The Simulation of Thermal Processes in Plant Cover on Roofs

Abstract

Many approaches are used in the space cooling of buildings. Based on experiments carried out on the rooftop of a low-rise commercial building in Singapore, a rooftop garden reduced the roof surface temperature by up to 30oC. The ambient air temperature was also reduced by up to 4.2oC. To examine the factors that influence space cooling in buildings, three configurations are investigated. First of all, a bare roof, which comprises a layer of concrete over the indoor air is studied. Next, an unplanted roof is examined. The difference between a bare roof and an unplanted roof is an additional layer of soil. The thickness of the soil layer, the volumetric moisture content of the soil, and the density of the soil are varied to examine their impacts on passive cooling. Lastly, the planted roof is studied. The leaf area index ( ) is varied from 2 to 5 and its effect on the indoor air temperature is evaluated. The three configurations are modeled in programming language C++.From the simulation results, it was found that the thickness of the soil layer, the volumetric moisture content of the soil, and the soil density have minimal effects when they are varied. Nevertheless, the addition of a layer of soil can reduce the room temperature by up to 2 oC. The most important factor is the leaf area index of the plant. With effective shading, the temperature of the room can be reduced by up to 5 oC.