Investigation on the thermal performance of different lightweight roofing structures and its effect on space cooling load

The lightweight aluminum standing seam roofing system (LASRS) has been widely used as a building element in the construction of either commercial or governmental buildings, and has been proven to be an economic roofing system. However, little research has been conducted into its thermal performance and the effect of the absorptivity (colour) of its external surface on space cooling load in the hot humid area. This paper aims to investigate the thermal performance of the LASRS. A dynamic model is introduced for analyzing the transient heat transfer through the roofs, which was solved by the control volume finite-difference method employing an explicit scheme and validated by measured data. The simulation results show that the heat flux through the roofing system with a polyurethane insulation layer is smaller than that through the lightweight roof with glasswool insulation R1. The space cooling load reduction ratio for light painted envelop could reach about 9.3% compared with black painted one. The cooling load reduction ratio ranges from 1.3% to 9.3% for the roof structure R1 with various surface colour. Therefore, the space cooling load for air conditioning of the building can be considerably reduced (up to 20%) by employing a lightweight roof using polyurethane insulation with white painted surface colour.