Sustainable and Resilient Engineering for Facade Design under Uncertainty in the Tropics

Traditional facade design practices are mostly based on the designers' intuition or a single performance criterion such as U- and g-values, which only describe a single facade property. However, facade optimal design in an early stage has a significant influence on the final overall building performance in regard to energy consumption, economical cost, CO2 emission, etc. The main challenge is represented by several sources of uncertainty during the life-cycle. In this paper, the goal of finding a sustainable facade design solution is addressed through the reliability framework of sustainable and resilient engineering (SRE), which is used to predict probabilistic performances, whereas the design alternatives are ranked through the multiattribute utility theory. The adopted metric for ranking these alternatives is the generalized expected utility (GEU), which incorporates the expected utility as a particular case. It is recognized that, under limited and incomplete information, decision-makers are risk-averse, which may provide a suboptimal design. Within the GEU, the optimal design under uncertainty is modeled through superquantiles, which allow evaluating the optimal design with respect to frequent events (i.e., service limit states) and extreme events (i.e., ultimate limit state). It is shown that SRE can include traditional design approaches as particular cases. The main features of the proposed framework are demonstrated through an application to a facade design of a hypothetical commercial office in Singapore with three types of facade options. With the output of the simulations through the EnergyPlus software, the alternatives are successfully ranked using SRE and compared with traditional design practices. The case study shows that the proposed methodology has the potential to overcome the limitation of the current design process and to guide the procurement processes in early facade design. Under the growing climate crisis, the environmental impact's relief requirements have motivated the design of sustainable buildings. Traditional facade design practices are mostly based on designers' intuition, personal experience, and provisions of national codes and standards. This approach may be neither efficient nor flexible and can only satisfy the minimum requirements of the projects and national design standards. Actually, it is quite likely to fail in meeting requirements of different involved stakeholders, especially with the reference to sustainable design. In this study, a novel multicriteria early-stage designs of building facades, grounded on a framework of sustainable and resilient engineering, is presented. The comprehensive consideration of the uncertainties within the decision-making process provides interpretability and explainability to the design choices, e.g., the moisture effect on the uncertainty of the thermal conductivity of opaque facade materials. A benchmark case study shows that: (1) sustainable design may sometimes be hardly incorporated by the traditional design approaches; (2) the current practices may give rise to unconservative designs; and (3) the proposed approach is a viable solution for sustainable facade designs.