Evaluating the Sustainability of Green Building Systems: LCA, Energy, and Pollution Adsorption Performance with a Multi-Criteria Decision-Making Approach

It has been proposed that green spaces be integrated into the building design as a sustainable solution to the adverse effects of urbanization. Therefore, the sustainability performance of green systems should be evaluated. The current study aims to analyze and compare the life cycle impacts of green systems, including green roof, living wall, and green façade during the operation phase from cradle-to-gate through energy analysis, life cycle assessment (LCA), and pollutant adsorption to find the most sustainable alternatives. Environmental life cycle impact assessments for the different systems were studied via cumulative energy demand (CED), the ReCiPe method, greenhouse gas (GHG) emissions, and energy consumption during the operational phase by simulated buildings. Besides, pollutant adsorption by plants in such systems is assessed. The LCA results indicated that the green facade performed better than other systems through the construction and operation phases. ReCiPe analysis indicated that vermiculite, the cement mortar insulation layer, and irrigation pipes had the highest environmental impacts, while irrigation was also one of the most influencing factors on the life cycle performance. The GHG emissions for the green roof system were notably higher (20,399 kg CO₂) compared to the living wall (15,570 kg CO₂) and the green façade (10,528 kg CO₂). Energy consumption analysis revealed that all these systems reduced energy consumption compared to a conventional building: the building with a green roof showed a 56% reduction, while the green façade and living wall resulted in 25% and 24% reductions, respectively. Furthermore, the plants' performance for pollutant adsorption was analyzed, focusing on Sedum and Hedera . The performances showed that the Sedum used in the green roof was better in adsorbing PM and CO₂. Finally, Hierarchical Adaptive Weighting (HAW) as a multi-criteria decision-making (MCDM) tool was applied to integrate environmental and energy criteria. Accordingly, the green roof option is the best sustainable option for a building. MCDM, however, suggests that the final choice relies upon the policymaker’s approach.