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.
Indoor cooling is preferred during hot summers but unappreciated in cold winters. With this research, we aimed to clarify the cooling performances of roof greening throughout the year and identify the optimum roof greening coverage for the indoor thermal environment in Chenzhou, a city in China with hot summers and cold winters. The layout of buildings, building materials, and local climate data of Chenzhou were collected. The ENVI-met model was applied as the analytical tool after its accuracy was confirmed by a field experiment. The Kriging model was employed to interpret the annual effects of roof greening. The analytical results revealed that in Chenzhou, roof greening reduced indoor temperatures throughout the year, and the higher the coverage of roof greening, the greater the performance of indoor cooling. Moreover, hot climates enhanced the indoor cooling performances of roof greening. From the view of annual thermal perception, the increase in roof greening coverage reduced the duration of warm perceptions throughout the year and extended the perceptions of slightly warm, slightly cool, and cool. Generally, increased roof greening coverage improved the indoor thermal perception in Chenzhou throughout the year. The ENVI-met + Kriging model, an evaluation method of annual cycles, can be used to evaluate the annual performance of roof greening in terms of indoor thermal environment in other climate zones.
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