Energy-efficient design protocol for sustainable pitched roof modification from flat roof

Modification of a pitched roof from a flat roof transforms the flat roofs of multi-storey buildings into pitched roofs to improve the building function and landscape effect, provided that the building structures and the foundation bearing capacity meet the requirements; it normally improves the thermal insulation performance of the top layer and solves problems such as leakage of the top layer. This study developed an optimal efficient design protocol for pitched roof modification from a flat roof through comparative analysis. The case study was conducted in an existing building in Hangzhou city, China. In the process of energy consumption simulation on pitched roof modification from a flat roof, control variables were used to keep the building materials, building environments and meteorological conditions consistent. The indoor environment of the building top floor with different gradient settings was simulated in groups, and the hourly temperature, monthly heat gains and losses, and energy consumption of each model were analysed. The results showed a consistent trend in building energy performance of the different models. With an increase in the slope gradient, the building energy performance is higher. This study provides an important reference for modification of pitched roofs from flat roofs in future in terms of building energy efficiency.