When
the CR exceeded 80%, the slope of the TRR against the TLT was
shallow, and when the CR was under 80%, the slope of the TRR
against the TLT was high. N.H. Wong et al. [6] found the maximum
temperature decrease caused by plants was around 30 C,
depending on the density LAI of the plants. They also found that
wet soil can provide an insulating effect for the whole day, while
vegetation mainly provides sun protection during the daytime. H.F.
Castleton et al. [11] found that green roofs can significantly reduce
energy use in buildings with poor insulation values, both in
summer cooling and winter heating. The moisture content of the
soil affects the extent of heat lost through evaporation. With
regard to wet soil, heat has been shown to be drawn out of
a building where the transpiration effects are high. The conductivity
of the soil also increases with moisture content, meaning
dryer soil conditions offer better thermal insulation. A. Niachou
et al. [12] found that the heat transfer within surfaces that are not
covered with green roofing is greater than in surfaces covered with
green roofing; the estimated differences of the heat transfer
coefficients varied from 6 to 16 W/m2. S. Onmura et al. [13] studied
the evaporative cooling effect of RLG and found that the evaporative
cooling effect from a RLG plays an important role in
reducing heat flux. From their field measurements, they found the
temperature of the roof slab decreased from about 60 to 30 C. S.
Wanphen and K. Nakano [14] found that water content, solar
absorption and wind, all have significant influences on cooling the
surface temperature