4. Discussion
The comparisons of heat transfer and energy consumption
shows that soil and grass greatly reduces the amount of heat
transfer. The effectiveness of a lawn in reducing heat gain depends
on its biological functions (photosynthesis) and the evaporative
cooling effects caused by the moisture content in the soil. In this
study the roof temperature was reduced by evaporative cooling
of the RLG (Fig. 8). S. Wanphen and K. Nakano [14] studied the performance of porous materials to moderate the roof surface
temperature by its evaporative cooling effect and found that
temperature, relative humidity and solar radiation affect the
evaporation. Large particles cause much better evaporation than
small particles. The evaporative rate affects the surface temperature.
The effect of thermal mass can greatly reduce the heat transfer
compared to concrete slabs. The effect of different grass types was
obvious in that savanna grass can reduce heat gain more effectively
than manila grass.