Energy-efficient window retrofit for existing high-rise residential buildings with the consideration of mutual shading

Window is an important element of a building as heat would transfer between the indoor and outdoor environment through the glazing system. Upgrading the glazing system can help minimize the energy consumption through a reduction in solar heat gain in summer or indoor heat loss in winter. On the other hand, the mutual shading caused by surrounding high-rise buildings could affect the energy performance of the glazing systems. In subtropical climatic region, mutual shading could further reduce the solar heat gain. However, in cold climate zone, overshadowing lowers the solar heat gain in winter resulting in greater demand for space heating. To explore the most energy-efficient window systems for different climates, it is imperative to integrate mutual shading with window retrofit measures when evaluating the thermal performance of a building. This study applies a computer-based simulation program known as DesignBuilder to assess the building performance. The energy model is based on a typical high-rise residential building, and 20 possible energy-efficient glazing alternatives were employed in lieu of single clear glass and the related building energy consumption of those 20 glazing systems was carried out using DesignBuilder. Different directions of mutual shading were taken into account when energy simulation was performed. The results show that the optimum window retrofit solution vary with different climatic conditions. Therefore, it is necessary to consider the effect of mutual overshadowing when selecting the most energy-efficient window retrofit measures in different climates.