Optimizing interconnected embodied and operational energy of buildings: An embodied energy factor approach

Abstract

This research explores the pivotal role of buildings in global energy consumption and carbon emissions, emphasizing the necessity for sustainable design practices that prioritize energy efficiency and carbon neutrality. The complexity of reducing the energy and carbon footprints of buildings arises from the interrelationship between operational and embodied energy flows. Optimizing operational energy can inadvertently impact embodied energy, complicating sustainability efforts. To address this challenge, we introduce the embodied energy factor (EE factor), a novel metric that quantifies the embodied energy required to save one unit of operational energy. This metric enables the prioritization of design measures that reduces both operational and embodied energy impacts. Employing a multi-objective genetic algorithm, we optimize two case studies of commercial buildings, utilizing the Energy Plus simulation tool for operational energy assessments and an input-output-based hybrid database for embodied energy calculations. The optimization process evaluates 17 design measures, separately, including building orientation, window-to-wall ratio, and various wall, floor, window and roof construction layers. Results from the San Francisco case study indicate that roofing materials have the lowest EE factor of -47.88. Notably, modifications to roofing result in the greatest total primary energy reduction of 9.45 %. In the Dallas case study, flooring materials with an EE factor of -43.74 rank highest, achieving a maximum total primary energy reduction of 37.36 %. There is a correlation between the EE factor ranking system and reduction in total primary energy use. These findings highlight the critical importance of integrating operational and embodied energy considerations in building design to advance sustainable practices.