Study on Optimal Layout and Design Parameters of Ventilated Roof for Improving Building Roof Thermal Performances

Abstract

The building industry is one of the key industries for implementing energy conservation and carbon reduction in China. Building roof plays a pivotal role among building components due to the most peak heat gain and large roof area. Ventilated roof is a commonly useful energy-saving solution for buildings. The optimal layout and design parameters of a ventilated roof is critical to energy conservation and carbon reduction of building roofs. To find the optimal layout and design parameters of a ventilated roof, the influences of air vents, air inlet and outlet size, air velocity in the air cavity, solar panel, and air deflector on the thermal performance of ventilated roofs has been numerically investigated in this paper by using a new thermal-flow-solar radiation coupling simulation approach. The research results show that a ventilated roof structure with air vents has better thermal performance than the ventilated roof structure without air vents. As air inlet and air outlet size increases, thermal performance of a ventilated roof first increases and then reduces. The air velocity range of air inlet between 1 m/s and 1.5 m/s has the better energy saving effect than the other air velocities of air inlet. The bigger percentage of solar panel area to roof area, the more energy savings of a ventilated roof. Ventilated roof structure with an air deflector has better thermal performance than the ventilated roof structure without an air deflector. The research findings in this paper can provide beneficial suggestions for optimizing design and assessing energy saving effect of ventilated roofs.

Keywords: Ventilated roof, Coupled heat transfer, Air velocity, solar panel, Air deflector