Experimental Research about Solar Radiation Shielding by a Natural Vegetation Recycling Material (Reed Screen)

Abstract

The heat island phenomenon, whereby the temperature of urban areas comes to be high in the shape of an island compared with the suburbs, is said to be one of the modern issues of urban environmental problems. It has been thought that the main causes of the urban heat island phenomenon are an excess of heat energy in urban areas, such as an increase in the urban population accompanying the development of rapid economic activity, an increase in artificial buildings, a reduction in green tracts of land, and an increase of greenhouse gas. Although heat island solution techniques, such as green roofs, green walls and heat shield coating with high reflectiveness, have been studied and put into practical use, there are still problems to be solved with these techniques, such as reducing the cost of execution and maintenance. As one solution to these problems, the use of as a heat shield material has been considered. The used as a raw material for have important functions in connection with the conservation of nature, such as the effectiveness whereby they absorb nutrient salts, the prevention of eutrophication, the formation of nursery grounds for aquatic life forms, and the absorption and fixation of carbon dioxide. Periodical harvesting is required for reeds to maintain these functions. However, since there is little practical usage after harvesting, sufficient harvesting is not performed. Therefore, a very important subject has been to consider how reeds can be utilized after being cut. Accordingly, if reed screens are utilized as heat shielding and heat insulation materials on the roofs of buildings, the practical use of the reeds after harvesting will be greatly promoted. The purpose of this research is to show how a new circulation system using can be built as a solution for the urban heat island phenomenon which reduces cost and becomes maintenance-free. In this paper, the solar radiation shielding effectiveness in the daytime in summer and the heat insulation effect at night in winter were checked in a survey whereby screens, a natural vegetation recycled material, were installed on the rooftop concrete surface of a building. Furthermore, the paper shows the result of collecting basic data on heat island mitigation effects in sensible heat flux and upward long-wavelength radiation, which influence the space outside a building.