Green roofs are covered with growing media and vegetation that enable rainfall infiltration and evapotranspiration of stored water. They are particularly cost-effective in dense urban areas where land values are high and on large industrial or office buildings where stormwater management costs are likely to be high. In VO6, users could have two options for designing green roof, including subsurface ponding and surface ponding types. The difference between the two types is water storing in different layers. In surface ponding types, users could set a parameter for a depth of ponding layer, while in subsurface type, a depth would be set in the storage layer. Both types have roof drains to convey storm water to drainage sewer or retaining area. Key features for green roof are shown in the diagram below.

Parameter Name Description Default Value
Surface Area Ponding
DEPTH-AREA CURVE Depth area curve for surface ponding area, depth is defined from the bottom of the ponding layer For subsurface type, users could set 0 for depth
Engineered Soil Layer SOIL
MOISTURE Initial soil moisture content of the engineered soil layer (frac-tion) 0.3
INFILTRATION Rate with which water moves through porous material (m/hour) 0.5
POROSITY Fraction of soil that is made up of spaces (pores) between particles 0.467
Storage Layer
DEPTH Depth of the storage layer (m) 1
POROSITY Fraction of storage layer that is made up of spaces (pores) between particles 0.4