Decision-making under uncertainty in the early phase of building facade design based on multi-objective stochastic optimization

In response to the European 2030 climate and energy policy framework and to satisfy various stakeholders, trade-offs between different goals should be considered in the planning phase of a building. In the early phase, uncertainties are inevitable and should be modeled in the decision-making process. Especially for early modeling using building information modeling tools, it is of interest to find out appropriate "placeholder"materials. In this paper, we proposed a multi-objective stochastic optimization (MOSO) framework for decision -making in the early design phase of building facade design under uncertainty. Herein, two types of uncertainty were included: uncertainty in design decisions and environmental uncertainty. Coupled with a multi-criteria decision-making (MCDM) strategy, the framework aims to narrow down the possibilities of the material choice and to provide possibly robust solutions. Categorical and continuous parameters were considered to achieve three objectives: life cycle assessment in form of global warming potential, life cycle cost and thermal transmittance. Through a case study with solid timber and brick construction types, the proposed framework was validated. Results show that the insulation and outer wall cladding are the most varying parameters of the Pareto-optimal solutions for building facade design. In general, an environmental advantage in solid timber construction and an economic advantage in solid brick construction can be seen. With the established framework, decision-making considering dynamic changes during the planning process can be potentially realized in future works.