Optimization of building façade from a life cycle perspective: an integration of BIM-enabled LCA and energy simulation tool
Creators: name: TUSHAR, Quddus
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 330299
subject: Building not elsewhere classified
classificationCode: 400599
subject: Civil engineering not elsewhere classified

description: Understanding the critical design factors assists in identifying the right policies that will reduce energy consumption at the operation and embodied phases, direct and indirect emissions, and ensure a continuous supply of secured energy at a consistent price for consumers during the transition period. The most extensive sort of indirect emissions comes from energy consumption at the operational phase. These indirect emissions include different stages of upstream emissions from fossil fuel extraction, production, and the subsequent downstream emissions generated from transporting the product to consumers. Heating-cooling (H/C) is a crucial source of energy consumption in residential buildings at the operational stage. An increased level of insulation improves R-values in the building façade, offers year-round thermal comfort, in turn, reduces energy bills and emissions for H/C.  However, none of the previous studies attempt to review the optimum energy consumption of a selected house due to H/C at different national code standardized R -values. The investigation critically evaluates the variation of electricity cost, GHG emissions, and selection of the optimized thermostat settings for energy savings in different climatic regions and seasons of a year. An optimized level of insulation at the operational stage has been emphasized in this study, considering the exhaustive sensitivity analysis of the building façade.

The application of passive design strategies for building façade such as orientation, shading, sealing, glazing, and insulation can significantly reduce the necessity of an artificial H/C system, which accounts for 40% of total energy usage in residential buildings. However, none of the previous studies have quantified the energy reduction and their environmental impacts simultaneously for these passive design parameters to achieve the national standard requirements for house energy star rating. Therefore, @RISK optimizer has been performed to optimize operational energy complying with the star rating system by incorporating design strategies. Obtained sensitivity indices show the ceiling (0.84-0.96) and the wall (0.22-0.37) are the most influential predictors for passive design strategies to reduce energy consumption. Comparative analysis of façade insulation performance identifies that 95% of total operational energy consumption of the ceiling can be minimized by using R3 rather than R6 of the national thermal code. Ninety percent energy minimization is obtained in the wall using R2 rather than R4 of the thermal code.

The selection of suitable materials for building the façade is the next step that will not adversely affect the non-renewable source, ecological and human health. However, maximum products create a net-negative impact on the natural environment. Therefore, choosing a suitable material considering the environmental impacts of all phases of the life cycle assessment (LCA) is necessary. An upstream phase of the life cycle consists of materials extraction, manufacturing, the use or operational phase, and finally, the downstream of disposal, reuse, or recycle. Building Information modeling (BIM) has been used in this study as a platform of LCA for interconnectivity between optimized operational energy of @RISK optimizer and consequent embodied phases. Hence, this study focuses on using BIM-Autodesk Revit, energy rating tool (FirstRate5), and BIM-enabled life cycle assessment (LCA-Tally) to quantify, compare, and improve the building design options to reduce carbon footprint and energy consumptions in residential dwellings. The LCA study reveals a significant amount of energy variation, about a 76% reduction at its operational stage.

A significant amount of undesired heat gain and loss up to 87% in summer, and 40% in winter, respectively, are possible through the windows. However, the provisions of the window depend upon several interactive factors such as climatic variation, building orientation, and size, the thermal resistance of façade (R), window to wall ratio (WWR) along with thermal properties (e.g., thermal conductivity (Uw-value) and solar heat gain coefficient (SHGC)) of the windows system. The optimization scheme for glazing selection has been presented by replacing the walls with various windows and proposing a suitable glazing strategy in the national construction code. Energy rating software FirstRate5 has been used to perform thermal simulation over a series of window systems across a broad climatic diversity. Energy simulation suggests keeping the window to wall ratios small, perform better for thermal efficiency. However, providing a zero window is not an optimum solution for permitting daylight and fresh air. The study conducts Multiple linear regression analysis (MLRA) and Monte Carlo simulations to develop energy consumption equations for different glazing options and climates as a function of building orientation, Uw-value, SHGC, WWR, and solar aperture (WWR*SHGC). The benefit-cost analysis of life cycle costing (LCC) specifies the provision of WWR up to 68 % is feasible for optimum trade-offs. Comparative analysis of different framed windows shows the overall suitability of using uPVC windows over others due to less cost, thermal efficiency, fewer impacts on the environment, recycling possessions, and less energy demand at the manufacturing stage.

There is a lack of comprehensive life cycle assessment (LCA) or case studies addressing the potential benefit of precast concrete over conventional structure in terms of thermal efficiency, environmental impacts, flexibility in shape, and integration of waste materials (fly ash). However, the initial embodied energy of concrete is high, and it can be amortized over its extended life span (up to 100 years) by careful detailing and design of precast concrete.  Therefore, the research develops statistical thermal performance models for the precast sandwich panel, precast concrete, and traditional brick veneer construction as insulation (R) and windows to wall ratio (WWR) using energy-simulated data FirstRate5 for different temperate zones. Moreover, conducted BIM-enabled LCA (Tally) investigates the relative impacts of improving concrete panels by incorporating fly ash, increasing compressive strength, changing reinforcement and insulation constituents. The analysis results for lining insulation prefer the broader aspect of extruded polystyrene (XPS) and expanded polystyrene (EPS) boards for their relative weight, thickness, and environmental impacts. Replacement of Ordinary Portland Cement (OPC) with supplementary cementitious materials (SCMs) such as fly ash and slag can reduce structural concrete's emission and energy consumption. Broader technical features, complete sustainability of designed mix concrete incorporating SCMs have not been considered yet. Comprehensive life cycle impact assessment (LCIA) categorizes the impacts in terms of human health (DALY), ecosystem damage (species.yr), and resource availability ($) from the short-term (Individualist) to extended-term (Egalitarian) perspectives. A three-dimensional (3D) graphical representation is projected to combine all the factors into a single value impact.
In conclusion, comprehensive analysis can be successfully used as a meaningful strategy for designers and energy assessors to optimize both operations and embodied energy of building façade in energy efficiency, cost, and environmental sustainability. The energy-efficient design of houses has been validated and justified in the platform of BIM-based optimization techniques. Additionally, developed energy models and conducted LCA will assist in understanding the potential benefit of adopting an insulated precast or sandwich panel with fly ash mix in the construction sector. Even sustainability aspects of the cast-in-place concrete mix can be improved without compromising concrete strength by incorporating a suitable percentage of supplementary cementitious materials (SCMs) such as fly ash or slag.