An Example of Utilization of Water Retentive Ceramic Tile for Control of Summer Heat

Abstract

To control summer heat and heat islands in urban areas, we have studied a special ceramic tile which can hold water and evaporate water continuously. We used water retentive ceramic tiles as roof material of shade structures (bams without walls) and analyzed their effects on decreasing heat radiation by both measuring environmental elements and asking to goats in the open field experiments on hot summer days. For a control plot, we used corrugated tin roof which is used traditionally by farmers. On a fair day in July, the highest roof surface temperature of wet ceramic tile was 31.6℃, although that of corrugated tin was 58.2℃. The temperature difference between the wet ceramic tile and corrugated tin was 26.6℃ at maximum, and the values changed from high to low as solar radiation became weak. The temperature difference was brought by the start of evaporative cooling in the wet ceramic tile. The evaporation rate was 0.6 mm/hr at that time. Both roofs provided the same shadow on the ground, but the difference in surface temperature brought a big difference in heat radiation. As wild animals act on instinct, we attempted to determine the reaction of goats experiencing the environment produced by roof shade under strong radiation. They showed a clear reaction only 3 minutes after our departing from the shade. Tokara goats began to stay sitting or standing under each roof of 3m x 2m, three in the wet ceramic tile shade and one in the corrugated tin shade. This situation continued more than 30 minutes under strong sunshine. Goats which stayed under the ceramic tiles could radiate heat of their bodies to wet roof even in summer daytime and they could detect differences in heat radiation from each roof. Physiological response to an environment improved by wet (water retentive) ceramic tiles were proven by animal behavior.