This paper presents a mathematical model yielding a simplified representation of the thermal behaviors of ivy-covered walls. The model is integrated with a CFD program to implement simulation. Experimental results have been used to form the boundary conditions of numerical simulations. A series of parametric sensitivity analyses have been carried out for identifying the key factors that affect ivy- coverings’ potential for reduction on cooling load of the buildings. These analyses indicate that ivy- coverings can considerably reduce the heat flux through the external walls that its cover. Three key parameters have been identified as relevant for ivy- covered wall design: green density (d), covering ratio (r), the supporting grid’s geometrical characteristics.