In the summer of 2004, an experiment was conducted to assess the moderating effect associated with the planting of green plants on rooftops on the thermal environment of the rooms below. Comparisons were made using different plant types and a variety of associated thermal affects were compared. Temperatures were measured at several points in the vertical on the roof surface material, within the roofing material measurements were made in different types of structural members, within the ceiling, and just below the ceiling in the rooms below. Separate measurements were also made in zones created by arranging the plants in different configurations. Zones were compared by varying the amount of irrigation water and vegetation cover; zones covered by greenery were compared with zones of exposed roof surface. Temperatures were measured from August 16 to September 15. The results showed that, on the hottest day of summer day on record in Yokohama Japan, August 20, temperatures in the zones covered by greenery were moderated by 1 to 4°C in the vertical direction when compared to areas of exposed roof surface. The ground, or roofing, acted to cool the atmosphere for 249 hours in the exposed zones, and for 287 to 449 hours in the zones covered by vegetation. Furthermore, a temperature difference of 10°C in diurnal and nocturnal temperatures was observed between areas that were covered by vegetation and those that were exposed.
