Multi-objective approach to the optimization of shape and envelope in building energy design

In accordance with national and international regulations, the energy usage and emissions of buildings need to be reduced. Both new constructions and retrofit actions should consider the strict requirements of a more sustainable built environment. In many cases, passive and active strategies are only added to the project after an initial conceptual design of the building has already been drawn up, thus limiting their effective integration into the construction as well as their efficacy. Moreover, the complexity linked to different and often contrasting objectives calls for a multi-objective optimization of the process that simultaneously considers energy and emissions in addition to costs. Given the above-mentioned challenges, we propose a novel approach to the multi-objective optimization of new buildings and retrofit actions that considers geometry and envelopes variables, allowing for architectural variability. We demonstrate the efficacy of the proposed method by means of its application to a case study building that is located in the Mediterranean climate and is already compliant with current regulations. The proposed multi-objective optimization approach, based on a genetic algorithm and conducted by means of open access software, made it possible to save 60% of the annual energy demand by means of geometry optimization and, once the geometry was fixed, 23% of the annual energy cost by means of passive and active strategies, while reducing the energy simulations required from 3 × 1012 to less than 8000.