Does Vertical Greening Really Play Such a Big Role in an Indoor Thermal Environment?

Little attention has been paid to indoor cooling compared with the surface cooling of vertical greening. The few studies on the indoor cooling of vertical greening are almost all conducted in a hot climate area with windowless building models, which is suspected to exaggerate the role of vertical greening in an indoor thermal environment. Through two improvements, this paper explored the realistic impact of vertical greening on an indoor thermal environment. First, we built models according to the actual window-to-wall ratio rather than a fictitious model without windows. Second, an annual cycle evaluation, considering both hot summer and cold winter, was used to replace the typical hot day. With the support of Envi-met and Kriging models, the results revealed that the existing research not only exaggerated vertical greening's positive effects on an indoor thermal environment in hot seasons but also ignored its potential harms to thermal perception in cold seasons. These exaggerated results could easily cause the abuse of vertical greening in cities. In actual windowed buildings, the role of vertical greening in indoor temperatures is not always positive, and the positive effect is not as strong as previous studies suggest.