Optimising sustainability in building design from a life cycle perspective

Improving sustainability in buildings has become among the top priorities in the construction sector. Reducing energy consumption is essential due to the industry's substantial contribution to global energy use and carbon emissions. At the same time, supporting economic growth remains crucial, highlighting the importance of balancing environmental responsibility with economic development. Therefore, various aspects of sustainability in building design should be considered simultaneously to develop a practical design that is both energy-efficient and economically viable. Additionally, occupant comfort should not be overlooked. These considerations should be addressed during the early design stages, where there is greater flexibility to implement improvements. Despite previous efforts to advance sustainability in the building sector, there are still gaps in achieving this goal. Foremost among these gaps is the absence of a comprehensive and integrated model to evaluate and optimise building performance from a life cycle perspective, focusing on various aspects of building sustainability. The impacts of different design strategies on building energy consumption need to be analysed from a life cycle perspective; otherwise, optimisations can be misleading, potentially shifting energy consumption between the operational and embodied stages. Moreover, the analysis needs to be comprehensive, as improvements in energy consumption could otherwise significantly increase building costs, making the strategies impractical for real-world application and limiting them to only academic research.The primary aim of this research is to improve building sustainability from a life cycle perspective at the early design stage through three key objectives. First, it develops an innovative, comprehensive, and automated model for analysing the life cycle energy consumption of buildings, particularly modulat buildings. Second, it aims to create a novel model for optimising building sustainability at the early design stage by incorporating the environmental, economic, and social dimensions of sustainability. Finally, a post-optimisation sensitivity analysis is conducted to explore different design strategies and their impacts on various optimised designs in greater depth. In the first stage, to achieve an automated and integrated model, a BIM-hesed LCA model is developed using a visual programming language. This model evaluates the energy consumption of modular buildings across all life cycle stages, including material production, transportation, construction, operation, and deconstruction. The goal is to generate an energy report that identifies energy hotspots within modular buildings, enabling designers to make Informed decisions and develop more sustainable design and construction strategies. In the second phase of this research, a BIM-based multi-objective optimisation model is developed to enhance building sustainability during the early design stage. The focus is on passive design strategies, with the objectives being the optimisation of life cycle energy (both embodied and operational energy), life cycle cost (including investment and operational costs), and occupant comfort. The application of the proposed model led to significant reductions across all objectives, with observed decreases of up to 39.04% in operational energy, 38.1% in embodied energy, 73% in occupant discomfort, and 47.62% in life cycle cost. Following the optimisation, a post optimisation sensitivity analysis is conducted to assess the sensitivity of each objective function to the selected design variables. This analysis enables designers to identify which variables have the greatest impact on sustainability, highlighting the flexibility of adjusting those variables without compromising the objectives. The goal of this research is to contribute to advancing building sustainability and support informed decision-making at the early design stage by providing a comprehensive and integrated model, along with a range of design strategies that allow stakeholders to choose the one that best aligns with their priorities.