3. Results
Emphasizing the RLG: grasses vaporize some water (transpiration
through stomata) and with evaporation from wet soil, this
cooling action decreases roof temperature. Consequently, the RLG
can reduce heat transfer from the roof top into the interior space. It
directly reduces the indoor thermal temperature and increases the
energy performance of the building.
A comparisonwas carried out on an experimental set consisting
of roof top gardens with soil depths of 0.10 and 0.20 m and an
exposed roof. Heat transfer calculations were made on the experimental
model and the results are shown in Fig. 5. This comparison
reveals that the soil depth has a great impact on heat transfer
through the roof when compared to the exposed roof. Fig. 5 shows
that heat transfer reduction was 984 W/m2 (59%) when the soil
depth on the roof topwas 0.10mand a greater reduction of 2337 W/
m2 (96%) occurred when the soil depth was 0.20 m. Normally, RH
decreases with increasing ambient temperature, at the same time, it
increases the water evaporation rate from plant and soil. However
solar radiation increases the heat transfer to the building with time.
Loss of heat through radiation and natural convection also play
important role in this context and is beyond the scope of this study.