Reducing energy consumption and improving comfort by retrofitting residential buildings in the hot summer and cold winter zone of China

China's Hot Summer and Cold Winter zone with a 550 million population, accounts for 45% of China's building energy consumption; as such, building retrofits could offer substantial energy savings. This paper presents results from a dynamic thermal modelling study of a typical urban multi-storey residential building under three types of A/C operating schedules. Seven energy saving retrofit measures (external wall insulation, roof insulation, double-glazing, air infiltration control, window shading, communal staircase design and energy-efficient A/C) were evaluated, and the retrofit strategy with the highest annual energy savings and lowest thermal discomfort was identified. This retrofit strategy was subsequently evaluated for other flats (apartments) with different orientations and positions in the typical building. The annual space-conditioning energy could be reduced by 59 to 68%, depending on the flat location, orientation, and A/C operating schedule. The findings were then scaled up to estimate the potential energy savings in the city of Chongqing. Over 320 multi-storey residential buildings were represented by twelve archetypes. Space-conditioning energy consumption was reduced by up to 58% (18.8 TWh). This work provides evidence of the potential energy savings of city-scale retrofit that could aid China in reducing building energy consumption and achieving net-zero carbon emissions by 2050.