The building and construction sector faces an urgent need to minimize its carbon emissions and solid waste generation. In this context, reuse and recycling emerged as promising strategies to reduce these impacts without significantly increasing costs. However, employing reused and recycled materials introduces additional uncertainty into the overall project, particularly in lifecycle assessments and cost estimates. This challenges decision-making when selecting end-of-life and beyond-life pathways for construction products. Especially because previous studies have not quantitatively assessed this uncertainty, indicating a gap in the body of knowledge. To address these limitations, this research provides a Monte Carlo Simulation-based framework to evaluate the uncertainty in embodied carbon and the cost of salvaged materials and to support probabilistic decision-making. A case study was used to evaluate the implementation of the framework, in which the reuse and recycling of precast concrete panels for a new project were compared with the use of virgin materials. It was found that the Reuse and Recycle scenarios yielded lower mean values than virgin materials; however, they contained higher uncertainty. In particular, the Reuse Scenario had a mean value for embodied carbon of around half that of those in the baseline, but an uncertainty almost three times higher. The probabilistic analysis indicated that the Reuse Scenario had the highest probability of achieving embodied carbon and cost targets, providing savings of 32.84 kgCO2e/m2 and 242.07 $/m2. Beyond the specific results, the main contribution of this research is the uncertainty analysis and decision-support framework, which can be replicated in other projects.

Accessory Dwelling Units (ADUs) have emerged as a widely adopted tool for adding infill housing in U.S. cities, yet most feasibility assessments remain limited to zoning eligibility, whether a given lot is legally permitted to host an ADU. What zoning-only tools cannot show is where regulatory permission translates into practical buildability, and where it does not. This study develops a GIS-based digital twin framework that integrates zoning regulations with environmental constraints, including flood risk, impervious cover limits, tree-protection rules, and drainage conditions, to provide a more complete and spatially explicit picture of parcel-level ADU feasibility. Austin, Texas serves as the case study, given the city’s recent ADU policy reforms under the HOME Initiative and its pronounced spatial variation in environmental conditions across neighborhoods. The results demonstrate that the digital twin substantially narrows the estimate of feasible ADU parcels compared to zoning-only analysis. In East Austin (78702), 39

The last two decades have witnessed an increasing interest in decarbonizing the construction sector. However, existing literature focuses heavily on residential and commercial buildings, with little attention on capital projects such as industrial facilities, energy generation plants, and civil infrastructure. This study aims to capture the current landscape for decarbonizing the delivery of capital projects, assessing current decarbonization drivers, goals, strategies, and challenges. To achieve this objective, the research proposes a mixed-methods approach that obtains insights from industry practitioners through structured surveys and semi-structured interviews. The results indicate a strong commitment in the sector towards reducing its carbon emissions, with 77 % of the organizations reporting some form of decarbonization-related goals, and 90 % implementing at least one action to reduce embodied carbon on projects. The main drivers are concerns about global warming and the implementation of environmental programs within an organization, especially influenced by targets set by project owners. Limitations were also identified, for example, less than 50 % of the organizations developed carbon baselines for their projects and track their decarbonization progress. As indicated by the majority of respondents, relevant decarbonization barriers are the lack of knowledge and the potential cost impacts. A critical factor to overcome these challenges is the alignment between different stakeholders, as well as the support from governments and policies. The findings presented in this research map the current status of the industry, detect the gaps, and identify actions needed to transform current decarbonization objectives into tangible improvements.

Design for reuse (DfR) is a key strategy for advancing sustainable construction, yet its adoption remains limited. A major gap is the lack of tools that incorporate topological assessments to support deconstruction and material reuse planning. Existing quantity takeoff (QTO) tools primarily focus on design and virgin material procurement stages, often overlooking the in-situ topology of materials and the realities of disassembly, resulting in inaccurate reuse estimates. To address this, a method is introduced that topologically evaluates structural components within as-built models, identifies connection types using enriched information, and anticipates component availability after deconstruction. Using the results of two institutional building projects, this framework is shown to more accurately estimate quantities of materials at their end of life, facilitating planning and decision-making for sustainable construction initiatives. The main contribution of this paper is the adaptation of conventional QTO practices to better support circular decision-making at the end-of-life stage of construction projects.

Reuse is not commonly adopted in practice, despite its acknowledged benefits, partly due to the complexity of the design process, considering geometric constraints and fluctuating stock availability. A multi-objective optimization framework for algorithm-based stock assignment and path generation is developed, specifically for onedimensional material systems (e.g., piping, timber, steel), to maximize reuse allowing for serial connections of stocks. Under the overall genetic algorithm-inspired optimization structure, improved A* and heuristic algorithms are used for pathfinding and stock assignment, respectively. A comparative analysis of the fitness values for both lab-based and real-world case studies demonstrates the robustness of the approach with different optimization parameters, stock availability, and scale complexity. This method can help the next users of construction and demolition waste and spare maintenance parts reuse more materials, contributing to a circular economy in the construction industry. Future research can further expand and apply the proposed approach to more complex real-world scenarios.

Reuse of building components, particularly deconstructed equipment (e.g., transformers, pumps, light fixtures, and networking systems), has gained increasing attention due to its environmental and economic benefits. However, a large number of equipment is often land-filled because mapping their next destinations for reuse is complex to perform manually. These processes for mapping are not currently automated or supported by technology. This study aims to assist site managers in understanding the storage assignment process of deconstructed equipment to warehouses, the interim storage for reuse, through an agent-based simulation model to support increasing reuse rates. Simulations are conducted for the equipment inventory of three deconstruction sites to assess the impact of deconstruction schedule distribution, initial storage capacity, and relocation time from a warehouse to the final destination on the final reuse rates. The results demonstrate the necessity of inter-site-level deconstruction schedule coordination, providing decision-makers practical insights to strategically plan reuse in the construction industry.

Every year, buildings around the globe undergo adaptation services to address changing user needs, deterioration of conditions, and code updates, among others. Building obsolescence is inevitable, and when it occurs, a proactive adaptation plan often does not exist, resulting in disruptive, time-consuming, and costly services. New buildings, however, can be designed to be more resilient against obsolescence by leveraging circular economy principles. However, a proper understanding of building obsolescence is crucial since it precedes (and, in fact, elicits) the process of adaptation. This paper utilizes semistructured interviews with 15 industry professionals, including owners and contractors. The interviews explore their perspectives on the causes of building obsolescence, the challenges involved in adapting buildings, and proactive strategies to improve adaptability. Eight recommendation themes on proactively designing buildings to be more resilient against obsolescence are identified, including implementation of robust design, use of modularity, and use of durable structural components. Furthermore, four main challenges are identified in the building adaptation process. The research findings can help planners avoid common issues that impede the building adaptation process.

There is increasing attention toward reducing greenhouse gas emissions on construction projects in light of their significant contribution to global warming. One of the scrutinized aspects is the measurement and reduction of embodied carbon (EC), including the materials and activities involved in the project execution. However, the assessment of this environmental impact generally involves uncertainty due to the lack of precision in emission factors and the inherent unpredictability in prospective project parameters. Since data quality and accuracy for embodied carbon assessments vary significantly across project phases, it is crucial to evaluate how the uncertainty in the results changes when the assessments are performed at different times of the project development. This study presents a new framework using Monte Carlo (MC) simulation to systematically evaluate and compare uncertainty in carbon assessments across project phases. Three case studies are used to validate this framework and statistically model how the uncertainty varies from one phase to the other. The individual assessment of the case studies reveals that the change in uncertainty for different project phases can range up to 20%-31% based on the differences in the coefficient of variation (COV). Similarly, the mean value reported can vary from 6% to 14%. The uncertainty tends to be reduced for later project phases showing confidence intervals for the coefficient of variation of 0.33-0.39, 0.12-0.28, and 0.04-0.20 for concept, engineering, and construction stages, respectively. However, the specific values depend also on the particularities of the project and the data that each project has available. This work demonstrates that an uncertainty analysis should be included with all embodied carbon assessments to increase the transparency of the emissions reported and the comparison of alternatives. By increasing the reliability of assessments, this study supports the reduction of the net contribution of the construction industry to global carbon dioxide emissions.

The construction industry has shown a rising commitment to measure and reduce carbon emissions. Previous research has focused on implementing lifecycle assessments (LCA), a quantitative approach to estimating environmental impacts. In particular, some studies assessed existing standards, databases, and computing tools for carbon accounting. However, none of them have illustrated the interconnection between these elements under different scopes of analysis, such as product, project, or corporate level. This paper presents a framework that depicts the processes, technology, and sources available to measure carbon in the construction sector. The approach employs a systematic literature review to create a matrix that summarizes this information across product, project, and corporate levels. In addition, the relationship between project lifecycle stages and organizational carbon scopes is represented in a conceptual map. By providing this framework, this study contributes to the systematic implementation of carbon measurement in the construction sector, thereby reducing its global carbon emissions.

Design for disassembly (DfD) is a strategy that facilitates material recovery by proactively identifying key elements of a building that can be deconstructed in the future. Many factors influence the success of DfD, including connection type, use of lightweight components, and government policies. Many studies have focused on these factors, and several tools have been proposed to support DfD implementation. To better understand the nature of these factors and tools, this study presents a literature review composed of two parts. The first investigates critical success factors (CSFs) influencing DfD in the construction industry using a people, process, and technology (PPT) methodology. The second part focuses on DfD computer-aided tools, and the state-of-the-art in the development of these tools is discussed, along with their main contributions. In conclusion, 27 DfD critical success factors are identified along with several tools that support its implementation.

Given the urgent need for decarbonization of the construction industry due to its pivotal role in global greenhouse gas emissions, industrialized construction (IC) has emerged as a promising technique to change the productivity, quality, and sustainability of construction. Although some evidence and case studies reveal that IC has distinct decarbonization advantages compared with traditional construction, there still is a need to analyze best practices, opportunities, and challenges in order to guide industry practitioners and to define key knowledge gaps. A systematic review was conducted following the three core steps: database search; research gap identification, analysis according to key lifecycle stages, and decarbonization themes. This synthesized existing academic works at the intersection of industrialized construction and decarbonization to provide a comprehensive understanding of decarbonization in IC. The findings show that although a significant amount of research focused on emissions during project stages A1-A3, there is a noticeable research gap in evaluating the carbon emissions associated with transportation, operations, and end-of-life attributes of IC. Moreover, the absence of real-time assessments during the B6-B7 operational stages impedes optimal carbon emission assessment. The verbosity of carbon estimation and tracking methodologies also adds challenges to ensuring that additional carbon impacts of IC are adequately offset by improved efficiency and lower onsite emissions. The potential of decarbonization of IC can be explored further by future research on the standardization of life-cycle assessments, development of continuous carbon-tracking methodologies, and application of alternative materials and new technologies. The effectiveness of IC practices in reducing carbon emissions may vary, as deduced from the reviewed literature. However, the conscientious selection of materials characterized by low embodied emissions can contribute to a reduction in carbon emissions, applicable to both IC and non-IC projects. IC projects are uniquely positioned to achieve an even greater reduction in carbon emissions because of a unique process that innately offers waste reduction and product quality improvements. Although a considerable volume of research has focused on estimating carbon emissions, there appears to be a gap in tracking the precise quantity of emissions across various life-cycle phases within IC. Although there is considerable research on decarbonization in prefabricated components, research on specific life-cycle phases still is lagging. Furthermore, future research should prioritize investigating similar opportunities for three-dimensional (3D) volumetric systems.

The pursuit of construction projects with error-free design, streamlined manufacture and assembly, and rework-free construction is often dominated by project management best practices. Yet this paradigm can be increasingly supported by cyber-physical systems that include elements such as generative design, laser scanning, computational algorithms, and digital fabrication, thus closing the gap between design and reality. This paper presents a regenerative BIM system that adapts 3D geometry in real time to match field conditions, thus achieving the ability to digitally fabricate to field conditions (i.e., "digital fab-to-field"). Such a system is particularly useful in 2D exterior panelized construction (e.g., curtainwalls and composite metal cladding), which frequently undergo design iterations and onsite rework due to geometric inconsistencies between site interfaces and manufactured components. The proposed framework is demonstrated using a digital mock-up of an exterior cladding assembly, which is shown to adapt to changing site conditions as described by a 3D point cloud.

A core feature of digital twins (DTs) is the dynamic connection between a physical asset (or system) and its representative virtual model. Across the dimensions of various DT architecture types, the geometric dimension is foundational for use on AEC projects. While mechanisms for maintaining a dynamic connection between physical and digital geometry do exist, they tend to involve replacing existing information (e.g., progressive scan-to-BIM processes), rather than dynamically updating pre-existing geometric information. To support the latter vision, this paper presents an automated model updating architecture specifically for geometry by considering shape, pose, and topology parameters. Functional demonstrations are used to illustrate how this framework can be applied to different facets of building construction systems.

Assessing the Viability of Robotic Disassembly of Building Components for Resource Recovery Christopher Rausch, Seungah Suh, Nikiforos Repousis, Nathan Titterington, Han Nguyen Pages 1048-1056 (2024 Proceedings of the 41st ISARC, Lille, France, ISBN 978-0-6458322-1-1, ISSN 2413-5844) Abstract: The transition towards a circular economy will, in large part, necessitate the disassembly and recovery of components from existing building stock. Robotic disassembly has emerged as a technique in other (non-building) industries as a method for efficient and scalable resource recovery. Since robotic disassembly has yet to achieve a similar level of maturity in the building industry, this paper presents an assessment framework towards this aim. This framework harmonizes the demonstrable capabilities of robotic systems (via literature synthesis and currently available hardware) with suitable deconstruction applications (using a case study of a large institutional building). The results yield strategic paths forward for enabling robotic disassembly of building components. Keywords: robotics, circular economy, deconstruction, sustainability, automation, collaborative robot DOI: https://doi.org/10.22260/ISARC2024/0136 Download fulltext Download BibTex Download Endnote (RIS) TeX Import to Mendeley

Verifying geometric compliance in offsite manufacturing (OSM) is key for ensuring adequate fit-up, structural integrity, building system performance, and assembly alignment on site. The use of a geometric digital twin (gDT) from 3 D scanning can be used to digitize an assembly to detect and resolve potential problems in a prescient manner. The contribution of this article is the development of a framework for deploying and comparing three distinct gDT approaches for use during fabrication and assembly in OSM: (1) a scan-vs-BIM approach, (2) a scan-to-BIM approach and (3) a parametric BIM updating approach. Results from a commercial building project show that scan-vs-BIM is the most accurate approach, parametric BIM updating produces the most semantically rich gDT, and scan-to-BIM is a middle-tiered option, striking a balance between representational accuracy and semantic enrichment. This study concludes that future research should develop a hybrid solution of these gDT approaches and additional more accurate measurement technologies for optimal deployment in OSM.

The current era of modular building construction has been largely immutable for the past century in terms of its aspirations, drivers, and objectives. Delivering prompt, cost-effective, and high-quality assets has characterized this era. Yet, a new era is emerging—centered on the post-asset-delivery phase, espoused by prominent circular economy principles. The ability to reconfigure and reuse modular building assemblies in a highly agile manner poses significant opportunities for revolutionizing the environmental and economic impacts of our ever-growing built environment. This paper establishes the groundwork for transitioning toward the next era of modular construction. First, a review of current efforts being made to facilitate this transition is identified. Then, using additional inputs from the industry, a People, Process, Technology (PPT) framework is used to summarize current drivers and constraints. This research provides a cross-sectional analysis of where the modular industry is and how it can transition into its next era.

Dimensional variability of components and assemblies in construction can lead to significant defects, rework, and project risk if not managed effectively. Given the complexity of using tolerance management to control dimensional variability, an automated BIM-based approach is highly propitious, while currently elusive. This paper develops the first iteration of a domain model for tolerance management (ToleranceDM) using two case study examples within the domain of building construction. The results are shown to (1) consolidate the scattered, disparate existing “knowledge” and research on tolerance management into a single standardised, uniform framework, and (2) formalise this knowledge so that it can be unambiguously interpreted and parsed into software systems for automated tolerance management in construction. ToleranceDM functions as a key step towards benchmarking process capabilities, computing tolerance compliance automatically, and enabling in-field communication of tolerance requirements. Future research should explore case studies in different construction domains, along with developing an improved abduction framework and integrating as-built project data for tolerance compliance checking.