Evaluating energy savings retrofits for residential buildings in China

Building retrofit plays an important role in reducing energy consumption and carbon dioxide emissions whilst increasing occupant thermal comfort. This study used DesignBuilder to predict the energy saved by retrofitting a typical flat in Chongqing, a city in the hot summer, cold winter region of China. To increase the reliability of predictions, the model was verified by measured indoor air temperature for a one-week period in April. Five retrofit measures were evaluated, external wall insulation, new windows, increased air tightness, external shading, and higher efficiency of air conditioning. Three types of households with different AC operating schedule were assumed, high, medium and low. The variance in the model predictions due to the uncertainty in the model input parameters was calculated. The results showed that the energy saved depended on the use that was made of the AC system. For high energy users, 40 to 68% of the annual space-conditioning energy could be saved depending on the retrofit, whereas for low energy users the savings were 30 to 58%. Thermal comfort has improved in winter for low and medium energy users, but no improvement in summer.