Experimental investigation on the thermal performance of a vertical greening system with green roof in wet and cold climates during winter

In recent years, a novel vertical greening system has begun to spread worldwide. This system can provide several environmental benefits, such as alleviating urban heat island effects, increasing the number of green sceneries, improving atmospheric quality, relieving urban drainage pressures, and improving building energy efficiency. To evaluate the effect of a vertical greening system on indoor climate and the energy consumption of buildings under wet and cold climatic conditions during winter, 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. Two types of experimental conditions, that is, with and without heating, were investigated. The experimental data were collected from December 2017, to January 2018. Results showed that without heating, the indoor air temperature swing of the room with vertical greening was significantly suppressed, in comparison with that of the reference room. The indoor air temperature of the room with vertical greening was 1-3 degrees C higher than that of the reference room at night. Meanwhile, the air layer temperature was 1-2 degrees C higher than that of the outdoor air throughout the day. Under heating conditions, the average heat flux through the walls of the reference room was 3.1 W/m(2) larger than that of the room with vertical greening. The measured electric energy consumption of the reference room was 1.22 times that of the vertical green room. An energy saving rate of 18% was achieved during the heating experiment owing to the extra thermal insulation provided by the vertical greening system. (C) 2018 Elsevier B.V. All rights reserved.