Heat and mass transfer in green roof is expressed by the complex
system of coupled nonlinear differential equations. In this
study the green roof system consists of 4 elements; air, plant, soil
and roof structure. In each one of the elements of the system, equations
of heat and mass transfer are solved according to relevance
among them. Boundary conditions are determined to match the
physics of the problem and to guarantee the conservation of heat
and mass fluxes. There are some assumptions for following equations
which are: