Summertime thermal and energy performance of a double-skin green facade: A case study in Shanghai

Vertical greening system(VGS) for buildings is drawing more and more research, because that it provides passive cooling for both indoors and outdoors without occupying valuable urban land, and thus can be a remedy for the deteriorating thermal environment of today's high density urban areas. This paper reports an investigation on the summertime cooling performance of double-skin green facade (DSGF) of a recently-renovated 5-storey administrative building in a university campus in Shanghai. The results show that, the VGS created a distinctive microclimate in the cavity: air temperature T-a averagely dropped by about 0.4 degrees C in a daily circle, and maximally 5.5 degrees C for the Southern facade; and by 0.2 degrees C in average and 3.3 degrees C maximally for the Northern facade. The mean exterior surface temperature T-s reduction of the Southern facade by the VGS is 1.5 degrees C and maximally similar to 9 degrees C, whereas the mean interior T-s reduction is 1.2 degrees C and maximally 2 degrees C. The corresponding figures of the Northern facade is 0.5 degrees C, 4.2 degrees C, 0.5 degrees C and 1.3 degrees C, respectively. The indoor thermal improvement by the VGS, evaluated by operative temperature (T-op), is 1.1 degrees C averagely and 2.7 degrees C maximally on the South-facing office, and 0.6 degrees C averagely and 1.9 degrees C maximally on the North-facing office. The initial findings suggest clear potential of VGS in thermal comfort improvement and cooling energy saving, further study is needed to evaluate the yearly energy and comfort effects of VGS on radiation, convective and conduction heat transfer and on daylighting through building envelop, for comprehensive energy assessment considering cooling, heating and artificial lighting.