Study on the cool roof effect of Japanese traditional tiled roof: Numerical analysis of solar reflectance of unevenness tiled surface and heat budget of typical tiled roof system

To assess the effect of uneven tiled surfaces on solar reflectance, a numerical calculation was utilized to estimate the solar reflectance of several kinds of surface shapes. In addition, the relationship between solar reflectance of uneven surfaces and surface shapes was analyzed. Drawing on the calculation results, the reduction of solar reflectance from the flat surface was also estimated. A heat budget model of the tile surface and sectional direction of the roof system was developed on the basis of observation results relating to the thermal characteristics of a traditional tiled roof system. A comparative simulation with other urban heat island mitigation technologies, such as green roofs, was carried out under typical weather conditions.

► The roofs of most detached houses in Japan are covered with tiles.
► For the estimating the effect of the unevenness of the tiled surface to solar reflectance, numerical calculation is carried out on several kinds of surface shapes.
► Heat budget model of tile surface and sectional direction of the roof system is built up, and the influences to urban heat island and the heat load for the indoor thermal environment are estimated.
► The tiled roof system contributes to the nocturnal heat island mitigation.