This is generally achieved
by mixing materials of different characteristics at
defined ratios. In the present study, five components (perlite,
vermiculite, sand, crushed brick and coco-peat) were used to
prepare a practical green roof substrate. Table 1 lists physical
and chemical properties of different examined substrate
components. As indicated in Table 1 that substrate components
were of different sizes, which was intentional to alter
the volume of air and water held by the final green roof substrate.
Among the inorganic materials tested, perlite recorded
highest AFP with low bulk density and hydraulic conductivity.
Perlite is a glassy volcanic rock with a rhyolitic composition,
recently has become an important soilless growth medium
and also widely used in potting mixes. It provides good aeration
and optimum moisture retention for superior plant
growth (Gu¨ l et al., 2005).