Experiment Investigation On The Energy-saving Of The Building With Vertical Greening System In Hot-summer And Cold-winter Zones

Over the past few decades,because of the rapid urbanization in China,a large amount of natural vegetation area was replaced by concrete construction.This action has caused severe environmental problems,such as urban heat islands,low atmospheric air quality,and high energy consumption.Apart from the large energy consumption of buildings,shrinking urban green space is also a problem caused by the urbanization process.Green spaces have a great influence on the urban microclimate,and urban vegetation can help mitigate the heat island effect by increasing the reflection of solar radiation,reducing energy storage in solid surfaces,and cooling the air directly via evapotranspirationTherefore,reducing building energy consumption and increasing urban vegetation areas are urgently necessary for the sustainable development of China.In recent years,vertical greening,which is a new type of greening system,has begun to spread worldwide.It fully uses building’s structural surfaces,such as facades,balconies,columns,and roofs,to grow green plants.As a new type of greening method,vertical greening can not only address the current problems of shrinking green space,poor air quality,and city heat islands,but it can also relieve urban drainage pressures and improve the overall energy consumption of buildings.To evaluate the effect of a vertical greening system on indoor climate and the energy consumption of buildings under wet and cold climatic conditions,contrastive experiments were performed in this study.Two experimental rooms of equal size with the same wall structures were set up in Hunan Province,China.One room had a vertical greening system,whereas the other room did not have one and was used as the reference room.In the experiment during winter,the results showed that without heating,the indoor air temperature swing of the room with vertical greening was significantly suppressed,and the value was 1-3°C higher than that of the reference room.Under heating conditions,the average heat flux through the walls of the reference room was 3.1W/m~2 larger than that of the room with vertical greening.The measured electric energy consumption of the reference room was 1.22times that of the vertical green room.And an energy saving rate of 18%was achieved during the heating experiment.In the experiment during summer,the results showed that under cooling conditions,the indoor black-globe temperature of vertical green room was 0.55-2°C lower than that of the reference room during the experiment time.Meanwhile,the average heat flux through the walls of the reference room was 4.15W/m~2 larger than that of the room with vertical greening.The measured electric consumption of the reference room was 1.32 times that of the vertical green room.And an energy saving rate of 24.56%was achieved during the experiment.In addition,the thermal performance of vertical greening system has been analized in this study.The results showed that under the same solar radiation,the envelop surface temperature of vertical green room was significantly lower that of reference room,with a difference 11.7-15.2°C.Under the same conditions with cooling,the operative temperature of the reference room was 0.66-1.7°C W/m~2 larger than that of the room with vertical greening.