A holistic design approach for residential net-zero energy buildings: A case study in Singapore

The concept of net-zero energy buildings is an important element and dimension of the sustainable built environment. This paper introduces a holistic design approach for residential net-zero energy building (NZEB) by adopting the Triple Bottom Line (TBL) principles: social, environmental, and financial. The social need is mapped to human comfort and nature contact (i.e. thermal comfort achieved by natural cooling, and visual comfort achieved by daylighting); the environmental need is mapped to energy efficiency; and the financial need is mapped to life cycle cost (LCC). Multi-objective optimizations are conducted in two phases: the first phase optimizes the utilization rate of natural cooling and daylighting, and the second phase optimizes energy efficiency and LCC. Sensitivity analysis is conducted to identify the most influential variables in the optimization process. The approach is applied to the design of residential NZEBs in a tropical country, Singapore. The potential of building residential NZEBs in Singapore is evaluated with two typical residential building types: a landed house and apartment building. The required capacity of a renewable energy system (RES) is calculated. Results show that while it is achievable to build a net-zero energy landed house with only rooftop solar panels, it is much more difficult to achieve net-zero energy for apartment buildings. Further design considerations and analysis show that for a 25-floor H-shaped residential building with a solar panel integrated facade, the produced electricity is able to meet the energy demand of up to 19 floors. Findings and derived insights from the case study show that although some variables need to be carefully selected to balance daylighting and natural cooling, the two objectives do not always contradict each other regarding certain variables. Similarly, environmental aims and economic aims do not always contradict each other on certain variables. Also, the social aims do not contradict environmental and economic aims, as the findings show that designing for daylighting and natural cooling contributes to the improvement of energy efficiency and cost effectiveness. These results provide a framework and modeled cases for design insights, parametric design, and trade-off analysis toward sustainable and livable built structures.