energy saving ratio of the LWS based on super soil reached 19.92%, followed by the LWS based on boxes at 15.37%, and green facades wall at 6.29%. The indoor cooling powers on this typical day showed that the cooling power of the LWS based on super soil was 8267.32 W, followed by the LWS based on boxes at 6381.57 W, and green facades wall at 2610.08 W. The results revealed the difference in cooling and energy-saving performance of different green walls in this typical hot summer area.

Simulating and Comparing Different Vertical Greenery Systems Grouped into Categories Using EnergyPlus

“…The energy exchange on a surface, due to sensible heat flux, is perceived as an increase or decrease in surface temperature. Heat transport occurs through convection, and after a comparison (using the EnergyPlus simulation program) with other studies [37,43,52], the mathematical formula proposed by Stec et al [32] appears as the one that best fits what is stated by FAO [38]: Nu = 0.37 Gr + 6.417 Re 2 0.25 (4) where Nu, Gr and Re are, respectively, the Nusselt, the Grashof and the Reynolds number. Thus, the convective heat transfer coefficient h can be expressed as follows:…”

“…The search for technological systems and materials for urban and building regeneration, especially in recent years, has paid particular attention to sustainability. The integration between vegetation and buildings responds effectively to this request, providing benefits proven by several studies: the reduction of CO 2 emissions and the high temperatures that determine the "heat island" effect, modifying the urban microclimate [1][2][3][4][5], the increase in the quality of life [6,7] and the improvement of building hydrological [8] and thermal performances. Vertical Greenery Systems (VGS), especially, have a great potential, as buildings in urban areas develop mainly vertically, while Green Roofs (GR) only affect the higher floors in tall buildings [9,10].…”

Evaluating the 3D cooling performances of different vegetation combinations in the urban area

“…Many researchers have proposed some effective strategies to combat the UHI effects [10][11][12][13][14][15] and urban greening is proven to be among the most effective ones [16,17]. Vegetation reduces carbon dioxide through carbon sequestration, which leads to a reduction in greenhouse gases (GHG) and thus heat [18].…”

Research on Annual Thermal Environment of Non-Hvac Building Regulated by Window-to-Wall Ratio in a Chinese City (Chenzhou)

“…ENVI-met provides high-resolution modeling of the heat and humidity transfer at the building facade and a prognostic calculation of wall and indoor temperatures. Compared with the other traditional computational fluid dynamic simulation software platforms, ENVI-met realizes the analysis of small scale changes in urban design, such as tree setting and building configuration [28,29], which makes it a widely used analytical tool in the field of the built environment. ENVI-met is also well known among the scientific community for its higher accuracy, with the Pearson value of its predictions being proved as 0.956, exceeding 0.866 (Solweig model) and 0.867 (Rayman model) [30,31].…”