Evaluation Of Living Wall’s Canopy Shading Effect In Hot And Humid Climate And Model Modification

In recent years,with the increase in urban building density,the ground green space has drastically reduced,and building walls,roofs and other enclosure structures have been developed for planting and cultivation of greenery.Among them,living walls system is a vertical greening method that has emerged in recent years.Many studies have proved that the use of living walls on building surfaces can effectively reduce heat transfer between indoor and outdoor,reduce building energy consumption,and improve surrounding air quality.Due to the unsteady heat transfer caused by its composition,the thermal performance of the living wall system is difficult to accurately estimate.Domestic scholars have established a preliminary numerical model of heat transfer in living walls,and refined the canopy,growing medium,and wind speed effects among them.As one of the important components of the living wall,the plant canopy can significantly reduce the solar radiation incident on the surface of the building,and reduce the transfer of heat flux through a series of effects such as absorption and reflection.However,the various plant parameters that affect this effect and the shading benefits of different plant canopies on solar radiation have not been accurately quantitatively studied.This paper takes the modular living wall as the research object,and takes the interaction between the plant canopy and solar radiation as the starting point.The research focuses on the extinction of the plant canopy on the incident solar radiation and the influence of plant parameters on the shading benefits.Through field investigation,experimental measurement,and theoretical analysis,the influence of vertical wall canopy structure on shading benefit is analyzed.Summarized the selection of plants,structure types,maintenance mechanisms and spatial effects of the existing living walls in Wuhan;measured the structural parameters of various living walls and the extinction of solar radiation,and quantified the shading benefits of different plants;Based on the solar radiation model,make corrections and verify the accuracy and universality of the model with measured data,establish a database of commonly used living wall plants to evaluate the similarities and differences of the shading benefits of the plant canopy under various input parameters(different plant characteristics,seasonal conditions).In order to maximize the calculation accuracy of solar radiation transmission in the simulation of living wall energy consumption,and to provide a certain reference for the selection of living wall plants in the future.The research results show that the shading benefits of different plants are significantly different,and plants have higher shading benefits at noon.Different environmental parameters and canopy structure parameters lead to differences in the shading benefits of the plant canopy.Among them,the leaf area index and the sun’s altitude angle have a greater impact on the shading benefits of the canopy.Use the measured data to verify the optimized model.The root mean square error is between 0.08-0.12,and the adjusted R~2 is between0.657-0.883,which is reduced by 0.02-0.05 and increased by 0.021-0.192 compared to before optimization.The model has higher accuracy.