Life-cycle assessment of Water-filled Glass (WFG)

Energy properties of building envelopes play a major role in the carbon footprint of the built environment, which is responsible for about 40% of the anthropogenic greenhouse gas (GHG) emissions. The impact of building envelope is twofold: firstly, better insulation (U-Value) leads to a reduction of energy demand, secondly, the envelope itself is responsible for a significant share of the overall embodied energy of a building. The two energies are often in inverse relationship, e.g. lowering operational energy with more insulation or Building Integrated PV (BIPV) also increases embodied impact. While it can be argued that the operational energy has higher proportion in the life cycle of a building which justifies such investment, one should also recognize that climate goals are becoming more ambitious and have shorter time scales than lifespan of a building (e.g. climate goals for 2030). In light of these developments, it can be argued that there is an increasing demand for energy-efficient facade technologies that can lower operational energy consumption compared to standard glass with low impact on embodied energy. This paper presents a whole life-cycle assessment (LCA) for water-filled glass (WFG) technology. WFG is a hybrid transparent facade construction that utilizes a water infill for reducing energy demand (47-72% compared to double glazing (M. Gutai & Kheybari 2020)) and improving thermal comfort. This innovation presents a unique approach compared to other glazing systems because the operational energy reduction of WFG is achieved by an added water infill, which has minimal embodied energy requirement. The significance of this evaluation is that a comprehensive LCA of WFG for an office is presented here for the first time. The paper evaluates the use of WFG in a theoretical project in two climates and compares it with existing standard glass options. Additionally, as a novel approach, the paper introduces the benefit of WFG as a hybrid glass facade where fluid medium is combined with a solid structure to build on the advantages of both. This new facade design approach can represent a sustainable strategy to improve the overall environmental impact of new and existing buildings and offer a new paradigm in facade design where glass envelope becomes an asset for environmental impact instead of being a liability.