An Integrated Building Information Modeling and Life-Cycle Assessment Approach to Facilitate Design Decisions on Sustainable Building Projects in Canada

Abstract

In the context of the digital and sustainable transformation of building projects, the integrated approach of Building Information Modeling (BIM) and life-cycle assessment (LCA) has been widely studied. Recent advancements in such integrated modeling processes and techniques have not yet provided reliable and robust decision-making capabilities for designers to intuitively choose between material alternatives. This study develops a new design framework that integrates BIM, LCA, and multi-criteria decision-making (MCDM) algorithms to facilitate sustainable design processes in building projects. A case study using a single-family housing project in the British Columbia province of Canada was implemented to test the designs to demonstrate the effectiveness of the proposed integrated framework, including a three-way comparison of design scenarios—conventional hot-roll steel, recycled steel, and timber. The results indicate a significant performance improvement with the adoption of recycled structural steel materials, surpassing conventional steel designs and demonstrating a similar performance to that of timber designs. The study underscores the importance of informed decision-making in material selection, driven by the quantitative analysis of digital designs and multi-criteria evaluation (e.g., social carbon cost). This integrated framework offers a valuable tool for designers, engineers, and builders to achieve sustainability when designing building projects through the systematic and rapid comparison of environmental performance.

1. Introduction

The construction sector has a substantial impact on global carbon emissions and plays a vital role in promoting sustainability. Recent research indicates that buildings and construction account for about 34% of global energy consumption and 37% of energy-related CO₂ emissions [1]. This significant environmental footprint is largely due to the use of high-carbon materials, such as concrete, and practices misaligned with emergent sustainability concepts such as the circular economy (CE). In the context of the built environment, the CE is defined as the strategic design of buildings to allow the easy modification of their configurations for increased longevity, thus supporting the continuous cycle of reduction, reuse, and recycling to enhance resource efficiency [2]. For example, CE methods such as the strategic use of by-products and waste materials in building material production and design for deconstruction or disassembly are perceived as effective in reducing both embodied and total carbon emissions [3]. However, the successful implementation of CE principles in the built environment demands meticulous design and planning to ensure buildings are sustainable, adaptable, and durable.

Building Information Modeling (BIM) is a model-based management process and a parametric design method that aids designers and engineers in efficiently planning, designing, constructing, and managing construction projects. It promotes stakeholder collaboration by lowering project costs, reducing material requirements, minimizing waste, and decreasing carbon emissions through improved site and logistics management [4]. Utilizing BIM also facilitates the evaluation of environmental impacts and the selection of sustainable alternatives [5]. Recent studies in sustainable construction emphasize the integration of BIM, life-cycle assessment (LCA), and CE principles to enhance environmental performance throughout all stages of a building’s life cycle [6,7]. This combination facilitates thorough environmental assessments, optimizes designs to address environmental issues early on, and manages complex data efficiently, thereby saving time and costs. Furthermore, the integration of circular economy principles with BIM and LCA not only mitigates the direct environmental impacts of construction processes but also promotes material efficiency and resource conservation throughout the building’s life cycle, leading to notable reductions in resource use and waste. This integrated way of designing and managing building projects streamlines the assessment process and improves its accuracy and relevance in sustainable building practices. For example, in [8], early design processes benefit from the successful integration of BIM and LCA to ensure design productivity. This synergy enhances project execution by enabling more informed decision-making, optimizing material selection, and minimizing waste. The recent developments in integrated BIM and LCA emphasize the significant potential for enhancing sustainability design solutions in construction through these collaborative methodologies.

Current practices also show that BIM has frequently been employed in various types of projects to assist the design phase and LCA has been utilized to evaluate the environmental impacts of construction materials. However, the decisions of engineers and designers often require deeper insight into the importance of design criteria and material choices. Multi-criteria decision-making (MCDM) is a possible method to fill this gap, e.g., assessing structural materials against multiple sustainability criteria supported in a BIM-LCA integrated assessment environment [9]. Therefore, the existing integrated BIM-LCA method can be further augmented by MCDM methods to add insights to the comparison of multiple design criteria and solutions. This integrated approach can be crucial for quantifying and prioritizing environmental impacts, thus improving the practical effectiveness of sustainability assessments [10]. Several MCDM methods have been discussed in the literature, including the analytic hierarchy process (AHP) [11], the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) [12], Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE) [13], the Decision-Making Trial and Evaluation Laboratory (DEMATEL) [14], and the fuzzy AHP [15].

The AHP, as an MCDM method, stands out by providing a mathematical methodology that integrates the preferences of decision-makers and stakeholders with technical data to optimally select solutions or categorize alternatives for specific challenges. Methods like the AHP are particularly valuable in environmental decision-making, where it is essential to balance conflicting socio-economic and environmental criteria [16,17]. By integrating BIM, LCA, and AHP, engineers and decision-makers are empowered to systematically assess and compare the long-term environmental, economic, and social impacts of their decisions, thereby enhancing the sustainability of construction projects [9]. In the study [15], researchers utilized a similar approach to propose a decision-making framework for construction professionals and researchers to select suitable materials for buildings.

Despite the growing importance of sustainable material selection in the construction industry, existing frameworks lack an integrated approach that combines digital tools and multi-criteria decision-making to address region-specific sustainability challenges. This study fills the gap by developing a comprehensive framework incorporating BIM, multi-criteria decision-making, and OneClick LCA to streamline material selection and facilitate stakeholder collaboration. This approach enables more accurate decisions within a reasonable timeframe by quickly analyzing various scenarios and comparing the impacts of different materials and designs to optimize project sustainability. In our study, we employed an approach by developing an integrated framework that combines the capabilities of digital tools and multi-criteria decision-making to facilitate material selection and support stakeholders in making sustainable choices in building projects. The proposed integrated approach of BIM-based LCA and AHP using the OneClick LCA software (version 0.27.3; database version 7.6) to select materials aimed to determine sustainable options for building projects. We compared existing designs with new proposals using OneClick LCA and its embedded material environmental product declaration data. The life-cycle performance analysis was based on 3D building models created in Revit, enabling us to track environmental impact across various phases, including construction, transportation, maintenance, and decommissioning.

So, our research specifically addresses the need for comprehensive decision-making for the specific climate conditions of Canada, social factors in LCA, the integration of digital tools, and a streamlined material selection process. Therefore, the key contributions of our study are summarized as follows:

• Aligning decision-making criteria with Canada’s diverse climate zones to ensure material selection and design choices meet regional challenges as well as acknowledging the role of local factors, such as typical materials used in designs, in the circular economy and sustainable choices;
• Considering social implications during the life cycle beyond environmental factors by using the social cost of carbon for different material choices;
• Enhancing material selection comparison and optimization through the integration of BIM and OneClick LCA;
• Enabling stakeholders to quickly analyze different scenarios, compare sustainability impacts, and collaborate using digital tools;
• Involving the circularity concept in the LCA of material choices along with sustainability criteria.

To test the usefulness of our BIM-LCA framework, we conducted a case study using a single-family housing model from a building company in British Columbia, Canada. Starting with a baseline assessment using conventional materials, we iteratively refined the design by integrating alternative materials. The final design outputs and comparisons can help stakeholders make rapid, environmentally responsible material decisions.

The remainder of this study is structured as follows: Section 2 provides a detailed literature review of sustainable design practices using BIM and LCA. Section 3 describes the proposed BIM-LCA design framework including the multi-criteria decision algorithms, elaborating the unique contribution to existing BIM-LCA design processes. Section 4 presents a case study of a residential housing project in BC Canada to demonstrate the usability of the proposed framework. Section 5 discusses the potential and areas of improvement of the proposed design framework, which is followed by conclusions and future work in Section 6.

2. Literature Review

2.1. Circular Economy Principles to Enhance Building Sustainability

Construction practitioners found that applying the CE guidelines might help the development sectors deliberately achieve the Net Zero emissions objective by 2050 [2]. The recommendation from the study [18] states that CE ought to center on lessening the negative impacts of natural items, expanding item life expectancy, and utilizing maintainable assets, which are basic to natural assurance. Circular development models can maximize the financial and natural benefits inserted in items and materials, such as by utilizing auxiliary materials to supplant the essential materials [19]. To handle the asset exhaustion challenges in present-day society, there has been a huge move towards a CE within the built environment to reduce the weight of non-renewable assets [20].

In the circular economy, the focus is on maintaining building components and functions at their best for as long as possible, promoting a continuous cycle of use, reuse, repair, and recycling to reduce waste and greenhouse emissions.

Some studies have already proved the benefits of the adaptive reuse of construction materials and using the existing built environment as a source of reusable components [21,22]. The components from old buildings can be reused and circulated through methods, such as improving or extending existing components on-site, moving the existing components to new locations, or reusing the demolished components from the old building [23]. In addition, the study [18] proposed the prefabrication and modularization of components, which facilitates the design of reused building products. Furthermore, disassembly and 3D printing technologies have become important in closing resource loops and optimizing material usage in construction in the short-term period in the Ellen MacArthur Foundation, and they encourage the broader acceptance of access-based business models in the long term. Simultaneously, the United Kingdom Green Building Council (UKGBC) has published an outline of CE strategies for construction sectors. It highlights the partnership between construction companies and manufacturing companies, stating that constructors should return disassembled construction materials to manufacturing factories and manufacturers should design structures and facades with reversible mechanical fixings. Sustainable construction guidelines with CE concepts were released by the Association of Cities and Regions (ACR) Sustainable Resource Management from an urban planning perspective. They emphasize social, landscape, and cultural aspects in constructing new constructions, including modularity, adaptability, and the use of recycled and reclaimed materials [24]. An international collaboration between the United Nations Economic Commission for Europe (UNECE), UN-Habitat, and the International Telecommunication Union (ITU) on circular and sustainable smart cities with an emphasis on enhancing Industrial Symbiosis with the use of information communication technology has been published. By working together, this collaborative effort aims to increase the flow of raw materials in the construction industry by connecting waste produced by one department with the raw material requirements of another.

While strategies for recycling construction and demolition waste are prevalent, efforts focusing on reuse are less common. Construction practitioners face challenges in understanding which building materials can be reused and to what extent carbon emissions can be mitigated through design and construction approaches such as designing for future reuse or incorporating recycled materials. This highlights the need for further research and guidance in promoting reuse within the construction industry.

Nowadays, in the construction field, green building standards increasingly incorporate aspects of the circular economy into their frameworks, recognizing the importance of sustainability and resource efficiency. While there is not yet a universally adopted circular economy standard specifically tailored for the construction industry, several existing green building standards address various aspects of the circular economy in their criteria and evaluations.

LEED (Leadership in Energy and Environmental Design) [25], for example, encourages strategies such as material reuse, recycling, and life-cycle assessment to minimize waste and promote resource efficiency. LEED also awards points for using materials with recycled content and for incorporating salvaged or repurposed materials into building projects. Similarly, the BREEAM (Building Research Establishment Environmental Assessment Method) [25] certification includes criteria related to material sourcing, life-cycle impacts, and waste reduction. BREEAM assesses the environmental performance of buildings across various categories, including materials, energy, water, and waste.

The LBC (Living Building Challenge) [25] takes a holistic approach to sustainability, emphasizing regenerative design principles and requiring projects to meet rigorous performance standards, including net-zero energy and water, as well as limitations on embodied carbon and toxic materials. The challenge also encourages projects to incorporate principles of the circular economy, such as designing for disassembly and promoting material reuse and recycling.

2.2. Integrated BIM and LCA Methods to Deliver Sustainable Designs

To evaluate and analyze the environmental sustainability of buildings and structures, various LCA systems and tools have been developed and tested. It is possible to categorize these tools into qualitative and quantitative categories. The qualitative method is more suitable for individuals who are not familiar with sustainable construction. Prominent examples in the qualitative realm include the Leadership in Energy and Environmental Design (LEED) and the Building Research Establishment Environmental Assessment Method (BREEAM), with both methods undergoing regular updates to meet the current construction market demands and requirements [26]. Furthermore, there are numerous LCA-based pieces of software and tools that are popularly used around the world, such as Athena, the Building Environment Assessment Tool (BEAT), EcoEffect Envest 2, the Environmental Load Profile (ELP), Eco-Quantum, and Sustainable Building. For quantitative methods, there is still a lot of well-developed software, including SimaPro, GaBi, and Umberto, which facilitate the calculation of environmental impacts across the life cycle of processes [27]. Nevertheless, it is essential to acknowledge three significant limitations: the necessity of expensive licenses for accessing certain tools, the requirement of specialized expertise to conduct comprehensive LCA analyses, and a substantial amount of data, which can be time-consuming and costly to gather.

Building Information Modeling (BIM) has become one of the most useful tools in modern construction sectors. It improves the coordination between design and construction departments. With a sustainability goal, BIM-based design integrates LCA considerations into material information and parametric building design data from BIM-based software. The BIM-based LCA analysis tools have established themselves as a valuable technique for sustainability assessments in the construction field and hold the potential for extension into circular economy (CE) research [2]. The studies presented in [28] and [29] developed BIM-based LCA software (Autodesk Revit, version 2023.1.3) to contribute to real-world building design processes, which help the designers make decisions within the evolving BIM model. The limitations include the need for further research to define information requirements for energy simulation and material impact assessments in BIM-integrated LCA, the necessity for comprehensive building element databases to optimize LCA applicability, and the requirement for expanded LCA databases to encompass new technologies and alternative construction materials for comprehensive assessment and visualization. Overall, existing research studies in this area do not completely provide a suitable solution to address the circular concepts in building design stages.

An approach to foster the CE involves utilizing material circularity assessments through BIM-based LCA, seamlessly integrating sustainable building regulations and environmental product declarations (EPDs) directly within BIM authoring software. Regrettably, relevant research on the CE within the built environment remains scarce in the current literature. Several scholars have highlighted the benefits of the circular rconomy (CE), especially Joensuu et al. [30]. Therefore, utilizing BIM and LCA tools to guide innovative design is crucial.

2.3. MCDM in Building Design Applications

Multi-criteria decision analysis is crucial in construction for considering the perspectives of stakeholders and making decisions related to various aspects of a project, such as quality, security, ethics, finance, and human resources. Many decisions made during the design stage involve multiple criteria that need to be analyzed to ensure optimal decision-making. Several methods in the scientific literature support strategic decision-making, including mathematical optimization and the analytic hierarchy process (AHP). Implementing MCDA methods is encouraged to generate effective and sustainable solutions in construction, but it requires the development of systematic tools and methods.

The analytic hierarchy process (AHP) is a widely used and preferred method for multi-criteria decision-making (MCDM) to address problems involving criteria prioritization [31,32]. This ranking technique is a straightforward method of minimizing opinion inconsistencies and generating judgments based on several criteria, which has drawn the attention of numerous academics across multiple domains [33].

In order to choose the most environmentally friendly façade solution among five options to replace the deteriorating façade of a real building, considering environmental, social, and economic criteria in the analysis, the study [12] used the Delphi and AHP methodologies. Using fuzzy AHP, the study [34] developed a model for choosing environmentally friendly building materials for single-family homes in the UK. The FAHP approach improves its precedent, the analytic hierarchy process (AHP), by including fuzzy logic theory [35]. AHP is founded on Newtonian and Cartesian thinking, which entails breaking down a problem into smaller sections as many times as needed until a precise and scalable level is achieved. Making paired comparisons using a basic scale ratio inside a hierarchy is the main objective of the AHP approach [36].

To better discover this area, a few similar studies were reviewed. A study by Yubing Zhang et al. [37] provided comparative analysis results of carbon emissions for different building design stages and weather, highlighting the effectiveness of integrating BIM with LCA for sustainability assessment. Additionally, it discusses the implications of carbon emissions on public health, emphasizing the importance of considering broader environmental and social impacts in construction projects with a case study in China.

Furthermore, another study from Mohammad Najjar et al. [38] demonstrates the effectiveness of the BIM-integrated approach in facilitating sustainable building design and evaluation through a real-world case from Brazil. By considering public health alongside environmental factors, such as acidification potential, eutrophication potential, global warming potential, ozone depletion potential, smog formation potential, primary energy demand, non-renewable energy, and renewable energy, the approach enables stakeholders to make more informed decisions that address broader sustainability objectives.

Karoline Figueiredo et al. [14] identify new strategies and best practices for integrating BIM and LCA in the early design stages of construction projects, which combine the integrating Life-Cycle Sustainability Assessment (LCSA), Multi-Criteria Decision Analysis (MCDA), and Building Information Modeling (BIM) together to find the most sustainable choice of construction materials. This LCSA-BIM-MCDA framework emphasizes the importance of considering social economic factors alongside environmental concerns to achieve holistic sustainability goals.

Abdelaal and his team [9] demonstrate the effectiveness of the BIM–LCA–AHP approach in concrete structure design and sustainable building evaluation. By considering the CO₂ emissions of different types of concrete, the energy consumption, and construction cost, the approach helps stakeholders make better selections of the construction material to reach sustainability goals.

Ming Hu [39] introduces a new LCA–MCDA method, which includes the analysis of the impacts of the environment, water, and human health by using the data from the Living Building Challenge (LBC). It aims to evaluate the impacts of different main categories of the different materials, which is an auxiliary method to help the stakeholders to achieve comprehensive sustainability goals.

Based on the literature, it can be noted that there is a need to develop an integrated framework that incorporates the capabilities of digital tools and multi-criteria decision-making to facilitate material selection and assist stakeholders in identifying sustainable choices. This approach enables more accurate decisions within a reasonable timeframe. It can quickly analyze various scenarios, comparing the impacts of different materials and designs to optimize the sustainability of the project.

To address this gap, this study integrates the existing BIM-LCA approach with decision-making capabilities and delves into a case study involving three types of material (conventional steel design, alternative steel design, and timber design) leveraging the OneClick LCA software (version 0.27.3; database version 7.6) to evaluate material circularity. Comparative results will provide stakeholders, particularly considering the environmental situation in Canada, with insights into optimal material choices. Based on the findings of this study, an LCA process based on BIM is proposed to compare the carbon impact of two design model alternatives using different material choices, including virgin materials, recycled materials, and reused materials.

3. Materials and Methods

Based on the literature review and identified gaps, this study highlights the need for the development of a method capable of assessing various material choices throughout the building life cycle based on environmental and social criteria. Moreover, this method requires considering the importance of each of these criteria in the assessment process. Therefore, in this research, an attempt was made to address these objectives by selecting suitable tools using an integrated method. In this regard, BIM was employed as a powerful tool for designing buildings using available material choices. This tool can provide a precise estimation of the properties and quantity of the materials used in a digital environment with a high accuracy and in minimal time [9,10]. Subsequently, for conducting a life-cycle assessment, the outputs of the models generated by the BIM tool were utilized again, and with the assistance of LCA plugins, such as One Click, a detailed assessment of the defined criteria can be presented. Alongside these tools, there was a need to determine the relative importance of the identified criteria. In this regard, expert opinions were taken into account using the analytic hierarchy process (AHP) to make this method more practical and aligned with the challenges [11]. Accordingly, the proposed framework is an integrated decision support tool that combines LCA with the AHP method to rank a list of material choices. From this ranking, the most suitable materials and design can be selected for the building project, taking into account social and environmental criteria. This framework encompasses various phases, which are described in the following (see Figure 1). The developed framework in this research consists of 6 main steps. Initially, based on the available information, BIM models were developed and designed (Step 1), and with the help of these models, further details regarding the properties and quantity of materials used in the design were provided (Step 2). Subsequently, with the assistance of the results obtained from the previous step and using the BIM model, LCA for the selected material was conducted (Step 3). In the next step, with the help of the multi-criteria decision-making method (MCDM), the weights of each criterion for evaluating different material choices were determined (Step 4), and based on the results of this stage and Stage 3, ranking of various options (Step 5) was carried out for selection among them considering the environmental and social criteria defined (Step 6).

Step 1: Parametric building designs: In the initial phase, selections of both old materials and potential alternatives are input into BIM models. These models then guide the creation of building designs, consolidating various aspects of architectural, structural, and MEP (Mechanical, Electrical, and Plumbing) components. The developed 3D models determine the general specifications of the project, offering a detailed and tangible representation for examination and visualization. A particularly significant feature of these models is their ability to generate accurate estimates of the required material specifications and quantities, which is crucial for conducting life-cycle assessments. Moreover, using BIM enables us to have a cost estimation of the required materials and brings about valuable insight regarding economic comparisons between different material choices.

Step 2: Material Properties and Quantity: Subsequently, in this phase, determinations are made regarding the necessary properties and quantities of materials, based on the BIM models. This step involves a careful assessment of established material choices—typically those that have been conventionally used—and innovative alternative materials that may offer improved sustainability or distinct benefits compared to the old selections.

Step 3: BIM-based LCA: LCA is used for assessing some of the environmental and social aspects and potential impacts associated with various BIM models. In this regard, the OneClick LCA extension is used to measure the environmental and social impacts of materials based on predefined criteria and BIM models.

Step 4: Multi-Criteria Decision-Making Method: At this stage, we apply a multi-criteria decision-making method to assess the various criteria used in the previous step. For this study, we utilize the AHP approach. The objective at this point is to establish priorities and determine the weights of the used criteria in Step 3.

Step 5: Ranking of Material Choices: In the ranking of material choices step, values are assigned to related criteria based on their assessments. These values are then weighted to reflect the relative importance of each criterion. The resulting weighted values are used to develop a ranking for the material choices.

Step 6: Choice of Material and Design: Finally, the decision support tool provides a ranked list of material choices. This ranked list aids decision-makers in determining which materials are the most sustainable and appropriate for the project within the available options.

3.1. BIM-Based LCA Processes

This study employs a BIM-based LCA process specifically tailored to calculate carbon emissions in buildings, considering a range of design options and material selections. The software is equipped with algorithms for assessing building circularity, with detailed explanations of these calculations are available through the One-Click LCA online help center. One-Click LCA streamlines the quantification of environmental impacts, significantly reducing the need for manual data entry. Additionally, One-Click LCA’s extensive EPD (environmental product declaration) database allows users to customize their LCA studies with specific geographical conditions and preferences.

Our BIM-based LCA anchors on a series of environmental and social indices defined in OneClick LCA, derived from authoritative studies, and recognized as global standards in environmental project assessment, as encapsulated within the LEED building rating framework [40,41]. These indices encompass a range of environmental and social concerns as indicated in

Table 1. LCA environmental and social factors.

LCA Factor	Unit	Category	References
Global Warming	kg CO2e	Environmental	[40,41]
Ozone Depletion	kg CFC11e	Environmental	[40,41,42]
Acidification	kg SO2e	Environmental	[40,41,43]
Eutrophication	kg Ne	Environmental	[40,41,43]
Formation of Tropospheric Ozone	kg O3e	Environmental	[40,43]
Depletion of Non-Renewable Energy	kWh	Environmental	[40,41,44]
Social Cost of Carbon	USD/kg CO2	Social	[40,41,45,46]

.

Incorporating established criteria, the OneClick LCA tool enables the rigorous evaluation and determination of the performance of each alternative building project across various criteria. Additionally, we incorporate an evaluation of the building’s circularity, assessing its potential for reducing waste through reuse and recycling. This feature of the software not only enhances the LCA but also provides actionable insights for optimizing the circularity of the project.

3.2. Integrating MCDM with Existing BIM-LCA Processes

The integration of AHP with LCA includes constructing a pairwise comparison matrix, which represents the relative importance and uncertainty of various criteria, such as carbon emissions, energy usage, and material toxicity. Initially, a survey among experts in the field qualitatively assesses the importance of each criterion. This process advances by synthesizing these expert judgments to derive priority weights that incorporate both the quantitative data from LCA and the qualitative assessments typical of AHP [31]. In the questionnaire, participants rate the relative importance of criteria on a numerical scale from 1, indicating neutral importance, to 9, indicating significantly greater importance. The gathered responses are transformed into deterministic numbers. The final weights of the criteria are calculated by aggregating the values across each matrix row to produce a single number per criterion, which is then normalized to a total one, reflecting the relative importance of each criterion in the decision-making process [15,47].

3.3. Determining the Design Criteria Weights from the MCDM

To obtain the design criteria weights, this study collected expert opinions on sustainable building design through a survey regarding the extent of environmental and social factors affecting the choice of material. An example survey question in Excel format that requests expert opinions on the pairwise comparison of design criteria is shown in Figure 2. The survey questions were distributed to 13 civil engineering professionals, with 9 respondents providing their preferences among criteria related to material sustainability. All participants possessed practical experience in the construction industry and a minimum of two years of expertise in LCA approaches. Among them, five were Project Managers, and three specialized in sustainability-focused projects. The questionnaire tasked engineers with conducting pairwise comparisons among the material sustainability criteria outlined in the study (Figure 2).

Subsequently, the arithmetic mean of responses from the seven participating professionals was calculated for each pairwise comparison. These averaged responses served as the foundation for further analysis, as outlined in the subsequent stage of the proposed framework (see

Table 2. Results of the pairwise comparison questionnaire based on AHP.

Factors	Global Warming (C1)	Ozone Depletion (C2)	Acidification (C3)	Eutrophication (C4)	Tropospheric Ozone (C5)	Non-Renewable Energy (C6)	Social Cost of Carbon (C7)
Global Warming (C1)	1	7	7	7	7	7	7
Ozone Depletion (C2)	0.14	1	7	7	7	0.11	0.14
Acidification (C3)	0.14	0.14	1	7	7	7	7
Eutrophication (C4)	0.14	0.14	0.14	1	7	7	7
Tropospheric Ozone (C5)	0.14	0.14	0.14	0.14	1	5	5
Non-Renewable Energy (C6)	0.14	9	0.14	0.14	0.20	1	7
Social Cost of Carbon (C7)	0.14	7	0.14	0.14	0.20	0.14	1
TOTAL	1.86	24.43	15.57	22.43	29.40	27.25	34.14

).

Following the calculation of the criteria weights, the evaluation process for the alternatives was initiated. The environmental and social Life-Cycle Impact Assessment (LCIA) results for the two different material alternatives for the building were normalized. These normalized values served as the weights.

The normalization of the resultant pairwise matrix (

Table 3. The normalization of the resultant pairwise matrix.

Factors	(C1)	(C2)	(C3)	(C4)	(C5)	(C6)	(C7)	Weights	In Percentage
(C1)	0.5385	0.2865	0.4495	0.3121	0.2381	0.2568	0.2050	0.3267	32.6659
(C2)	0.0769	0.0409	0.4495	0.3121	0.2381	0.0041	0.0042	0.1608	16.0837
(C3)	0.0769	0.0058	0.0642	0.3121	0.2381	0.2568	0.2050	0.1656	16.5579
(C4)	0.0769	0.0058	0.0092	0.0446	0.2381	0.2568	0.2050	0.1195	11.9499
(C5)	0.0769	0.0058	0.0092	0.0064	0.0340	0.1835	0.1464	0.0660	6.6033
(C6)	0.0769	0.3684	0.0092	0.0064	0.0068	0.0367	0.2050	0.1013	10.1343
(C7)	0.0769	0.2865	0.0092	0.0064	0.0068	0.0052	0.0293	0.0600	6.0050
Total	1	1	1	1	1	1	1		100

) involved dividing each element of the matrix by the sum of its respective columns, resulting in the generation of a normalized matrix. Subsequently, the weights assigned to each criterion were computed by aggregating the normalized values across each row. This procedure yielded the percentage representation of the factors influencing the selection of sustainable materials among the evaluated alternatives in this study [14].

The analysis of the resultant values revealed the hierarchy of criteria significantly impacting sustainable material selection. Global warming emerged as the foremost influential factor, succeeded by ozone depletion, acidification, and eutrophication. Conversely, criteria such as the social cost of carbon and non-renewable energy exhibited comparatively lesser influence, followed by tropospheric ozone. The calculated consistency index (CI) of the pairwise matrix using the Principal EigenValue was 0.0159. Furthermore, the Random Index (RI) for 7 factors was 1.32. Accordingly, the consistency ratio (CR) of the criteria pairwise comparison matrix was calculated to be 0.012, which falls below the threshold of 0.1 [14], indicating a consistent and acceptable result. This validation ensures the reliability of the pairwise comparisons made in the study.

4. Case Study: Single-Family Housing Project Design in BC, Canada

4.1. Project Description and Software Setup

The single-family housing project was located in Nanaimo, the British Columbia province of Canada. The initial 3D design model details were provided by a prefabricated home company in Canada. As a baseline, an LCA was performed for a default design using common materials. In the subsequent step, by utilizing the obtained results and replacing materials with more circular and sustainable choices, the initial design was then enhanced and the proposed method was subsequently applied to the alternative choices.

As mentioned previously, initially, utilizing the 3D model developed in the Revit software (version 2023.1.3) (Figure 3), the general specifications of the project were determined, providing a detailed and tangible representation for examination and visualization. Another significant aspect of this model is its capability to generate an accurate estimate of the specifications and quantities of materials required. This feature plays an important role in conducting a life-cycle assessment. Following this, the model was initially designed based on common materials, and the results of the life-cycle assessment were presented using the OneClick LCA plugin.

Before delving into the detailed results of each scenario, considerations related to the setup and customization of using this plugin in 3D Revit models are presented. This plugin is easily added and installed in the Revit software environment, with user-friendly capabilities for utilization. After installing and launching the plugin, initial settings are configured based on the assumptions in the case study. These assumptions may include factors, such as the type of the building under investigation, the building’s gross area, the project location, the preferred system for conducting the LCA, and so forth.

Another important aspect at the beginning of using this assessment is mapping the materials used with predefined databases to identify the EPD (environmental product declaration) of the materials and perform assessments based on the specified characteristics of each material. In this section, the One Click LCA database is utilized for defining the materials (Figure 4). In the next step, by replacing the previous materials used in the conventional steel design with more sustainable and circular ones, the design is enhanced, and the results of the life-cycle assessment for the new steel design are presented. Subsequently, a timber house is analyzed to provide more practical results.

4.2. Conventional Design Using Hot-Rolled Steel (Steel 1 Design Scenario)

As mentioned, in the initial design, the materials predominantly consisted of conventional materials commonly used in older designs. For example, fabricated hot-rolled structural steel sections were used for frames and structural elements in the building design. Additionally, typical XPS insulation and conventional aluminum windows were used. Moreover, it should be noted that the LCA for LEED, Canada (TRACI), was conducted in this case study. First, the results of the life-cycle overview of global warming for this design are discussed. As depicted in Figure 5, materials constitute the majority, with an approximate 90% global warming potential in this design. Following that, waste processing accounted for 6.5%. Upon examining the primary resources contributing to the global warming potential of this building, it was evident that the steel profiles and structural elements used played a significant role. Following them, components related to XPS insulation and plastic products were included (Figure 6).

In addition, the results related to other environmental indicators, categorized by the life-cycle stages of the building, are summarized in Figure 7.

Another important result obtained by conducting the LCA on the 3D model was carbon heroes benchmarking. This result was determined based on the standards of various countries, and in this research, the model defined for Canada was used as the reference pattern. Embodied carbon benchmarks were calculated for a fixed 60-year assessment period for all building materials, materials transport, and material replacements required during the building assessment period as well as the end-of-life processing. The impacts were calculated on a per Gross Internal Floor Area (m²) basis. The benchmark for this design is provided in Figure 8.

Additionally, the social cost of carbon was another output of this analysis. This indicator was estimated to be EUR 7459 based on the LCA conducted for this design.

Another valuable result provided by this tool is evaluating the circularity of the design. In this regard, this plugin provides a circularity index in order to assess different aspects of this concept based on the design developed in 3D models. According to the definition provided by OneClick LCA, “the building circularity score represents the total materials circularity both in use of materials for the project as well as the end-of-life handling”. It is calculated as the average of Materials Recovered (representing the use of circular materials in the project) and Materials Returned (representing how effectively materials are returned, instead of disposed of or downgraded in value). The results of this analysis for this design are depicted in Figure 9.

4.3. Alternative Design Using Recycled Steel (Steel 2 Design Scenario)

In the second design, efforts were made to use materials with fewer adverse environmental effects and greater compliance with sustainability principles. For this reason, some of the previous materials that had a significant role in negative environmental impacts were replaced with new materials. Moreover, in this design, the chosen materials were more aligned with circularity concepts. This replacement was carried out after evaluating the EPDs of various materials and using the 3D model and LCA plugin. One of the main materials that contributed to the improvement of the environmental performance of this design was recycled cold-rolled steel, which also has significant reuse end-of-life capacities.

Similar to the previous design, LCA results were provided via the following steps. First, the global warming impact of this design was assessed based on life-cycle stages. The results illustrated the materials, waste processing, and replacements that contributed the most to global warming (Figure 10). Moreover, it could be observed that, in this design, due to the use of recycled cold-rolled steel profiles, their role in global warming impacts significantly decreased compared to the previous design. It was noted that elements related to insulation contributed the most to this indicator (Figure 11). Moreover, the conventional aluminum window frames were replaced by more sustainable products.

Furthermore, the results related to other environmental indicators, categorized by the life-cycle stages of the building for the alternative design, are summarized in Figure 12.

Additionally, the carbon heroes benchmark for this design was estimated as provided in Figure 13. It can be concluded from this result that replacing previous materials with more sustainable choices can play a significant role in alleviating the adverse environmental impacts of buildings since this indicator was reduced by 59.87%.

Finally, it should be mentioned that the estimated social cost of carbon for this design was EUR 2370, which experienced a significant reduction compared to the previous design. This indicator experienced a 68.22% reduction, providing further evidence of the improvements in the design of the building during its life cycle.

With the replacement of the previous materials with newer ones that adhere more to circularity principles, we can observe a significant improvement in the building circularity score in this design. As shown, both recycling and recovering the materials used increased, leading to an enhancement in the environmental performance and circularity of the building (Figure 14).

4.4. Timber Design (Timber Design Scenario)

In this scenario, plain wood/timber was used instead of steel elements, and other details of the design were addressed regarding this change. In the following sections, the results of this design are provided.

The LCA results indicate that using timber in the structure of this design can provide an environmentally acceptable performance throughout its life cycle. As illustrated in the figure below, materials contributed the most significant share in global warming (Figure 15). Following that, waste processing made a considerable contribution. Among the materials used, the materials employed in insulation, plastic products, and then wood were effective in the global warming index (Figure 16).

Furthermore, the results related to other environmental indicators, categorized by the life-cycle stages of the building for the timber design, are summarized in Figure 17.

Furthermore, the carbon heroes benchmark for the timber design is depicted in Figure 18. As is shown, this design provided a more sustainable output than the first scenario. However, the performance of this scenario and the second one, in which more sustainable materials, such as recycled cold-rolled steel, were used, provided very similar results. The design using timber only slightly improved in terms of this indicator.

The estimated social cost of this scenario was estimated to be EUR 1930, which shows a notable improvement in comparison with previous scenarios, especially the conventional design.

In this scenario, circularity was also evaluated using the tool developed in the plugin. Considering the relatively good recycling and recovering capacity of wooden components in the building, the circularity score was better compared to scenario one. However, due to the improvement in the selected materials in scenario two (using cold-rolled recycled steel), this design demonstrated relatively less circularity capability.

4.5. Ranking Design Scenarios and Material Choices

In the final step, by synthesizing the results obtained from the LCA and AHP method, it was possible to proceed to summarize and make the final comparison of the choices of materials. In this step, as shown in the table below, the weights obtained from AHP and the results from the LCA, normalized by dividing over the lowest figure and making it 1, were utilized to determine the final score for each scenario. It is worth mentioning that, since the defined indicators relate to the adverse environmental and social impacts, such as emissions, costs, and depletion, the higher the calculated figure, the poorer the performance of the selected materials. In this case study, as observed, the performance associated with the conventional steel design was the weakest. However, by employing more sustainable and circular materials, a significant improvement in the performance was evident. Regarding the timber option, although it was considerably better than the conventional steel design, there was not much difference compared to the improved steel design. The results are provided in

Table 4. Results for ranking the three design scenarios and material choices.

			Not Normalized			Normalized
Indices	Weights	In Practice	Steel 1	Steel 2	Timber	Steel 1	Steel 2	Timber
Global Warming (kg CO2e)	0.326	32.665	149,190	47,399	38,596.300	3.865	1.228	1.000
Ozone Depletion (kg CFC11 e)	0.160	16.083	0.005	0.004	0.003	1.655	1.241	1.000
Acidification (Kg SO2e)	0.165	16.557	496.150	217.350	172.140	2.882	1.263	1.000
Eutrophication (Kg Ne)	0.119	11.949	52.720	91.840	43.870	1.202	2.093	1.000
Tropospheric Ozone (Kg O3e)	0.066	6.603	4620	2264	2032	2.274	1.114	1.000
Depletion of Non-Renewable Energy (MJ)	0.101	10.134	1,090,847	196,788	207,170	5.543	1.000	1.053
Social Cost of Carbon (EUR)	0.060	6.004	7459	2370	1930	3.865	1.228	1.000
TOTAL		100				3.093	1.308	1.005

.

5. Discussion

This research presents an integrated methodology composed of BIM, LCA, and AHP to evaluate the environmental and social criteria of different material choices. This methodology was applied to a building case study in British Columbia, Canada. Similar studies emphasize the capabilities of integrated methods in selecting between various material choices. For instance, the use of BIM and LCA integration in early design stages to improve a building’s environmental performance has been studied [38]. However, our study also highlights the use of expert opinions to determine the relative importance of selected criteria through the AHP method, in order to provide more practical results. Furthermore, in another similar study presenting an integrated BIM and interview-based method, the possibility of a more sustainable design based on defined criteria evaluated by MCDM was demonstrated [48]. However, the use of life-cycle assessment allows for a more dynamic evaluation and takes advantage of BIM’s extensive capabilities. Lastly, another comparable study based on an integrated method combining BIM, LCA, and fuzzy AHP also confirmed the capabilities of this methodology [14]. Nonetheless, we aimed to provide a broader range of environmental and social criteria in this study as well as incorporating the circularity concepts of material choices in order to address a more sustainable and circular design.

In this section, some of the limitations as well as the advantages of the proposed method are discussed. Firstly, one of the main limitations of the proposed method is its reliance on predefined databases such as EPD. This limitation arose when some of the material properties required for use in existing choices were not defined in the databases. In such cases, there was a need to manually define some of these properties or use properties of materials that are similar to the desired material. Another point that can be considered as a limitation of this methodology is the fact that the AHP method inherently relies on expert opinions, introducing a degree of subjectivity into the decision-making process. We acknowledge this potential bias and suggest implementing several measures to enhance the objectivity and reliability of our study. Comparing the AHP results with outcomes from an alternative multi-criteria decision-making method, such as TOPSIS, will demonstrate consistency between the methods. Also, the incorporation of more diverse expert opinions in the AHP method will provide a broader perspective and minimize individual biases. Including a wider range of individuals skilled in different fields not only enriches the analytical process but could also yield significant insights regarding the relative importance of environmental and social indicators. This diversity is crucial as it allows for a more comprehensive evaluation of the complex variables that these indicators represent. Therefore, it is imperative to address this limitation in future research by adding additional professionals and experts to fine-tune pairwise comparisons. Such an enhancement will undoubtedly improve the robustness and applicability of the findings, making them more representative of varied perspectives and expertise. Additionally, another limitation of this method is the definition of more social indicators. Given the importance of social performance in sustainability principles, this point can be further highlighted and addressed. Another limitation to consider is that this research focuses on the results of studying a specific type of building. One aspect that can be considered is the impact of different elements of buildings, such as design details, the number of floors, and so forth, on their environmental and social performance. It is worth noting that the results presented in this study were derived from the implementation of the developed method on a specific case study. It is expected that examining different cases situated in other locations, which also differ in terms of building characteristics and material choices, could lead to different results. Additionally, as mentioned, the expert opinions played a significant role in determining the priority of the criteria. Therefore, increasing the number and diversity of these opinions could also lead to different results.

On the other hand, among the advantages and capabilities of this approach, prioritizing expert opinions in determining the priority of indicators can be mentioned. This allows the results of the assessment to become more practical and gain more acceptance and attention in real-world cases. Moreover, referring to MCDM approaches and incorporating multi-criteria evaluation in this study demonstrates the theoretical importance of considering a broad range of social and environmental criteria beyond purely technical aspects in sustainability decision-making [49]. Furthermore, this method was able to provide comprehensive results for decision-making regarding material choices by employing the LCA method. In this regard, decision-makers will be able to access reliable results on the performance of different options throughout the building life cycle before entering the design and implementation phases, with minimal time and cost. In addition, the extensive capabilities added to this method through the use of BIM is another advantage. As mentioned, the use of BIM allows for the consideration of multiple and diverse designs for various cases with very high accuracy and speed, enabling the selection of the best available options. Among other capabilities, BIM enables the visualization of buildings, which will have a significant impact for various stakeholders. Additionally, BIM allows for the inclusion of economic indicators in the assessments. Hence, alongside environmental and social indicators, a thorough examination of the economic performance of the available choices can be provided. By using and integrating BIM, LCA, and MCDM, this study also contributes to theoretical insights for more comprehensive, systemic, and structured sustainable decision-making in building projects. Moreover, the analyzed case in this research demonstrates the framework’s adaptability, which could extend to various types of building projects beyond single-family housing. This scalability highlights the potential applicability of the framework to different regions and building standards, providing a basis for further theoretical exploration in diverse contexts. In addition, by including the concept of social carbon cost in the evaluation, the paper provides theoretical insights into the broader social impacts of building material selection. Finally, the research highlights the performance of regional material alternatives, such as recycled structural steel and timber. By comparing these to conventional hot-rolled steel, the paper supports efforts to use locally available and sustainable materials, which can help boost local economies and reduce the environmental impact associated with long-distance transport [50].

6. Conclusions

Despite recent progress in integrating BIM and LCA for sustainable design innovations, delivering reliable decisions on the design alternatives by properly weighing the multiple material choices and performance indicators remains a challenge in practice. This study addresses this by introducing a novel design framework that levels up the existing BIM-LCA approach by embedding the MCDM algorithms in the design evaluations, facilitating rapid and sustainable design processes in construction projects. Through a case study of the single-family housing project in the British Columbia province of Canada, the effectiveness of this integrated approach was demonstrated in the comparison of three design scenarios to evaluate their environmental performance—conventional hot-roll steel, recycled steel, and timber. The results show that adopting recycled structural steel materials leads to significant improvements in performance, outperforming conventional steel designs and aligning closely with timber alternatives. Emphasizing the importance of informed decision-making, the study highlights the role of quantitative analysis and multi-criteria evaluation, such as assessing social carbon costs.

Though the proposed design framework leverages the digital parametric design from BIM, the integration of the updated EPD material database and dynamic MCDM modeling techniques could substantially enhance the accuracy and responsiveness of this integrated framework, allowing for more adaptive and proactive decision-making during the early design phase. Expanding the scope of the study to include a broader range of building typologies and geographical locations would also provide a more comprehensive understanding of the proposed framework’s applicability and effectiveness across diverse contexts. Moreover, the refinement and optimization of the MCDM algorithms to better accommodate the complexities and uncertainties inherent in sustainability and circularity assessments represent a promising avenue for future CE research in the construction industry.