Selection of Optimum Radiant Barrier System (RBS) Location in Double Skin Ventilated Roofs

Abstract

Double skin ventilated roof is one of the important passive cooling techniques that aims to reduce solar heat gain through roofs by reducing both the conduction and convection heat transfer from the roof to the ceiling of buildings. On the other hand, radiant barrier system (RBS) is very powerful in blocking the radiation heat transfer between the two skins. In this research, the effect of placing a thin layer of aluminium foil at different locations on the thermal insulation performance of a double skin ventilated roof model is investigated experimentally and the optimum location that transmits less heat flux from the lower skin is specified. The model is made of two parallel inclined galvanized steel plates. Galvanized steel has been used in the roof construction of industrial buildings and storehouses in Iraq. The radiant barrier is applied alternately, on the outer surface of the upper skin, on the inner surface of the upper skin, suspended in the airgap between the skins, and on the inner surface of the lower skin. These cases are considered as Model A, Model B, Model C, and Model D, respectively. It is found that the radiant barrier can block up to 78% of the heat in Model A, 71% in Model B, 94% in Model C, and 91% in Model D as compared with the Basic Model. Since the radiant barrier in both Model C and Model D blocks almost the same amount of heat, the location of the radiant barrier in Model D is chosen as the optimum radiant barrier location because this model is more practical.