22-layer roof greening plan

Quick answer：

A 22-layer roof greening plan typically refers to a design for a roof garden that incorporates multiple layers of vegetation. This design aims to maximize biodiversity, reduce urban heat island effect, and improve air quality. The layers usually include a waterproofing layer, a drainage layer, a root barrier, a growing medium, and various types of plants such as herbs, shrubs, and small trees. These layers contribute to the stability and sustainability of the roof garden.