Abstract
Recently, various sunshading techniques have been developed and applied to windows, since it is well known that their effects on decreasing energy consumption and improving indoor thermal environment during summer season is very high. However, less attention has been paid to sunshading techniques for exterior walls and roofs, although their total area over a building is usually much larger than windows. In this paper, practical heat transfer calculation method has been developed on the purpose of application to the exterior walls and roofs with vented air-layer. The air-layer has been usually attached to exterior side on the walls and roofs of conventional Japanese residential buildings. Although its original function is water vapor exhaustion by natural ventilation, it is also expected to work as a sunshading layer. The developed method includes heat transfer by conduction, convection and radiation, and can evaluate quantitatively the sunshading and insulating effects of various combinations of techniques such as controls of surface solar reflectance, surface emissivity, opening ratio of the air-layer, and thickness of insulation material.
