Monetizing Environmental Impacts into Environmental Costs During Prefabricated Building Construction: A 5D BIM-Enabled Analysis

Abstract

Although prefabricated buildings offer environmental advantages, their construction process inevitably generates environmental impacts. However, current research on prefabricated buildings focuses on the environmental impact level, and there is a lack of intelligent tools for analyzing their spatial and temporal dimensions. Therefore, this study develops a framework using 5D building information modeling (BIM) to monetize environmental impacts into environmental costs for prefabricated building construction. This framework includes defining boundaries and indicators, obtaining a resource inventory using the 5D BIM coding system, calculating environmental impact results, and converting environmental impacts into environmental costs. Taking a prefabricated substation as a case study, its environmental costs are 172.81 CNY/m², with these costs caused by climate change accounting for the largest proportion (91.2%). This study unifies different environmental impacts into a single monetary form, providing stakeholders with intuitive indicators. It also expands 5D BIM applications from conventional costs to environmental costs, which can display their spatiotemporal changes.

1. Introduction

The construction industry accounts for nearly 40% of global raw material consumption, 36% of energy consumption, 40% of solid waste generation, and 40% of greenhouse gas emissions [1]. To mitigate the environmental impacts of construction projects, prefabricated buildings, characterized by industrialized production methods [2,3], have emerged as a growing trend in the construction industry [4].

Nevertheless, the construction process of prefabricated buildings still inevitably exerts environmental impacts [5,6]. For example, the production, transportation, and assembly of prefabricated components consume energy and generate pollutant emissions, such as greenhouse gas emissions, ozone layer depletion, and particulate matter formation [7]. These environmental impacts not only cause damage to ecosystems but also pose potential threats to human health and socioeconomic development [8,9]. To evaluate these environmental impacts, some studies compared prefabricated buildings with conventional buildings [10,11,12,13] and also explored the impact of different assembly rates [14].

However, current research on prefabricated buildings is still confined to environmental impact assessment. The units of these environmental impacts vary; for example, greenhouse gas emissions are measured in kgCO₂ [12,15], energy use in MJ [16], and particulate matter formation in kgPM10 [13]. This unit disparity makes it difficult to standardize different environmental impacts to a common benchmark. More importantly, without monetizing these environmental impacts, stakeholders cannot intuitively understand their negative economic effects.

On the other hand, building information modeling (BIM) provides a more efficient and accurate tool for the environmental impact assessment of prefabricated buildings [7]. Additionally, 5D BIM technology has effectively facilitated quantity surveying and cost management, aiding in the traditional accounting of economic costs [17,18,19]. Despite these remarkable advantages of BIM, the environmental cost analysis of prefabricated buildings lacks an effective 5D BIM coding system to incorporate spatial and temporal dimensions.

Therefore, this study develops a 5D BIM-based framework to monetize environmental impacts into environmental costs in the construction process of prefabricated buildings, aiming to address the aforementioned issues. The innovations and significance of this study are as follows:

• Monetizing environmental impacts into environmental costs: By introducing environmental economics theories, environmental impacts are quantified as monetary environmental costs. This monetization approach standardizes environmental impacts by a unified measure, which offers an intuitive indicator for stakeholders.
• Introducing 5D BIM technology for environmental cost analysis: This study extends the application of 5D BIM from conventional economic costs to environmental costs. This new tool also presents spatial and temporal changes in terms of environmental costs.

2. Literature Review

2.1. Environmental Impacts of Prefabricated Buildings

In recent years, some research has advanced in the environmental impact assessment of prefabricated buildings, as shown in Table 1. Among these studies, life cycle assessment (LCA) is the most prevalent methodology [12,16,20]. According to ISO 14040 [21], LCA comprises four steps: (1) goal and scope definition; (2) inventory analysis; (3) impact assessment; (4) interpretation. Numerous studies focused on comparing the environmental performance of prefabricated buildings with conventional buildings [10,11,12,13]. Wang & Sinha also explored the environmental impacts under different prefabrication rates [14]. On this basis, scenario analysis was used to simulate their environmental impacts under different circumstances [22], while sensitivity analysis focused on the changes in input parameters on environmental impact results [23]. Additionally, the introduction of BIM has provided a more efficient and accurate tool for environmental impact assessment [7].

In these studies, the involved environmental indicators are diverse, including climate change potential (CCP), acidification potential (AP), eutrophication potential (EP), and so on. In terms of building types, the research involves residential buildings [14,16,20], school buildings [10], commercial buildings [22], office buildings [13], hospital buildings [6,24], and industrial buildings [23]. Geographically, these studies cover multiple countries, such as the United States [11,22], China [7,20], Italy [15,23], Spain [10], Germany [25], Sweden [14], Denmark [5], Malaysia [16], and Sri Lanka [13,24].

Table 1. Key studies on the environmental impacts of prefabricated buildings.

Focus	Environmental Indicator	Building Type	Region	Ref.
Comparing prefabricated and non-prefabricated technology	Materials weight, PED, CCP, ET, HT, material intensity, WRD, solid waste, recycled material, recyclable material	Prefabricated school building	Catalonia, Spain	[10]
Scenario analysis	EcoIndicator99, CCP	Prefabricated commercial building	San Francisco, California, USA	[22]
Comparing modular and conventional building	CCP, AP, carcinogens HT, non-cancer HT, criteria pollutants, EP, ET, POF, WRD, ODP	Modular homes	The United States	[11]
Sensitivity of input parameters	CCP, PED	Prefabricated industrial buildings	Italian	[23]
Input and output flows on factory level	CCP, ODP, AP, EP, PMF, ADP, renewable PED, non-renewable PED	Prefabricated timber houses	Germany	[25]
Energy performances by non-steady state simulation	CCP, ODP, AP, EP, POF, ADP, PED	Prefabricated simply temporary housing	Messina, Italy	[15]
Comparing modular and conventional methods by analytic hierarchy process	CCP, AP, human health, EP, PFM, ODP, PED, ET	Modular homes	Okanagan, British Columbia, Canada	[12]
Comparing concrete and steel prefabricated prefinished volumetric construction	CCP, non-renewable PED, PMF, LO, ADP	Prefabricated residential building	Malaysia	[16]
Automated building information modeling approach	ADP, AP, EP, freshwater ET, CCP, HT, marine ET, ODP, POF, terrestrial ET, renewable PED, non-renewable PED	Modular high-rise buildings	Hong Kong, China	[7]
Comparing different prefabricated rates	CCP, ODP, IR, ODP, human health, PFM, ODP, terrestrial ecosystems, terrestrial AP, freshwater EP, marine EP, terrestrial ET, freshwater ET, marine ET, carcinogenic ET, non-carcinogenic ET, LO, ADP, PED, WRD	Prefabricated residential building	Stockholm royal seaport, Sweden	[14]
Comparing different geographical contexts in absolute measures	CCP, ODP, EP, PDF, freshwater ET	Modular buildings	Australia and Denmark	[5]
Cradle-to-cradle for recyclability plan	Human health, ecosystem, CCP, resources	Modular residential building	Changsha, China	[20]
Comparing prefabricated and conventional construction	CCP, terrestrial AP, freshwater EP, marine EP, PMF, HT, freshwater ET, marine ET, PED	Prefabricated office building	Sri Lanka	[13]
Circular economy strategies	CCP, terrestrial AP, freshwater EP, HT, POF, PMF, terrestrial ET, freshwater ET, marine ET, agricultural LO, ADP, PED	Modular infectious disease building	Sri Lankan	[24]
Comparing prefabricated volumetric modular buildings with seismic-resistant	Agricultural LO, CCP, PED, freshwater ET, freshwater EP, HT, IR, marine ET, marine EP, ADP, natural soil transformation, ODP, PMF, POF, terrestrial AP, terrestrial ET, urban LO, WRD	Outpatient hospital building	Quito, Ecuador	[6]

Table 1. Key studies on the environmental impacts of prefabricated buildings.

Focus	Environmental Indicator	Building Type	Region	Ref.
Comparing prefabricated and non-prefabricated technology	Materials weight, PED, CCP, ET, HT, material intensity, WRD, solid waste, recycled material, recyclable material	Prefabricated school building	Catalonia, Spain	[10]
Scenario analysis	EcoIndicator99, CCP	Prefabricated commercial building	San Francisco, California, USA	[22]
Comparing modular and conventional building	CCP, AP, carcinogens HT, non-cancer HT, criteria pollutants, EP, ET, POF, WRD, ODP	Modular homes	The United States	[11]
Sensitivity of input parameters	CCP, PED	Prefabricated industrial buildings	Italian	[23]
Input and output flows on factory level	CCP, ODP, AP, EP, PMF, ADP, renewable PED, non-renewable PED	Prefabricated timber houses	Germany	[25]
Energy performances by non-steady state simulation	CCP, ODP, AP, EP, POF, ADP, PED	Prefabricated simply temporary housing	Messina, Italy	[15]
Comparing modular and conventional methods by analytic hierarchy process	CCP, AP, human health, EP, PFM, ODP, PED, ET	Modular homes	Okanagan, British Columbia, Canada	[12]
Comparing concrete and steel prefabricated prefinished volumetric construction	CCP, non-renewable PED, PMF, LO, ADP	Prefabricated residential building	Malaysia	[16]
Automated building information modeling approach	ADP, AP, EP, freshwater ET, CCP, HT, marine ET, ODP, POF, terrestrial ET, renewable PED, non-renewable PED	Modular high-rise buildings	Hong Kong, China	[7]
Comparing different prefabricated rates	CCP, ODP, IR, ODP, human health, PFM, ODP, terrestrial ecosystems, terrestrial AP, freshwater EP, marine EP, terrestrial ET, freshwater ET, marine ET, carcinogenic ET, non-carcinogenic ET, LO, ADP, PED, WRD	Prefabricated residential building	Stockholm royal seaport, Sweden	[14]
Comparing different geographical contexts in absolute measures	CCP, ODP, EP, PDF, freshwater ET	Modular buildings	Australia and Denmark	[5]
Cradle-to-cradle for recyclability plan	Human health, ecosystem, CCP, resources	Modular residential building	Changsha, China	[20]
Comparing prefabricated and conventional construction	CCP, terrestrial AP, freshwater EP, marine EP, PMF, HT, freshwater ET, marine ET, PED	Prefabricated office building	Sri Lanka	[13]
Circular economy strategies	CCP, terrestrial AP, freshwater EP, HT, POF, PMF, terrestrial ET, freshwater ET, marine ET, agricultural LO, ADP, PED	Modular infectious disease building	Sri Lankan	[24]
Comparing prefabricated volumetric modular buildings with seismic-resistant	Agricultural LO, CCP, PED, freshwater ET, freshwater EP, HT, IR, marine ET, marine EP, ADP, natural soil transformation, ODP, PMF, POF, terrestrial AP, terrestrial ET, urban LO, WRD	Outpatient hospital building	Quito, Ecuador	[6]

However, current research on prefabricated buildings remains at the level of environmental impact assessment. The units of these environmental impacts vary; for example, CCP is measured in kgCO₂ [12,15], PED in MJ [16], and PMF in kgPM10 [13]. This disparity in units makes it impossible to standardize different environmental impacts to a common benchmark. Moreover, without monetizing these indicators, it is challenging for stakeholders in prefabricated building projects to understand the negative economic effects of environmental impacts.

2.2. From 5D BIM to nD BIM

BIM (building information modeling) is a digital tool that conveys information across the building lifecycle [26,27]. As shown in

Table 2. Concepts and applications from 3D BIM to nD BIM.

Concept	Dimension	Application	Ref.
3D	Geometry	Visualization	[28,29]
		Clash detection	[30]
4D	Time	Schedule simulation	[29,30,31]
		Progress tracking	[32]
5D	Cost	Quantity surveying	[17,18,19,30,31,33,34]
		Life cycle costing	[35]
		Financial decision making	[36,37]
		Cost monitoring and payment	[19,32]
nD	Quality	Quality management	[38]
	Safety	Safety management	[38,39]
	Energy	Energy efficiency	[40,41,42]
	Carbon emission	Carbon emission calculation	[31,38]

, BIM has gradually expanded from the initial 3D model to 4D, 5D, and even nD, which incorporates more dimensions to achieve more efficient project management.

Three-dimensional BIM is essentially a geometric and spatial model [43] which captures the geometric information and spatial relationships of buildings [44,45]. The visual design of 3D BIM intuitively displays the overall facade and internal structure of buildings, offering relevant personnel a clearer understanding [28]. Additionally, its collision detection function can automatically check for conflicts between different professional models, such as pipes passing through beams, to identify and resolve design contradictions in advance [30].

Four-dimensional BIM introduces the time dimension based on 3D BIM and is mainly used for construction schedule management [46]. On the one hand, 4D BIM can simulate the construction sequences [29,30,31], such as the order of earthwork excavation, structure construction, and decoration. On the other hand, it can be used for progress tracking, comparing the planned schedule with the actual progress to identify potential delay risks and take corresponding adjustment measures [32].

Five-dimensional BIM further adds the cost dimension, integrating cost information with the 4D model for quantity surveying and cost management [47]. Specific functions include (1) quantity surveying: It extracts bills of quantities based on BIM [17,18,19,30,31,33,34]; (2) life cycle costing: It generates cost reports for different life cycle stages [35]; (3) financial decision making: It assesses the project’s feasibility by analyzing the life cycle cash flow [36,37]; and (4) cost monitoring and payment: Automated adjustment of payments in response to design alterations ensures precise cost control [19,32].

nD BIM introduces more dimensions based on 5D BIM. However, the industry has not yet agreed on which specific dimensions should be included [31,38]. Common extended dimensions are as follows: (1) Quality management: Associating quality standards with the BIM model to facilitate inspection and feedback during construction [38]. (2) Safety management: Using BIM to simulate construction safety hazards and proposing protective measures and emergency plans accordingly [38]. (3) Energy efficiency: Using BIM to simulate and analyze energy consumption and optimize energy performance [40,41]. (4) Carbon emission calculation: Calculating carbon emissions and selecting carbon reduction solutions [31,38].

Starting from the initial 3D, BIM has gradually expanded to 4D, 5D, and nD. Each expansion has brought new transformations and improvements to construction project management. In existing research, the extended dimensions of nD BIM, such as quality management, safety management, energy efficiency, and carbon emissions, have enriched the application value of the BIM model from different perspectives.

However, no research has considered environmental costs as part of the cost dimension of 5D BIM or as an extended dimension of nD BIM. Conventional 5D BIM mainly focuses on quantity surveying, emphasizing the accurate accounting of economic costs. In contrast, integrating environmental costs into it can combine economic and environmental costs, which is significant for a more comprehensive cost assessment in construction projects.

3. Method and Materials

Based on ISO 14040 [21] and ISO 14008 [48], this study proposes a method using 5D BIM to monetize the environmental impacts of the prefabricated substation into environmental costs during the construction process. The framework of this method consists of the following four steps: (1) Boundary definition: This includes defining the spatial boundary, temporal boundary, and environmental indicators. (2) Inventory acquisition: The resource inventory is automatically obtained using the coding system of 5D BIM. (3) Environmental impact assessment: The environmental impact results are obtained by multiplying the resource inventory by the environmental impact factors. (4) Environmental cost assessment: The environmental impacts are converted into environmental costs through the willingness-to-pay approach.

3.1. Boundary Definition

The boundary definition is divided into spatial and temporal scope boundaries, as shown in Figure 1.

The spatial scope encompasses all components that make up the prefabricated building, including the following: (1) Prefabricated wall (PW), (2) Prefabricated column (PC), (3) Prefabricated beam (PB), (4) Prefabricated slab (PS), (5) Prefabricated beam-slab (PBS), (6) Prefabricated foundation (PF) and so on.

The temporal boundary is defined as “cradle-to-site,” which includes five stages from material production to on-site assembly. This division is carried out by ISO 21931-1 [49], and the specific meanings of these stages are as follows: (1) Material production (MP): Extracting raw materials from nature and processing them into building materials; (2) Material transportation (MT): Transporting materials from their production site to a manufacturing factory; (3) Component prefabrication (CM): Producing prefabricated components in a prefabricated factory; (4) Component transportation (CT): Transporting components from a manufacturing factory to a construction site; (5) On-site assembly (OA): Pouring, assembling, and constructing components at a construction site.

In addition, the selection of environmental impact indicators is also crucial. Based on the recommendations of the China Life Cycle Database (CLCD) [50], these indicators include nine categories: climate change potential (CCP), primary energy demand (PED), abiotic depletion potential (ADP), water resource depletion (WRD), acidification potential (AP), eutrophication potential (EP), particulate matter formation (PMF), ozone depletion potential (ODP), photochemical ozone formation (POF).

3.2. Inventory Acquisition

The resource inventory is a detailed list that records all resources required for a construction project, covering the quantities of materials, energy, and machinery [43,44]. This study develops a 5D BIM method for automating resource inventory acquisition, achieving efficient data collection through a multi-software collaborative workflow. The specific technical route is as follows:

• Structural model creation: The YJK structural design software (YJK-A) [51] was used to build an accurate structural BIM model. When setting material parameters, key attributes such as concrete strength grade (e.g., C30/C35) and steel bar type (e.g., HRB400) were included.
• Architectural model supplementation: The YJK model was imported into Autodesk Revit 2018 [52] to supplement the architectural information of buildings.
• Detailed design model development: BeePC V4.2 [53] was used to add details of prefabricated components and their connection nodes (such as grouting sleeves and embedded parts).
• Resource inventory acquisition: BeePC software [53] can automatically collect and summarize resource data according to preset programs and rules, and then export the resource inventory for construction projects.

In the technical route, this study establishes a 5D BIM coding system for prefabricated building components (Figure 2). This coding system is used for data transmission in the above-mentioned technical route, which also facilitates the temporal and spatial analysis of environmental costs. The system uses a four-level mixed coding of English letters and Arabic numerals to achieve precise one-to-one coding for each component. Each level of coding is separated by a “.” (dot), while the sequence code is separated by a “-” (dash) within each level, such as UA.PB-01.OA-001.SE61-001.

• System classification code: The first-level code inherits the building structure system from GB/T 51061-2014 [54], which enables the identification of power grid projects. In this standard, “U” represents the building part of the power grid system, and “UA” denotes the civil engineering part of substations.
• Space dimension (3D) code: The second-level code inherits the IFC standard of buildingSmart [55]. This code represents the 3D information in the BIM model, namely the solid geometric information of components, which demonstrates the spatial dimension of the construction project, as shown in

  Table 3. Three-dimensional BIM coding of components for spatial dimension.

  Coding	Name	IFC Entity
  PW	Prefabricated wall	lfcWall
  PC	Prefabricated column	lfcColumn
  PB	Prefabricated beam	lfcBeam
  PS	Prefabricated slab	lfcSlab
  PBS	Prefabricated beam-slab	IfcBuildingElementProxy
  PF	Prefabricated foundation	IfcFooting

  . Notably, Table 3 only shows the six types of prefabricated components involved in this study. Other entities, such as IfcChimney, IfcStairFlight, and IfcRoof, can be supplemented according to actual needs.

3.

Time dimension (4D) code: The third-level code is divided according to the construction stages. Based on the stage code, a serial number can be assigned sequentially to represent the construction sequence of components. As shown in

Table 4. Four-dimensional BIM coding of components for temporal dimension.

Coding	Name	Meaning
MP	Material production	Extracting raw materials from nature and processing them into building materials.
MT	Material transportation	Transporting materials from the production site to the manufacturing factory.
CM	Component manufacturing	Processing materials into prefabricated components in the manufacturing factory.
CT	Component transportation	Transporting components from the manufacturing factory to the construction site.
OA	On-site assembly	Assembling and constructing components at the construction site.

, this code demonstrates the time dimension.

4.

Environmental cost (5D) code: The fourth-level code inherits the requirements of DL/T 5341-2021 [56]. As presented in

Table 5. Five-dimensional BIM coding of components for environmental costs.

Coding	Name	Characteristics	Unit
	Partial precast concrete components in the main structure are designed as cast-in-place.
SE46	Rectangular column	1. Concrete strength grade; 2. Concrete type; 3. Transportation distance	m3
SE47	Structural bracket		m3
SE48	Rectangular beam		m3
SE49	Lintel beam	1. Concrete strength grade; 2. Concrete type; 3. Production or purchase; 4. Transportation distance	m3
SE50	Crane beam		m3
SE51	Thin-web beam		m3
SE52	Light-aggregate concrete wall panel		m3
SE53	Slab	1. Concrete strength grade; 2. Concrete type; 3. Slab form; 4. Production or purchase; 5. Transportation distance	m3
SE54	Trench cover slab	1. Concrete strength grade; 2. Concrete type; 3. Transportation distance	m3
SE55	Angle steel framed concrete cover slab		m3
SE56	Small-sized component	1. Component name; 2. Concrete strength grade; 3. Concrete type; 4. Transportation distance	m3
SE57	Prestressed concrete slab	1. Concrete strength grade; 2. Concrete type; 3. Slab form; 4. Transportation distance	m3
SE58	Prestressed concrete crane beam	1. Concrete strength grade; 2. Concrete type; 3. Transportation distance	m3
	Precast concrete components in the main structure are designed as monolithic prefabricated units
SE59	Precast concrete foundation	1. Component name; 2. Concrete strength grade	m3
SE60	Precast concrete column		m3
SE61	Precast concrete beam		m3
SE62	Precast concrete slab		m3
SE63	Precast concrete air conditioning slab		m3
SE64	Precast concrete wall panel		m3
SE65	Precast concrete parapet wall		m3
SE66	Precast concrete coping		m3
SE67	Precast concrete column cap		m3
SE68	Precast concrete cable trench		m3
SE69	Precast concrete water tank		m3
SE70	Precast concrete fence panel		m3
SE71	Precast firewall		m3
SE72	Steel truss composite floor slab		m2
SE73	Precast cover plate		m2
SE74	Fiberglass grille	1. Material	m2
SE75	Aluminum-magnesium-manganese parapet coping		m

, this four-digit code serves as a quota code initially employed for quantity surveying in power transformer projects. This quota code mainly emphasizes the resource consumption of prefabricated components. Specifically, it not only records the characteristics of resources but also provides the resource quantity of each unit component. By applying the corresponding quota, the resource inventory of components can be obtained, thus providing a basis for calculating environmental impacts and environmental costs.

Actually, this four-digit code is recommended for economic cost measurement in Chinese power projects [56]. In this study, it is applied to calculating environmental costs, enabling a more comprehensive assessment of environmental impacts.

3.3. Environmental Impact Assessment

After getting the resource inventory, the next step is to multiply resource quantities by corresponding environmental impact factors to obtain the environmental impact results (Equation (1)).

$$\begin{array}{c}EI=\sum \left(EIF\times Q\right)\end{array}$$

(1)

In Equation (1), Q represents the resource quantity of the resource inventory, which is derived from the BIM. $EIF$ represents environmental impacts per unit of each resource.

Table 6. Environmental impact factors of main resources.

Name	Unit	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
		kgCO2eq	MJ	kgSbeq	kg	kgSO2eq	kgPO43−eq	kgPM2.5eq	kgCFC-11eq	kgNMVOCeq
Electricity	kWh	7.4 × 10−1	1.0 × 101	4.7 × 10−7	2.8	3.9 × 10−3	2.5 × 10−4	1.2 × 10−3	3.4 × 10−9	3.0 × 10−4
Diesel	t	7.9 × 102	4.7 × 104	1.7 × 10−2	4.1 × 103	3.8	5.8 × 10−1	6.0 × 10−1	4.2 × 10−4	3.1
Water	t	1.9 × 10−1	2.5	1.8 × 10−7	1.0 × 103	1.0 × 10−3	1.0 × 10−4	3.1 × 10−4	4.2 × 10−10	7.6 × 10−5
Hot-rolled steel bar	t	2.6 × 103	3.9 × 104	2.9 × 10−2	1.8 × 104	1.1 × 101	1.0	6.5	2.4 × 10−5	3.9
Ironware	t	2.4 × 103	2.9 × 104	4.1 × 10−3	1.2 × 104	8.2	8.1 × 10−1	7.6	2.0 × 10−5	3.2
Wire rope	t	2.3 × 103	3.4 × 104	2.8 × 10−2	1.6 × 104	9.5	9.2 × 10−1	5.8	2.3 × 10−5	3.6
Embedded iron part	t	2.4 × 103	2.9 × 104	4.1 × 10−3	1.2 × 104	8.2	8.1 × 10−1	7.7	2.0 × 10−5	3.2
Cement	t	5.7 × 10−2	7.9 × 10−1	2.5 × 10−6	1.2	2.1 × 10−4	1.2 × 10−4	6.8 × 10−5	1.1 × 10−9	5.5 × 10−5
Concrete C30	m3	3.2 × 102	2.3 × 103	2.3 × 10−4	6.7 × 102	8.7 × 10−1	1.1 × 10−1	3.2 × 10−1	3.8 × 10−6	5.0 × 10−1
Concrete C40	m3	3.6 × 102	2.5 × 103	2.4 × 10−4	7.1 × 102	9.5 × 10−1	1.2 × 10−1	3.6 × 10−1	3.8 × 10−6	5.6 × 10−1
Concrete C50	m3	4.0 × 102	2.8 × 103	2.5 × 10−4	7.6 × 102	1.0	1.3 × 10−1	3.9 × 10−1	3.8 × 10−6	6.2 × 10−1
Dry-mixed mortar	m3	3.2 × 102	2.3 × 103	2.3 × 10−4	6.7 × 102	8.7 × 10−1	1.1 × 10−1	3.2 × 10−1	3.8 × 10−6	5.0 × 10−1
Foamed ceramic	m3	6.6 × 102	1.4 × 103	3.5 × 10−3	5.6 × 102	1.1	1.5 × 10−1	1.9 × 10−1	4.2 × 10−7	4.4 × 10−1

shows its main data, which are sourced from the Chinese Life Cycle Database (CLCD) [50]. This database is a popular LCA database in China with regularly updated resources. It encompasses the majority of resources in the construction industry and takes into account their specific production processes within the Chinese context.

3.4. Environmental Cost Assessment

After accurately calculating the environmental impacts, a subsequent step is to convert them into intuitive environmental costs. This conversion is achieved through the willingness-to-pay (WTP) method, which represents the monetary value that the public is willing to pay to avoid or reduce specific environmental damages [48]. Its calculation formula is shown in Equation (2).

$$\begin{array}{c}EC = WTP\times EI\end{array}$$

(2)

where EC stands for environmental costs, $EI$ represents environmental impacts, and $WTP$ denotes the monetary value by willingness-to-pay.

People in different regions may have different WTP due to variations in lifestyle, income level, environmental awareness, and other factors. When using the WTP method to monetize environmental impacts, these specific circumstances need to be fully taken into account. Therefore, this study adopts the WTP determined by Zhu et al. [57], Cao [58], and Li et al. [59] as the monetary values applicable to the actual situation in China. Although the studies were conducted some time ago, the relevant socioeconomic factors and people’s attitudes have not changed significantly, rendering these WTP values still applicable. Therefore, these parameters are more in line with China’s conditions, thus ensuring higher accuracy and reliability, as presented in

Table 7. Monetary values of environmental costs based on willingness-to-pay (WTP).

Environmental Indicator	Abbreviation	Unit	Monetary Value	Ref.
Climate change potential	CCP	CNY/kgCO2eq	0.28	[57]
Primary energy demand	PED	CNY/MJ	0.00028	[58]
Abiotic depletion potential	ADP	CNY/kgSbeq	0.0191	[59]
Water resource depletion	WRD	CNY/kg	0.00139	[57]
Acidification potential	AP	CNY/kgSO2eq	1.71	[57]
Eutrophication potential	EP	CNY/kgPO43−eq	0.73	[58]
Particulate matter formation	PMF	CNY/kgPM2.5eq	0.69	[57]
Ozone depletion potential	ODP	CNY/kgCFC-11eq	16.24	[57]
Photochemical ozone formation	POF	CNY/kgNMVOCeq	8.75	[57]

.

3.5. Case Study

After proposing this method, this study employs a prefabricated substation as a case study to validate its effectiveness. In fact, according to Chen et al.’s review [60], most studies about the environmental impacts of prefabricated buildings have focused on residential and office buildings, while research on industrial buildings, especially substations, is extremely scarce. Therefore, this substation project is selected to fill the gap for the environmental aspects of industrial buildings.

The substation building is located in Xiamen City, with a floor area of 1080 square meters. It is a one-story building, and its total height is 12.55 m. This project is an unattended distribution device building. Its corresponding BIM is presented in Figure 3, with detailed background information provided in

Table 8. Background information and parameters of the substation building in case study.

Item	Content
Building type	110 kV prefabricated substation
Building location	Xiamen, China
Construction company	State Grid Fujian Electric Power Co., Ltd.
Building area	1080 m2
Building floor	One floor
Building height	12.55 m
Functional layout	10 kV power distribution room, Main transformer room, Radiator room, 110 kV Gas Insulated Switchgear room, Secondary equipment room, Battery room, etc.
From concrete plant to prefabricated factory	35 km
From steel plant to prefabricated factory	30 km
From foam ceramic plant to prefabricated factory	40 km
From prefabricated factory to construction site	125 km

.

After calculating the environmental impacts and environmental costs of the case building, this study analyzes the results from two aspects, i.e., the space dimension and the time dimension. It examines the proportion attributed to each dimension and identifies factors that significantly influence the results.

4. Environmental Impact Results

Through the above calculations, the environmental impacts of the case study are as follows: CCP: 607,974.11 kgCO₂eq, PED: 7,336,871.26 MJ, ADP: 3.57 kgSbeq, WRD: 2,002,933.13 kg, AP: 1874.12 kgSO₂eq, EP: 215.32 kgPO₄³⁻eq, PMF: 745.79 kgPM2.5eq, ODP: 0.03 kgCFC-11eq, POF: 882.26 kgNMVOCeq. Their detailed calculation processes can be found in

Table A1. Environmental impacts of prefabricated walls.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				kgCO2eq	MJ	kgSbeq	kg	kgSO2eq	kgPO43−eq	kgPM2.5eq	kgCFC-11eq	kgNMVOCeq
MP	Concrete C40	m3	226.608	82,075.69	574,649.05	0.05	161,695.56	214.17	27.90	80.49	0.001	127.33
	Foamed ceramics	m3	216.192	141,605.76	309,262.66	0.76	120,527.04	246.24	31.46	40.27	0.000	94.87
MT	Diesel for transporting Concrete	t	3.724	2941.59	175,006.26	0.06	15,142.39	14.27	2.15	2.25	0.002	11.54
	Diesel for transporting foamed ceramics	t	1.671	1319.88	78,524.39	0.03	6794.31	6.40	0.96	1.01	0.001	5.18
CM	Electricity	kWh	19,925.978	14,725.30	207,230.17	0.01	55,394.22	77.91	5.04	22.91	0.000	6.00
	Binding wire	t	0.155	358.48	5202.97	0.00	2508.58	1.47	0.14	0.90	0.000	0.56
CT	Diesel for component transportation	t	18.519	14,630.31	870,411.08	0.31	75,312.16	70.99	10.68	11.17	0.008	57.41
OA	Dry-mixed mortar DMM20	m3	3.542	1141.57	8131.76	0.00	2369.16	3.08	0.40	1.14	0.000	1.78
	Shimming iron parts	t	0.909	2145.38	26,362.74	0.00	10,508.73	7.45	0.74	6.95	0.000	2.89
	Grouting material for C40	m3	7.289	2639.98	18,483.71	0.00	5200.97	6.89	0.90	2.59	0.000	4.10
	Diesel for construction machinery	t	1.039	820.97	48,842.27	0.02	4226.07	3.98	0.60	0.63	0.000	3.22
Total				264,404.92	2,322,107.06	1.25	459,679.18	652.87	80.97	170.30	0.012	314.88

,

Table A2. Environmental impacts of prefabricated columns.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				kgCO2eq	MJ	kgSbeq	kg	kgSO2eq	kgPO43−eq	kgPM2.5eq	kgCFC-11eq	kgNMVOCeq
MP	Concrete C40	m3	90.41	32,745.52	229,266.22	0.02	64,511.25	85.45	11.13	32.11	0.000	50.80
	Reinforcing steel bars	t	23.11	60,930.92	903,458.54	0.67	420,213.27	252.39	23.72	151.01	0.001	89.82
MT	Diesel for transporting Concrete	t	1.49	1173.60	69,821.79	0.02	6041.32	5.69	0.86	0.90	0.001	4.61
	Diesel for transporting reinforcing steel bars	t	0.13	105.82	6295.91	0.00	544.75	0.51	0.08	0.08	0.000	0.42
CM	Electricity	kWh	4520.45	3340.61	47,012.68	0.00	12,566.85	17.67	1.14	5.20	0.000	1.36
	Binding wires	t	0.23112	535.04	7765.63	0.01	3744.14	2.20	0.21	1.34	0.000	0.84
CT	Diesel for component transportation	t	5.86	4632.37	275,596.50	0.10	23,845.94	22.48	3.38	3.54	0.002	18.18
OA	Dry-mixed mortar DMM20	m3	0.72	233.08	1660.31	0.00	483.72	0.63	0.08	0.23	0.000	0.36
	Shimming iron parts	t	0.19	438.04	5382.68	0.00	2145.65	1.52	0.15	1.42	0.000	0.59
	Grouting material for C40	m3	1.49	539.02	3773.93	0.00	1061.91	1.41	0.18	0.53	0.000	0.84
	Diesel for construction machinery	t	0.33	260.55	15,501.17	0.01	1341.24	1.26	0.19	0.20	0.000	1.02
Total				104,934.59	1,565,535.35	0.83	536,500.05	391.22	41.13	196.56	0.004	168.83

,

Table A3. Environmental impacts of prefabricated beams.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				kgCO2eq	MJ	kgSbeq	kg	kgSO2eq	kgPO43−eq	kgPM2.5eq	kgCFC-11eq	kgNMVOCeq
MP	Concrete C40	m3	41.26	14,945.68	104,641.50	0.01	29,444.17	39.00	5.08	14.66	0.000	23.19
	Reinforcing steel bars	t	8.52	22,458.81	333,009.98	0.25	154,888.36	93.03	8.74	55.66	0.000	33.11
MT	Diesel for transporting Concrete	t	0.68	535.65	31,868.00	0.01	2757.37	2.60	0.39	0.41	0.000	2.10
	Diesel for transporting reinforcing steel bars	t	0.05	39.01	2320.64	0.00	200.79	0.19	0.03	0.03	0.000	0.15
CM	Electricity	kWh	2475.86	1829.66	25,748.99	0.00	6882.90	9.68	0.63	2.85	0.000	0.75
	Binding wires	t	0.09	197.21	2862.38	0.00	1380.08	0.81	0.08	0.49	0.000	0.31
CT	Diesel for component transportation	t	2.63	2075.58	123,483.62	0.04	10,684.40	10.07	1.52	1.59	0.001	8.14
OA	Shimming iron parts	t	0.05	129.23	1587.98	0.00	633.00	0.45	0.04	0.42	0.000	0.17
	Grouting material for C40	m3	0.75	270.62	1894.74	0.00	533.15	0.71	0.09	0.27	0.000	0.42
	Diesel for construction machinery	t	0.22	177.18	10,540.79	0.00	912.04	0.86	0.13	0.14	0.000	0.70
Total				42,658.64	637,958.63	0.32	208,316.27	157.39	16.73	76.50	0.002	69.04

,

Table A4. Environmental impacts of prefabricated slabs.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				kgCO2eq	MJ	kgSbeq	kg	kgSO2eq	kgPO43−eq	kgPM2.5eq	kgCFC-11eq	kgNMVOCeq
MP	Concrete C40	m3	11.6422	4216.73	29,523.20	0.00	8307.28	11.00	1.43	4.14	0.000	6.54
	Reinforcing steel bars	t	1.84	4841.23	71,783.81	0.05	33,387.82	20.05	1.88	12.00	0.000	7.14
MT	Diesel for transporting Concrete	t	0.19	151.13	8991.13	0.00	777.96	0.73	0.11	0.12	0.000	0.59
	Diesel for transporting reinforcing steel bars	t	0.01	8.41	500.24	0.00	43.28	0.04	0.01	0.01	0.000	0.03
CM	Electricity	kWh	523.90	387.16	5448.55	0.00	1456.44	2.05	0.13	0.60	0.000	0.16
	Binding wires	t	0.02	42.50	616.90	0.00	297.43	0.17	0.02	0.11	0.000	0.07
CT	Diesel for component transportation	t	0.73	574.78	34,195.51	0.01	2958.76	2.79	0.42	0.44	0.000	2.26
OA	Post-cast Concrete C40	m3	11.293	4090.22	28,637.51	0.00	8058.06	10.67	1.39	4.01	0.000	6.35
	Shimming iron parts	t	0.101	237.39	2917.07	0.00	1162.80	0.82	0.08	0.77	0.000	0.32
	Grouting material for C40	m3	0.24	86.76	607.47	0.00	170.93	0.23	0.03	0.09	0.000	0.13
	Diesel for construction machinery	t	0.61	480.93	28,612.22	0.01	2475.67	2.33	0.35	0.37	0.000	1.89
Total				15,117.24	211,833.61	0.09	59,096.43	50.90	5.86	22.64	0.001	25.47

,

Table A5. Environmental impacts of prefabricated beam-slabs.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				kgCO2eq	MJ	kgSbeq	kg	kgSO2eq	kgPO43−eq	kgPM2.5eq	kgCFC-11eq	kgNMVOCeq
MP	Concrete C40	m3	114.02	41,295.56	289,128.93	0.03	81,355.50	107.76	14.04	40.50	0.000	64.06
	Reinforcing steel bars	t	14.77	38,944.52	577,453.25	0.43	268,582.91	161.32	15.16	96.52	0.000	57.41
MT	Diesel for transporting Concrete	t	1.87	1480.03	88,052.65	0.03	7618.74	7.18	1.08	1.13	0.001	5.81
	Diesel for transporting reinforcing steel bars	t	0.09	67.64	4024.09	0.00	348.18	0.33	0.05	0.05	0.000	0.27
CM	Electricity	kWh	5130.69	3791.58	53,359.16	0.00	14,263.31	20.06	1.30	5.90	0.000	1.54
	Binding wires	t	0.15	341.97	4963.39	0.00	2393.06	1.40	0.14	0.86	0.000	0.54
CT	Diesel for component transportation	t	7.05	5567.66	331,240.78	0.12	28,660.55	27.02	4.06	4.25	0.003	21.85
OA	Post-cast Concrete C40	m3	102.61	37,166.01	260,216.04	0.02	73,219.95	96.98	12.64	36.45	0.000	57.66
	Shimming iron parts	t	0.99	2324.82	28,567.67	0.00	11,387.67	8.08	0.80	7.53	0.000	3.13
	Grouting material C40	m3	2.35	849.70	5949.15	0.00	1673.98	2.22	0.29	0.83	0.000	1.32
	Diesel for construction machinery	t	5.96	4709.87	280,207.42	0.10	24,244.90	22.85	3.44	3.60	0.003	18.48
Total				136,539.37	1,923,162.54	0.74	513,748.76	455.20	52.99	197.62	0.008	232.07

and

Table A6. Environmental impacts of prefabricated foundations.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				kgCO2eq	MJ	kgSbeq	kg	kgSO2eq	kgPO43−eq	kgPM2.5eq	kgCFC-11eq	kgNMVOCeq
MP	Concrete C30	m3	43.8120	14,148.13	100,616.19	0.01	29,305.69	38.10	5.00	14.13	0.000	21.98
	Reinforcing steel bars	t	9.46	24,929.14	369,638.95	0.27	171,925.09	103.26	9.70	61.79	0.000	36.75
MT	Diesel for transporting Concrete	t	0.71	557.02	33,139.28	0.01	2867.37	2.70	0.41	0.43	0.000	2.19
	Diesel for transporting reinforcing steel bars	t	0.05	43.30	2575.90	0.00	222.88	0.21	0.03	0.03	0.000	0.17
CM	Electricity	kWh	2190.60	1618.85	22,782.24	0.00	6089.87	8.57	0.55	2.52	0.000	0.66
	Binding wires	t	0.09	218.91	3177.22	0.00	1531.87	0.90	0.09	0.55	0.000	0.34
CT	Diesel for component transportation	t	2.75	2169.77	129,087.47	0.05	11,169.27	10.53	1.58	1.66	0.001	8.51
OA	Shimming iron parts	t	0.09	212.27	2608.44	0.00	1039.78	0.74	0.07	0.69	0.000	0.29
	Grouting material C30	m3	0.74	237.78	1691.03	0.00	492.53	0.64	0.08	0.24	0.000	0.37
	Diesel for construction machinery	t	0.23	184.18	10,957.39	0.00	948.09	0.89	0.13	0.14	0.000	0.72
Total				44,319.35	676,274.08	0.35	225,592.43	166.54	17.66	82.17	0.002	71.98

in the Appendix.

4.1. Space Dimension Analysis of Environmental Impacts

The spatial dimension analysis for the environmental impacts of the case building is shown in Figure 4. For the vast majority of environmental indicators, the prefabricated wall is the biggest contributor to environmental impacts, followed by prefabricated beam-slabs, which may be positively correlated with their huge volume. In addition, structural components such as columns, beams, and foundations also contribute a lot to environmental impacts. Since these components bear the main structural loads, their cumulative environmental impacts are also relatively high.

However, an exception is particulate matter formation (PMF). The main contributors of PMF are prefabricated beam-slabs (26.5%) and prefabricated columns (26.4%), followed by prefabricated walls (22.8%). The main reason is that the main material of prefabricated walls, foamed ceramics, has a relatively low PMF value, only 0.19 kgPM2.5eq/m³. A similar environmental indicator is water resource depletion (WRD). Its spatial composition is prefabricated columns (26.8%) > prefabricated beam-slabs (25.6%) > prefabricated walls (23.0%).

4.2. Time Dimension Analysis of Environmental Impacts

Figure 5 shows the distribution of environmental impacts in the time dimension. Except for ozone depletion potential (ODP), material production serves as the core stage for all other indicators, accounting for a proportion that spans from 53.1% to 80.9%. This indicates that material selection is the key during prefabricated construction.

As an exception, the composition proportion of ODP is as follows: component transportation (56.4%) > material transportation (16.0%) > material production (12.6%). The main reason is the extensive use of diesel in the transportation process, with its environmental impact factor for ODP is particularly high, reaching 4.2 × 10⁻⁴ kgCFC-11eq/t. This is significantly higher than other building materials, such as 2.4 × 10⁻⁵ kgCFC-11eq/t for steel bars and 1.1 × 10⁻⁹ kgCFC-11eq/t for cement. Such a disparity suggests that reducing diesel use is key to lowering ODP in prefabricated building construction.

5. Environmental Cost Results

Using the above method, the environmental costs of this prefabricated building are 186,638.63 CNY (172.81 CNY/m²). Detailed calculation processes can be found in

Table A7. Environmental costs of prefabricated walls.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY
MP	Concrete—C40	m3	226.608	22,981.19	158.60	0.00	224.76	366.23	20.37	55.54	0.01	1114.13
	Foamed ceramics	m3	216.192	39,649.61	85.36	0.01	167.53	421.07	22.96	27.78	0.00	830.07
MT	Diesel for transporting Concrete	t	3.724	823.65	48.30	0.00	21.05	24.41	1.57	1.55	0.03	101.00
	Diesel for transporting foamed ceramics	t	1.671	369.57	21.67	0.00	9.44	10.95	0.70	0.70	0.01	45.32
CM	Electricity	kWh	19,925.978	4123.08	57.20	0.00	77.00	133.23	3.68	15.81	0.00	52.48
	Binding wire	t	0.155	100.37	1.44	0.00	3.49	2.52	0.10	0.62	0.00	4.92
CT	Diesel for component transportation	t	18.519	4096.49	240.23	0.01	104.68	121.39	7.80	7.71	0.13	502.34
OA	Dry-mixed mortar DMM20	m3	3.542	319.64	2.24	0.00	3.29	5.27	0.29	0.79	0.00	15.60
	Shimming iron parts	t	0.909	600.71	7.28	0.00	14.61	12.75	0.54	4.79	0.00	25.29
	Concrete grouting material—C40	m3	7.289	739.20	5.10	0.00	7.23	11.78	0.66	1.79	0.00	35.84
	Diesel for construction machinery	t	1.039	229.87	13.48	0.00	5.87	6.81	0.44	0.43	0.01	28.19
Total				74,033.38	640.90	0.02	638.95	1116.41	59.11	117.51	0.19	2755.17

,

Table A8. Environmental costs of prefabricated columns.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY
MP	Concrete C40	m3	90.41	9168.75	63.28	0.00	89.67	146.11	8.13	22.16	0.01	444.50
	Reinforcing steel bars	t	23.11	17,060.66	249.35	0.01	584.10	431.59	17.31	104.20	0.01	785.93
MT	Diesel for the transportation of Concrete	t	1.49	328.61	19.27	0.00	8.40	9.74	0.63	0.62	0.01	40.30
	Diesel for the transportation of reinforcing steel bars	t	0.13	29.63	1.74	0.00	0.76	0.88	0.06	0.06	0.00	3.63
CM	Electricity	kWh	4520.45	935.37	12.98	0.00	17.47	30.22	0.83	3.59	0.00	11.91
	Timber spacers	t	0.23112	149.81	2.14	0.00	5.20	3.75	0.16	0.92	0.00	7.34
CT	Diesel for component transportation	t	5.86	1297.06	76.06	0.00	33.15	38.44	2.47	2.44	0.04	159.05
OA	Dry-mixed mortar DMM20	m3	0.72	65.26	0.46	0.00	0.67	1.08	0.06	0.16	0.00	3.18
	Shimming iron parts	t	0.19	122.65	1.49	0.00	2.98	2.60	0.11	0.98	0.00	5.16
	Grouting material—C40	m3	1.49	150.93	1.04	0.00	1.48	2.41	0.13	0.36	0.00	7.32
	Diesel for construction machinery	t	0.33	72.95	4.28	0.00	1.86	2.16	0.14	0.14	0.00	8.95
Total				29,381.68	432.09	0.02	745.74	668.98	30.02	135.63	0.07	1477.28

,

Table A9. Environmental costs of prefabricated beams.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY
MP	Concrete C40	m3	41.26	4184.79	28.88	0.00	40.93	66.69	3.71	10.11	0.00	202.88
	Reinforcing steel bars	t	8.52	6288.47	91.91	0.00	215.29	159.08	6.38	38.41	0.00	289.69
MT	Diesel for transporting Concrete	t	0.68	149.98	8.80	0.00	3.83	4.44	0.29	0.28	0.00	18.39
	Diesel for transporting reinforcing steel bars	t	0.05	10.92	0.64	0.00	0.28	0.32	0.02	0.02	0.00	1.34
CM	Electricity	kWh	2475.86	512.31	7.11	0.00	9.57	16.55	0.46	1.96	0.00	6.52
	Binding wires	t	0.09	55.22	0.79	0.00	1.92	1.38	0.06	0.34	0.00	2.71
CT	Diesel for component transportation	t	2.63	581.16	34.08	0.00	14.85	17.22	1.11	1.09	0.02	71.27
OA	Shimming iron parts	t	0.05	36.18	0.44	0.00	0.88	0.77	0.03	0.29	0.00	1.52
	Grouting material—C40	m3	0.75	75.77	0.52	0.00	0.74	1.21	0.07	0.18	0.00	3.67
	Diesel for construction machinery	t	0.22	49.61	2.91	0.00	1.27	1.47	0.09	0.09	0.00	6.08
Total				11,944.42	176.08	0.01	289.56	269.14	12.21	52.79	0.03	604.07

,

Table A10. Environmental costs of prefabricated slabs.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY
MP	Concrete C40	m3	11.6422	1180.68	8.15	0.00	11.55	18.82	1.05	2.85	0.00	57.24
	Reinforcing steel bars	t	1.84	1355.55	19.81	0.00	46.41	34.29	1.38	8.28	0.00	62.45
MT	Diesel for transporting Concrete	t	0.19	42.32	2.48	0.00	1.08	1.25	0.08	0.08	0.00	5.19
	Diesel for transporting reinforcing steel bars	t	0.01	2.35	0.14	0.00	0.06	0.07	0.00	0.00	0.00	0.29
CM	Electricity	kWh	523.90	108.41	1.50	0.00	2.02	3.50	0.10	0.42	0.00	1.38
	Binding wires	t	0.02	11.90	0.17	0.00	0.41	0.30	0.01	0.07	0.00	0.58
CT	Diesel for component transportation	t	0.73	160.94	9.44	0.00	4.11	4.77	0.31	0.30	0.00	19.74
OA	Post-cast Concrete C40	m3	11.293	1145.26	7.90	0.00	11.20	18.25	1.02	2.77	0.00	55.52
	Shimming iron parts	t	0.101	66.47	0.81	0.00	1.62	1.41	0.06	0.53	0.00	2.80
	Grouting material—C40	m3	0.24	24.29	0.17	0.00	0.24	0.39	0.02	0.06	0.00	1.18
	Diesel for construction machinery	t	0.68	134.66	7.90	0.00	3.44	3.99	0.26	0.25	0.00	16.51
Total				4232.83	58.47	0.00	82.14	87.04	4.27	15.62	0.01	222.87

,

Table A11. Environmental costs of prefabricated beam-slabs.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY
MP	Concrete C40	m3	114.02	11,562.76	79.80	0.00	113.08	184.26	10.25	27.94	0.01	560.56
	Reinforcing steel bars	t	14.77	10,904.47	159.38	0.01	373.33	275.85	11.07	66.60	0.01	502.33
MT	Diesel for transporting Concrete	t	1.87	414.41	24.30	0.00	10.59	12.28	0.79	0.78	0.01	50.82
	Diesel for transporting reinforcing steel bars	t	0.09	18.94	1.11	0.00	0.48	0.56	0.04	0.04	0.00	2.32
CM	Electricity	kWh	5130.69	1061.64	14.73	0.00	19.83	34.30	0.95	4.07	0.00	13.51
	Binding wires	t	0.15	95.75	1.37	0.00	3.33	2.40	0.10	0.59	0.00	4.69
CT	Diesel for component transportation	t	7.05	1558.95	91.42	0.00	39.84	46.20	2.97	2.93	0.05	191.17
OA	Post-cast Concrete C40	m3	102.61	10,406.48	71.82	0.00	101.78	165.84	9.22	25.15	0.01	504.51
	Shimming iron parts	t	0.99	650.95	7.88	0.00	15.83	13.81	0.58	5.19	0.00	27.41
	Grouting material C40	m3	2.35	237.92	1.64	0.00	2.33	3.79	0.21	0.57	0.00	11.53
	Diesel for construction machinery	t	6.62	1318.76	77.34	0.00	33.70	39.08	2.51	2.48	0.04	161.72
Total				38,231.02	530.79	0.01	714.11	778.38	38.68	136.36	0.12	2030.58

and

Table A12. Environmental costs of prefabricated foundations.

Stage	Resource	Unit	Quantity	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
				CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY	CNY
MP	Concrete C30	m3	43.8120	3961.48	27.77	0.00	40.73	65.15	3.65	9.75	0.00	192.32
	Reinforcing steel bars	t	9.46	6980.16	102.02	0.01	238.98	176.58	7.08	42.63	0.00	321.55
MT	Diesel for transporting Concrete	t	0.71	155.97	9.15	0.00	3.99	4.62	0.30	0.29	0.00	19.13
	Diesel for transporting reinforcing steel bars	t	0.05	12.12	0.71	0.00	0.31	0.36	0.02	0.02	0.00	1.49
CM	Electricity	kWh	2190.60	453.28	6.29	0.00	8.46	14.65	0.40	1.74	0.00	5.77
	Binding wires	t	0.09	61.29	0.88	0.00	2.13	1.54	0.06	0.38	0.00	3.00
CT	Diesel for component transportation	t	2.75	607.54	35.63	0.00	15.53	18.00	1.16	1.14	0.02	74.50
OA	Shimming iron parts	t	0.09	59.44	0.72	0.00	1.45	1.26	0.05	0.47	0.00	2.50
	Grouting material C30	m3	0.74	66.58	0.47	0.00	0.68	1.09	0.06	0.16	0.00	3.23
	Diesel for construction machinery	t	0.23	51.57	3.02	0.00	1.32	1.53	0.10	0.10	0.00	6.32
Total				12,409.42	186.65	0.01	313.57	284.78	12.89	56.69	0.03	629.82

in the Appendix. The corresponding environmental costs for CCP, PED, ADP, WRD, AP, EP, PMF, ODP, and POF are 170,232.75 CNY (91.2%), 2024.98 CNY (1.1%), 0.07 CNY (0.0%), 2784.08 CNY (1.5%), 3204.74 CNY (1.7%), 157.19 CNY (0.1%), 514.59 CNY (0.3%), 0.45 CNY (0.0%), and 7719.79 CNY (4.1%), respectively. It is obvious that the CCP constitutes the most significant environmental cost (91.2%), followed by POF (4.1%).

5.1. Space Dimension Analysis of Environmental Costs

From the spatial dimension analysis (Figure 6), the environmental costs of prefabricated walls, columns, beams, slabs, beam-slabs, and foundations in the case building are 79,361.65 CNY, 32,871.50 CNY, 13,348.31 CNY, 4703.26 CNY, 42,460.06 CNY, and 13,893.86 CNY, respectively.

Among these components, the walls make the greatest contribution to environmental costs, accounting for 42.5%, followed by beam-slabs (22.7%). This contribution might be positively correlated with their volume proportion. It is worth noting that, as shown in Table A10 and Table A11, the beam-slabs and slabs require concrete pouring during the on-site assembly stage to form an integrated structure. Therefore, their on-site assembly accounts for 32.08% and 32.74% of the environmental costs, respectively. This indicates that more attention should be paid to these two components compared to other components in this stage. This phenomenon also represents the emission-reduction bottleneck in the wet-work processes of current prefabricated buildings.

In addition, load-bearing components, such as columns, beams, and foundations, also contribute to a large share of environmental costs, accounting for 17.6%, 7.2%, and 7.4%, respectively. Since these components bear the main structural loads, their environmental costs during material production are relatively high. Notably, even though the case building is a single-story structure, the environmental costs of foundations remain considerable (7.4%). This finding underscores the importance of considering environmental costs associated with foundations, even in single-story buildings.

5.2. Time Dimension Analysis of Environmental Costs

Figure 7 shows significant differences in the environmental cost contributions of each stage. Material production emerges as the core stage, with an environmental cost of 146,738.31 CNY (accounting for 78.6%). This is understandable because climate change potential (CCP) is the most important environmental indicator, accounting for 91.2% of environmental costs, so its distribution is very similar between environmental impacts and environmental costs.

In contrast, the environmental costs of other stages seem less significant. The costs for material transportation, component manufacturing, component transportation, and on-site assembly are 2925.15 CNY (1.6%), 8322.44 CNY (4.5%), 10,296.93 CNY (5.5%), and 18,355.80 CNY (9.8%), respectively. Interestingly, the on-site assembly accounts for the second highest proportion (9.8%), due to the need to pour concrete for slabs and beam-slabs, as well as grouting materials for component connections.

6. Discussion

6.1. Sensitivity Analysis

To further explore the impact of monetary values that monetize environmental impacts into environmental costs, this study conducts a sensitivity analysis of these monetary values, as shown in Figure 8 and

Table A13. Sensitivity analysis of monetary values on environmental costs: Absolute value.

CNY	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
−20%	152,592.1	186,233.6	186,638.6	186,081.8	185,997.7	186,607.2	186,535.7	186,638.5	185,094.7
−15%	161,103.7	186,334.9	186,638.6	186,221.0	186,157.9	186,615.1	186,561.4	186,638.6	185,480.7
−10%	169,615.4	186,436.1	186,638.6	186,360.2	186,318.2	186,622.9	186,587.2	186,638.6	185,866.7
−5%	178,127.0	186,537.4	186,638.6	186,499.4	186,478.4	186,630.8	186,612.9	186,638.6	186,252.6
0%	186,638.6	186,638.6	186,638.6	186,638.6	186,638.6	186,638.6	186,638.6	186,638.6	186,638.6
5%	195,150.3	186,739.9	186,638.6	186,777.8	186,798.9	186,646.5	186,664.4	186,638.7	187,024.6
10%	203,661.9	186,841.1	186,638.6	186,917.0	186,959.1	186,654.4	186,690.1	186,638.7	187,410.6
15%	212,173.5	186,942.4	186,638.6	187,056.2	187,119.3	186,662.2	186,715.8	186,638.7	187,796.6
20%	220,685.2	187,043.6	186,638.6	187,195.4	187,279.6	186,670.1	186,741.5	186,638.7	188,182.6

and

Table A14. Sensitivity analysis of monetary values on environmental costs: Relative percentage.

%	CCP	PED	ADP	WRD	AP	EP	PMF	ODP	POF
−20%	−18.24%	−0.22%	0.00%	−0.30%	−0.34%	−0.02%	−0.06%	0.00%	−0.83%
−15%	−13.68%	−0.16%	0.00%	−0.22%	−0.26%	−0.01%	−0.04%	0.00%	−0.62%
−10%	−9.12%	−0.11%	0.00%	−0.15%	−0.17%	−0.01%	−0.03%	0.00%	−0.41%
−5%	−4.56%	−0.05%	0.00%	−0.07%	−0.09%	0.00%	−0.01%	0.00%	−0.21%
0%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
5%	4.56%	0.05%	0.00%	0.07%	0.09%	0.00%	0.01%	0.00%	0.21%
10%	9.12%	0.11%	0.00%	0.15%	0.17%	0.01%	0.03%	0.00%	0.41%
15%	13.68%	0.16%	0.00%	0.22%	0.26%	0.01%	0.04%	0.00%	0.62%
20%	18.24%	0.22%	0.00%	0.30%	0.34%	0.02%	0.06%	0.00%	0.83%

.

The results indicate that the monetary value of climate change potential (CCP) has the most significant influence on environmental costs, ranging from −18.24% to 18.24%. This is because CCP accounts for a substantial proportion (91.2%) of the total environmental costs. In contrast, the monetary values of other environmental impacts contribute no more than 1%, suggesting that their effects are negligible. Through this sensitivity analysis, more attention should be focused on the changes in CCP when managing environmental costs.

6.2. Benefit of Monetizing Environmental Impacts

This study monetizes environmental impacts during prefabricated construction, converting them into environmental costs. Historically, environmental impact results using LCA [21] were presented in different units, such as CO₂ [12,15], Joule [16], and PM10 [13]. This proposed method overcomes this long-standing challenge of unit unification [61,62]. As a result, various environmental impacts can be measured by a single economic indicator, environmental costs, which facilitates their direct comparisons.

In practical applications, monetized environmental costs offer straightforward indicators for stakeholders in construction projects [63]. Previously, stakeholders often had a vague understanding of environmental impacts [8]. For instance, it is hard for them to comprehend the meaning of a CCP of 607,974.11 kgCO₂eq, but it is easy for them to understand the corresponding environmental costs of 170,232.75 CNY in this case study. Therefore, the method enables engineers to convey the environmental impact results to clients and stakeholders more effectively.

6.3. Benefit of 5D BIM

Compared with conventional methods without BIM, 5D BIM technology offers superior efficiency and accuracy in environmental assessment. Conventional methods usually involve extensive manual data collection, which is highly susceptible to data errors and information delays [64]. In contrast, 5D BIM technology can automatically obtain the resource inventory through its coding system. This reduces the need for manual intervention, which enhances data reliability [33,34].

Additionally, this study extends the 5D BIM application from economic costs to environmental costs. Although traditional 5D BIM (space + time + cost) can provide information for the space and time analysis of economic costs [17,18,19], the extension of environmental costs offers stakeholders more comprehensive information that encompasses both economic and environmental aspects.

Furthermore, this innovation of the 5D BIM coding system enables project managers to efficiently retrieve relevant environmental cost data. For instance, users can target a specific code (such as SE60) to swiftly retrieve the environmental costs associated with this code.

6.4. Limitations and Future Research

This study proposes a methodology for monetizing environmental impacts, exemplified by a prefabricated substation case study. In the future, this methodology can be extended to other building types, such as residential and commercial buildings, and compare their environmental costs. Additionally, it is necessary to compare prefabricated buildings with conventional cast-in-place buildings to help the construction industry choose more eco-friendly and cost-effective construction methods.

Regrettably, this research only considers the construction process of prefabricated buildings because it is the most distinctive compared with traditional ones [14]. Future research can extend to other stages, such as operation and demolition, to form the life cycle environmental costs of construction projects.

Regarding data sources, the environmental impact factors and willingness-to-pay data used in this study are mainly based on the existing literature, which may have certain limitations. Future research can conduct more extensive field surveys and experimental studies to obtain more accurate and detailed data, thereby improving the accuracy of environmental cost assessments.

After completing the environmental cost analysis, it is reasonable to optimize prefabricated buildings to reduce their environmental costs. However, due to a lack of environmental impact factors for environmentally friendly materials [50], this optimization work could not be carried out in this study. Future research can further explore specific measures and solutions, such as three-dimensional printing [65], to reduce the environmental costs associated with prefabricated buildings.

Regarding research methods, future research can explore more intelligent methods for evaluating and analyzing environmental costs. For example, artificial intelligence models, such as machine learning [66], deep learning [67] and extreme gradient boosting [68], can be considered to predict environmental costs at the concept planning phase of construction projects.

Unlike building carbon emissions with a more perfected policy system [69], environmental costs face fewer legal constraints. Consequently, in practical applications, environmental costs are often overlooked in the bidding process [70]. Therefore, it is urgent to introduce corresponding laws in public procurement. In future building bidding and awarding, environmental costs should be incorporated into bid-evaluation decisions to encourage projects to reduce environmental impacts.

This study has converted environmental impacts into environmental costs to understand their economic effects. Future research can compare economic costs and environmental costs and then integrate them into a single model [71,72] to help with decision making for prefabricated buildings [73]. Moreover, future research also needs to add social costs to form life cycle sustainability costs in prefabricated buildings, thus achieving a balance among the economic, environmental, and social aspects.

7. Conclusions

This study proposes a 5D BIM-enabled analysis method to monetize environmental impacts into environmental costs during prefabricated building construction. The method steps are as follows: (1) Define the spatial boundaries, temporal boundaries, and environmental indicators. (2) Obtain the resource inventory using the 5D BIM coding system. (3) Multiply the quantities in the resource inventory by environmental impact factors to obtain environmental impact results. (4) Convert the environmental impacts into environmental costs through the willingness-to-pay approach.

Taking a prefabricated substation as an example, its environmental cost is 186,638.63 CNY (172.81 CNY/m²). Among them, climate change accounts for the largest proportion (91.2%), followed by photochemical ozone (4.1%). The sensitivity analysis further reveals that the monetary value of climate change is the most sensitive variable, while other environmental indicators can be ignored. From the spatial dimension, the prefabricated walls contribute the most to environmental costs (42.5%), followed by the prefabricated beam-slabs (22.7%). From the temporal dimension, material production is the core stage, accounting for 78.6% of the life cycle, which should be the focus for attention and optimization.

This study converts different environmental impacts into unified environmental costs in monetary form, providing a straightforward indicator for stakeholders to comprehend prefabricated buildings. In addition, this study extends the application of 5D BIM to environmental costs, enabling their spatial and temporal analysis.