2.1. Reducing GHG Emissions
MC creates avenues for reducing GHG emissions from the CI, which is highly beneficial for CC mitigation as these emissions are widely regarded as major contributors to CC. Multiple studies have reported lower emissions for MC than traditional construction methods. MC can induce a 46.9% reduction in GHG emissions when measured against the GHG emissions of on-site construction
[23].
Figure 1 compares the lifecycle GHG emissions of modular and on-site construction. Pervez
[23] and Quale
[24] reported a 51% and 30% reduction in MC emissions, respectively, deeming it more sustainable than on-site construction. Kamali
[25], however, in their study, argued that MC can render a 12% reduction in GHG emissions compared to on-site methods, emphasizing the lower carbon footprint of MC. Other relevant findings suggest that the most significant GHG sources in construction projects include embodied emissions, emissions during the transportation of materials (modules), emissions pertinent to construction processes, and emissions during deconstruction
[26].
Figure 1. Comparison of lifetime GHG emissions of modular and onsite construction based on published studies
[23][24][25].
According to Pervez and other literary studies, the embodied GHG emissions of building materials are responsible for the highest number of emissions in both modular and on-site construction
[23][27]. However, MC achieves a substantial 51.8% reduction in embodied emissions compared to traditional construction, owing to the materials employed in it
[28]. On-site construction relies heavily on using concrete as a primary building material. Around 60% of conventionally built structures are comprised of concrete, notorious for its detrimental effects on the environment, especially its exaggerated GHG emissions, which incite CC
[29][30]. Research has indicated that the concrete industry accounts for 8% of total GHG emissions worldwide
[31]. Therefore, excessively using concrete in on-site construction is responsible for the high embodied GHG emissions
[31].
On the other hand, MC utilizes comparatively eco-friendly materials like timber, steel, plywood, and gypsum boards in its building components
[27]. Even when MC utilizes concrete for building components, the proportion of concrete used in preparing modules is much lower than in traditional methods
[32]. The departure of MC from Portland cement concrete as its primary building material is the major reason for lower embodied GHG emissions
[33].
Table 2 compares the carbon emissions of primary building materials used in MC (steel, timber) and on-site construction (concrete). It is evident from the table that the literature attributes lower embodied GHG emissions to steel and timber as compared to concrete, accounting for the reduced embodied emissions in MC. Tavares et al.
[27] reported 27% and 48% lower embodied GHG emissions for steel and timber, respectively, when measured against concrete. Hart et al.
[34] documented similar findings, with steel and timber showing 18% and 47% lower GHG emissions than reinforced concrete. The lowest difference in GHG emissions between steel and concrete was reported by De Wolf
[35], who argued that steel has 7% lower emissions than concrete. However, De Wolf
[35] documented 48% lower GHG emissions for timber.
While it is noteworthy that MC involves higher embodied carbon emissions in metal, steel, and gypsum boards compared to on-site construction, the definitive difference lies in the impact of ready-mixed concrete (RMC) on emissions. RMC emissions in traditional construction are nearly four times higher than MC. This disparity predominantly leads to on-site construction’s embodied carbon emissions being 1.6 times greater than MCs
[25]. Moreover, MC is highly receptive to the use of novel and sustainable building materials such as cross-laminated timber (CLT) panels, recycled plastics, and fiber-reinforced polymers (FPR), unlike traditional construction, which creates opportunities for further reducing embodied GHG emissions in MC
[36].
Table 2. Comparative analysis of embodied carbon emissions of primary building materials used in MC and onsite construction.
Emissions from transportation are usually reported to be on the higher end in MC. The reason is that transportation distances are increased in MC projects as raw materials are first delivered to the modular factory, where building modules are prepared, followed by hauling the fabricated modules to the construction site for assembly
[39]. Conversely, on-site construction only involves transporting materials from distributors to the construction site, which are used for building different components
[40]. As a result, more fuel is consumed during transportation in MC, accounting for its higher emissions. However, it is to be noted that these emissions are much lower than the embodied emissions of on-site construction materials, and the lifetime GHG emissions of MC are still lower than those of traditional construction despite having higher transportation emissions
[23]. Another notable point in this regard is that many studies only assess the emissions during the transportation of materials or modules to the factory and construction sites while ignoring the reduced number of trips observed in the case of MC owing to its bulk delivery of prepared modules
[27]. MC also minimizes the redundant tours of contractors and subcontractors to the construction site owing to better planning and scheduling; hence, sites are visited only when necessary, unlike in conventional construction
[41]. Emissions due to the overheads of construction sites are also a significant contributor to GHG emissions that are cut down or largely mitigated in MC
[42]. These aspects further advocate MC’s utility in lowering the CI’s GHG emissions.
The emissions incurred during the building phase owing to equipment use and construction operations are also lower in MC
[43]. This is mainly due to optimized resource and equipment allocation in MC, which reduces unnecessary fuel use, resulting in lower emissions
[44]. For instance, MC typically requires a smaller on-site workforce than traditional construction. This means fewer commuting workers, fewer idling vehicles, and less equipment at the construction site, reducing emissions
[45]. Moreover, MC relies on off-site fabrication, resulting in less on-site equipment and machinery. For example, in MC, materials are often precisely cut off-site, reducing waste and the need for on-site machinery like saws and grinders. This minimizes the use of energy and emissions associated with operating these tools and reduces the transportation of waste materials to landfills, further reducing GHG emissions incurred during the process
[44].
Similarly, the end-of-life (EoL) emissions in MC are also lower than in traditional construction, as prefabrication allows design for deconstruction (DfD), which is acclaimed for lower emissions than the deconstruction techniques observed for on-site construction
[45]. DfD facilitates the decommissioning of buildings using less carbon-intensive equipment. In contrast, traditionally built structures are demolished using heavy machinery that consumes fuel generously and emits high amounts of GHGs
[46]. Moreover, the resources salvaged at the EoL in MC are highly reusable, reducing the demand for raw material production, which is responsible for excessive GHG emissions
[43]. These aspects of MC advocate its adoption for CC mitigation as it fosters chances for reducing GHG emissions in the CI.
High GHG emissions attributed to the CI are a key contributor to CC
[26]. Curbing the GHG emissions from the built environment remains pivotal in effective CC mitigation
[47]. MC paves avenues for CC mitigation by reducing GHG emissions compared to traditional and on-site methods of construction
[46]. The controlled environment, factory setting, sustainable materials, and optimized equipment use are the key factors governing the lower GHG emissions of MC, which is instrumental to CC mitigation
[48]. Recycling materials and resources in MC is another aspect of reducing embodied emissions in construction as it reduces raw material input
[37]. Thus, in light of the existing literature, it can be concluded that MC offers a valuable opportunity for mitigating CC caused by the CI owing to its lower GHG emissions.
In addition to the significant reduction in embodied carbon, the thermal performance of integrated insulation materials in MC is superior to traditionally built structures
[49][50][51][52]. Li et al.
[49] highlighted that in addition to improving the design efficiency and quality of construction, MC also responds to a serious shortcoming of traditional systems, i.e., occupants’ comfort, energy savings needs, and design flexibility throughout the building lifecycle. The authors used high insulation panels and aerogel blankets as insulating materials to study integrated building envelopes of modular buildings. The aim was to check the feasibility of climate-responsive “reverse-install” techniques. The results highlighted that MC-based buildings show superior and sustainable thermal performance. Park et al.
[50] investigated MC structures regarding energy independence for pertinent usage in disaster scenarios. The authors suggested using different combinations of modular units to achieve superior thermal and energy performance. Yu et al.
[51] reviewed the pertinent literature on MC and concluded that such buildings have superior thermal performance when prefabricated facade elements are used for building retrofitting. Similarly, Liu et al.
[53] investigated the impact of future climatic changes on modular buildings in Hong Kong. The authors argued that insulations such as thick (0.06–0.1 m) polyurethane foam used in MC provide superior thermal performance and energy efficiency. Further, glazing materials, horizontal shading projection factors, and window-to-wall ratio are immune to future climatic uncertainties.
2.2. Curtailing Resource Intensiveness by Enabling a Circular Economy
Enabling a CE in the CI can pave the way for resolving its resource intensiveness through optimized resource production and consumption of resources. A CE aims to cultivate a cradle-to-cradle system in the CI whereby resources are conserved, recycled, and reused to minimize the extraction of raw materials and waste generation. This offers a potential departure from the widely used “Take, Make, Use, Dispose” approach, which is accountable for the inefficient utilization of resources in the CI
[54]. MC is regarded as an alluring prospect for implementing a CE in the CI. The synergy between MC and CE principles, as illustrated in
Figure 2, has been substantially documented and acclaimed in the existing literature
[55].
Figure 2. Links between MC and circular economy.
Switching from conventional reinforced concrete to prefabricated modules is projected to bring in a 78% reduction in material consumption. Depending upon the level of prefabrication, MC instigates 20–65% waste minimization through the backflow of resources
[56]. Approximately 80% of prefabricated modules can be recycled or reused, underscoring the importance of MC in facilitating CE practices in the CI
[56].
MC facilitates the integration of CE principles in construction by actively supporting three core strategies of a CE: (1) narrowing, (2) slowing, and (3) closing the loops. Narrowing the loop is a CE strategy emphasizing fewer resources per product to alleviate the excessive consumption of resources
[56]. Reducing the use of natural reserves in the production and consumption of resources is a fundamental tenet of narrowing
[7]. MC enables the narrowing of resources by implementing precision manufacturing in construction works. The meticulous fabrication of building components enabled by the factory setting of MC minimizes the generation of construction waste, which in turn lowers the demand for raw materials
[57]. Computer numerical control (CNC) machines, 3D printing, and laser cutting are some technologies that are widely used in MC to cut, shape, and mill the construction materials precisely while strictly adhering to the design guidelines, which prevents the excessive use of resources during the fabrication of building components
[58]. The standardization of modules produced in off-site construction facilitates the implementation of automated manufacturing systems in construction, effectively reducing variances in the final products and the redundant consumption of resources driven by such variances
[57]. The controlled environment available in MC enhances quality control in construction processes, eradicating errors and omissions sustained during the production of modular units. The improved quality control in MC mitigates the need for rework and corrections to rectify errors, thereby fostering an optimized use of resources
[58]. MC also contributes to the narrowing of resources by utilizing recycled materials in construction works, lowering the number of new resources used per product. Modular units usually constitute steel or timber as their primary building block instead of reinforced concrete, as in traditional methods. Steel and timber are recycled conveniently on a larger scale than concrete, with a heterogeneous composition calling for a complex recovery process that inhibits recycling
[59]. As a result, MC allows the procurement of recycled steel and timber in large volumes to substitute raw materials in construction to narrow the flow of natural resources in CI
[59].
Slowing down the resource loop is the CE strategy, which focuses on prolonging the functional lifespan of a product to decelerate the overall consumption of resources
[60]. MC contributes to slowing resource consumption by promoting effective refurbishment and maintenance of modules, which helps extend their lifespan
[61]. In refurbishment, buildings’ outdated and aged components are replaced or renewed through renovation, restoring their serviceability
[16]. Refurbishing traditionally built structures is difficult as their components cannot be decommissioned without destructive disassembly
[61]. However, different components of modular units are easily detachable owing to their adaptable design, which enables the disassembly of units
[45].
Moreover, refurbishing timber and steel-based structures is easier than RC structures, which gives MC an advantage
[62]. Resultantly, MC sustains the refurbishment and maintenance of modular units, more so than conventional construction, which extends their service life, slowing down the flow of resources. Another facet of MC that significantly contributes to the deceleration of resource loops is the adaptability inherent in prefabricated buildings. This adaptability allows them to serve various purposes throughout their lifespan
[62]. For instance, upon decommissioning of modular structures, their components can be used elsewhere in new or existing modular units through reassembly, which reduces the disposal of construction materials. Similarly, when modular units become outdated and unfit to serve as residential apartments, they can be repurposed with minimal modifications to serve as temporary offices or retail spaces for accommodating businesses without having to construct new buildings
[63]. Upon the dismantling of prefabricated units, the recovered materials, such as steel and timber, can be repurposed in diverse industries, including automobiles and furniture. Unlike concrete, which primarily serves the construction industry, steel and timber have diverse applications across various industries
[63].
Closing the loops aims to create a regenerative system whereby the use of each resource is maximized by techniques like recycling, reusing, and remanufacturing, extending resources’ serviceability
[60]. Developing closed-loop systems in the CI has proven to be an uphill task due to multiple barriers like deconstruction difficulty, deficient material traceability, poor reverse logistics of demolished materials, and inefficient management of CDW
[64]. However, MC resolves these impediments by fostering the DfD technique that allows for the easy recovery of products, parts, and materials when a building is disassembled or renovated
[65]. Construction elements and volumetric units in off-site construction are fabricated following DfD principles, which enables a convenient and efficient disassembly of modular buildings in the later stages of their lifecycle
[65]. The efficient deconstruction of modular structures allows up to 70% of the building components to be recycled and reused through take-back mechanisms integral to CE-based business models
[66]. The construction of buildings in the form of multiple modules increases material traceability, facilitating their recovery at EoL for renewal and reuse
[27]. As a result, modular structures streamline the remanufacturing process, enabling the restoration of products at the end of their lifecycle. This results in a simplified and efficient procedure for reprocessing and renewing products, contributing to the circularity of the MC approach.
Similarly, functional modular products with enduring properties retrieved through nondestructive disassembly procedures are recycled immediately, allowing their repeated use across multiple projects
[54]. The CDW generated during the fabrication of construction elements can be efficiently sorted and stored in off-site construction due to the controlled environment of modular factories. Therefore, in contrast to conventional construction practices whereby CDW is often relegated to landfills due to insufficient storage and reverse logistics, MC provides a systematic CDW management approach that facilitates the efficient handling of waste materials, thereby supporting recycling initiatives
[57]. Therefore, adopting CE strategies facilitated by MC can alleviate the overconsumption of resources in the CI and contribute to the mitigation of CC.
The CI’s unwarranted natural resource consumption actively stimulates CC
[67]. Adopting a CE in the CI is essential for alleviating the production of new resources, as the extraction of raw materials and the operations involved in the process are major instigators of CC
[67]. MC can uphold CE principles such as narrowing, slowing, and closing the resource loops, making it an instrumental technology in fostering resource efficiency in the CI to reduce CC
[66]. From the high recyclability of its building materials to compatibility with DfD, MC enables an efficient consumption of resources across different stages of the project lifecycle, paving the way for CC mitigation
[44].
2.3. Fomenting Energy Efficiency in Construction
MC can curb excessive energy consumption within the CI to help mitigate CC. As discussed in the previous section, MC upholds a CE, which encourages the recycling and reuse of resources, significantly cutting down the need to produce new construction materials. The production of raw materials is attributed to intensive energy consumption within the CI
[68]. According to Yewei and Jing
[69], the energy consumption during the production phase of civil building materials constitutes over 80% of the total energy utilized in the construction phase and approximately 10–15% of the entire life cycle of the building. Therefore, by reducing the production of raw materials through CE practices, MC can conserve energy in the CI. Construction equipment operations are optimized in MC owing to the improved project planning. The streamlined use of equipment in MC results in lower fuel consumption and energy leakage in construction activities
[70]. The optimization of construction activities is another appreciable aspect of MC, which mitigates redundant tasks in construction projects, thus saving the energy expended on unnecessary processes.
MC allows for a significant reduction, up to 60%, in the execution time of construction projects compared to conventional methods
[56]. The swift completion of projects cuts down energy usage associated with overheads and the use of equipment for extended periods, thus encouraging energy efficiency in processes
[56]. For example, the assembly time for prefabricated units at the construction site is lower than traditional construction, which trims the energy consumption of equipment such as cranes, rigging equipment, welding instruments, etc.
[71]. On-site construction suffers from high variances in desired output during the execution of works, resulting in reworks. However, MC benefits from a controlled environment rendered by its factory setting, which fosters standardized production of building components, largely mitigating variances from the desired output
[71]. Consequently, MC requires fewer reworks to omit errors and variances, eradicating energy loss acquired by such surplus activities.
MC can also promote energy efficiency during the operational stage of buildings by improving modular units’ insulation
[60]. MC can sustain thermally efficient infill materials that significantly reduce the heating and cooling loads of prefabricated structures, accounting for lower energy consumption during the operational stage of buildings
[72]. MC also allows for the use of optimized windows and doors for superior insulation on a large scale, owing to the standardization of modular units involved, which cannot be replicated in conventional construction due to the high variability in the design of traditionally built structures
[73]. Integrating efficient insulation materials such as glass foam, plastic fiber, and expandable polystyrene into MC is easier than in traditionally built structures, improving thermal performance
[61]. The quality control in MC garners tighter seals between building components, which prevents energy leakages, further adding to the energy efficiency of modular buildings
[58].
Furthermore, MC sustains passive or alternate energy sources that create opportunities for alleviating the stress imposed on primary energy resources by the CI
[62]. Prefabricated buildings are more akin to green roofs, which can decrease buildings’ heating, cooling, and ventilation (HVAC) requirements
[74]. Solar energy can also be harvested efficiently in modular structures, reducing modular buildings’ dependence on conventional energy sources
[75]. Cross ventilation designed into the modular units removes the demand for excessive artificial cooling and positively impacts energy consumption
[75]. Lastly, the adaptive nature of MC allows for the optimized use of natural light, departing from overdependence on artificial lighting, which contributes to decreasing overall energy consumption
[76].
The CI consumes high energy, which is responsible for instigating CC
[76]. MC paves the way towards CC mitigation by lowering such energy consumption, which is enabled by the reduced production of raw materials, an acclaimed energy-intensive process
[72]. Design optimization, reduced rework due to variances and errors, and integration of passive energy sources and sustainable materials are key contributors to energy-efficient buildings, which are upheld in MC
[74]. Owing to the mentioned competencies, MC can effectively mitigate the excessive consumption of energy in the CI and contribute to developing CC resilience.
2.4. Fostering Resourceful Land Use and Management
Most of the work is performed on-site in the case of conventional buildings. Local ecosystems, vegetation, and natural habitats are adversely affected because of the intensive land-clearing and site preparation measures required to set up the site for traditional construction
[77]. Owing to the expanded spatial requirements of traditional construction, it possesses a substantial horizontal footprint disrupting the adjacent land and environment
[76]. On the other hand, MC requires less site clearing and preparation activities as building components are fabricated in a factory. Only prefabricated units are assembled at the site, which necessitates less space than traditional construction, rendering a reduced horizontal footprint for MC
[77].
Moreover, with most of the work being performed in an off-site factory, the number of activities performed at the construction site is also significantly reduced in MC. Reducing the on-site activities minimizes the effects of construction works on the adjacent land and environment, leading to their preservation
[78]. Landfills consume ample space and valuable land, which poses challenges to effectively utilizing available land, especially in the backdrop of an increasing global population. The CI is a major contributor to landfilling as up to 35% of global landfills constitute waste from the CI
[8]. MC is attributed to minimal waste generation and efficient management of CDW owing to the fabrication of construction elements in a controlled factory setting. Therefore, the reduced waste generation observed for MC can also contribute to the depreciation of landfilling, thereby preserving the land for productive utilization
[62].
Another factor instigating the inordinate land use by the CI is the unhindered expansion of urban landscapes, which is responsible for habitat loss, fragmentation of ecosystems, and the disruption of biodiversity
[79]. Traditional construction adds to this problem because of multiple inherent constraints like a greater spatial footprint and limited vertical growth. While traditional RC structures support high-rise construction when designed to meet this purpose from the inception of a project, they do not offer sufficient options for vertical expansion of existing structures later in their lifecycle
[48]. As a result, traditional buildings fail to create useable space later in life due to a lack of vertical expansion, leading to horizontal urban sprawl
[80]. Conversely, MC facilitates the vertical expansion of existing structures, paving avenues for high-rise construction due to its adaptive building components
[80]. The ability of MC to enable vertical expansion of modular buildings in the later stages of their lifecycle can foster compact and densely populated cities to mitigate the horizontal sprawl of urban areas
[81].
Another issue that contributes to excessive land use by cities is the overcrowding of urban areas, causing cities’ outward expansion
[81]. The deterioration of urban business hubs is strongly linked to factors such as the decentralization of economic activity and the lack of facilities
[76]. The rehabilitation and repurposing of brownfields are considered pivotal in curbing the unchecked sprawl of suburbs
[82]. MC can contribute to the rejuvenation of brownfields by facilitating infill development. Infill development involves the revitalization of vacant, abandoned, or underutilized land within established communities where infrastructure is already present, serving as a solution for filling gaps and contributing to community revitalization, land conservation, and alternatives to sprawling development
[83].
MC enables development within established urban settings by using its reduced horizontal space requirements, which allows construction activities to be carried out in constrained spaces
[81]. Moreover, MC’s compact design allows for the development of brownfield sites with limited or irregular dimensions. It efficiently utilizes constrained spaces within established urban areas, adding benefits for rejuvenating crumbling city sites
[84]. Another aspect of MC that adds to the revitalization of neglected urban areas is its compatibility with adaptive reuse. Adaptive reuse extends the useful life of historic, old, obsolete, and derelict buildings. Adaptive reuse projects seek to maximize the reuse and retention of existing structures and fabrics and improve buildings’ economic, environmental, and social performance
[85].
Modular structures are highly flexible, allowing for the reconfiguration of structures to meet different purposes. Modules can be amended with minimum renovation to change their functionality depending upon the socio-economic requirements to revitalize the deteriorating neighborhoods in urban areas, enabling effective land use
[86]. The adaptive reusability of MC allows it to be utilized for mixed-use projects. Mixed-use projects are essential for optimizing urban space by integrating diverse functions within a single development, promoting efficient land use, and creating vibrant and sustainable cities and communities
[87]. Meanwhile, the inflexibility of conventional construction limits the possibilities for adaptive reuse, compelling a linear approach that is not favorable for sustainable land utilization
[86]. Therefore, by curbing the unrestrained expansion of cities through smart construction practices and revitalizing existing infrastructure, MC can mitigate inordinate land consumption, which adds to CC.
Unregulated consumption of natural land by the built environment is offsetting the climate. The CI will grow exponentially in the future to accommodate the world’s growing population
[79]. The subsequent expansion of the built environment will lead to further deterioration of the natural environment, thereby adding to CC
[80]. Strategies like infill development and adaptive reuse of existing structures are necessary to promote resourceful land used to repopulate the deteriorating parts of urban areas
[83]. Mixed-use projects enabling the same facility to serve multiple purposes are pivotal to avoiding new land preservation construction
[87]. MC can enable effective land use and management due to its versatility and reusability. MC’s advantages in fostering resourceful land use are summarized visually in
Figure 3, which advocates for its importance in CC mitigation.
Figure 3. The potential of MC in fostering resourceful land use.
2.5. Conceptual Framework for Mitigating Climate Change through Modular Construction
Drawing from the literature review, a conceptual framework is proposed to address the CC induced by CI activities through adopting MC, as illustrated in
Figure 4. The proposed framework underscores different MC-based strategies that can reduce GHG emissions, implement resource efficiency by enabling a CE, promote efficient energy consumption, and foster resourceful land use since addressing these parameters is pivotal in mitigating CC
[88]. Reducing GHG emissions in the CI requires adopting sustainable construction materials, which the mainstream adoption of MC can enable. The embodied emissions of materials like cement and concrete are exponentially high, rendering traditional construction unsustainable
[55]. MC uses concrete in much lower quantities as it predominantly relies on steel and timber for construction, making it much more sustainable in comparison
[55].
Figure 4. Conceptual framework for mitigating climate change through modular construction.
Moreover, MC is highly compatible with novel materials like recycled plastics, geopolymers, and bamboo, which can further lower the embodied GHG emissions prevalent in the CI
[36]. Recycling and reusing building materials is another aspect of MC that can reduce the demand to produce raw materials, substantially lowering embodied emissions. The flexibility of MC facilitates the adaptive reuse of existing modules, which can cut down the need to construct new buildings from the ground up. Curtailing the requirement for new construction can reduce GHG emissions incurred during various phases of construction endeavors
[67].
The factory setting and standardized fabrication procedures in MC enable the streamlining of construction activities, which removes redundant exercises and cuts down emissions
[46][89]. The fabrication of stackable volumetric units off-site can enable bulk delivery of the prepared modules to the construction site. As a result, the overall number of trips to the construction site can be reduced, lowering the associated emissions
[27]. Through a culmination of these strategies enabled by MC, GHG emissions during constriction works can be significantly reduced to alleviate the massive GHG footprint of the CI.
The resource intensiveness of the CI is another instigator of CC, which can be dealt with by employing MC, as shown in
Figure 4. MC fosters DfD due to the unique fabrication of its building components, which allow modular units to be detached, allowing for convenient disassembly of modules
[90]. As a result, modules are recovered at the EoL, which can be reconfigured for use elsewhere, thereby conserving resources by mitigating the necessity of new construction
[65]. DfD enabled by MC creates an opportunity for implementing a take-back or product as a service (PaaS) business model in the CI, which are also enablers of a CE. The building components in modular units are highly standardized in size and specifications. As a result, defective components can be refurbished or replaced conveniently with an element from a recycled module, which contributes to creating a closed-loop system that enables resource efficiency
[91].
Precision manufacturing is another MC strategy that reduces CDW generation
[92]. The fabrication of components in a controlled setting of a modular factory enables the precise cutting and shaping of materials, leading to minimal resource waste
[18]. The controlled environment also enables the effective collection, sorting, and recycling of waste, which can be reconfigured for different purposes. The minimized waste generation, along with its improved recycling, further instates the resource efficiency of MC, emphasizing its allegiance with a CE.
MC can foster superior reverse logistics compared to traditional construction by utilizing technological advancements like artificial intelligence, digital twins, and the Internet of Things (IoT)
[93][94][95]. MC favors material traceability due to labeling its components during production, digital documentation through IoT, or material passports, which aids the reverse logistics of building components at EoL
[93]. Blockchain technology is another emerging concept that can be leveraged in MC
[96][97]. Traditionally built structures do not favor reverse logistics owing to the highly heterogeneous composition of building materials like concrete, which impedes the traceability of materials for recovery.
MC offers multiple prospects to curb the excessive energy consumption in the CI. The recyclability of materials in MC alleviates the demand for raw material production, which is renowned for being an energy-intensive process
[67]. Conserving energy by lowering the extraction and refinement of raw materials is an alluring prospect of MC. During the construction phase of projects, MC can curtail the unwarranted use of energy by eradicating redundant activities and variances due to its standardization of processes
[98]. By abolishing unnecessary exercises, construction work is streamlined, eliminating energy leakage in redundant activities. Smart distribution of work packages in MC also enables the optimized use of construction machinery, curtailing equipment’s idle running time and lowering their energy consumption
[98].
MC can foster energy efficiency during the operation phase of facilities as well. In this regard, a prominent feature of MC is its ability to seamlessly integrate passive energy systems that generate renewable energy, removing excessive dependency on primary energy sources
[75]. Photovoltaic (PV) panels can be integrated with modular units conveniently, which can be used to power multiple appliances. Similarly, the modules can be enhanced with green roofs, which regulate temperature within the buildings, cutting down the HVAC requirements
[74]. Maximizing sunlight can take away lighting load as well as heating requirements. Optimal choice of windows for specific modular units can mitigate heating and cooling loads by regulating room temperature
[22]. By impeding the unwarranted use of energy in the CI, MC can contribute significantly to CC efforts, as enabling energy efficiency is key to sustainable development.
Resourceful land use for the built environment is critical for mitigating CC, and MC can facilitate it in multiple ways. MC is associated with minimized disruptions to the surroundings of a construction site. The horizontal footprint of MC is much less than that of traditional construction, as most of the fabrication is conducted off-site
[81]. As a result, MC enables the preservation of the adjacent environment as minimal disruption is caused to surroundings. MC facilitates the vertical expansion of existing structures and new buildings, creating venues for densely populated and centralized urbanization
[81]. Such centralization of cities hinders urban sprawl, which can reduce the horizontal expansion of the built environment, thereby preserving natural land, which is crucial for resisting CC.
Another strategy that can be implemented through MC is fostering infill development in neglected urban areas to address their socio-economic needs for revitalization
[83]. This feature of MC has alluring implications for promoting effective land use, as the rejuvenation of brownfields can draw people to established areas of the cities, mitigating the need for new construction
[80]. MC facilitates mixed-use, which enables modular units to serve different purposes and meet different requirements. MC also facilitates a phased development strategy, providing the flexibility to incrementally introduce new modules or functions. This approach is well-suited for dynamic mixed-use projects, allowing them to evolve, expand, or adapt to shifting demands over time
[86]. MC further facilitates versatile and adaptable designs, incorporating diverse functions within a unified structure. For example, a modular building can seamlessly integrate commercial spaces on its lower floors while featuring residential units on the upper levels, emphasizing MC’s compatibility with mixed-use projects
[86]. Due to this feature, the same buildings or facilities can serve multiple functionalities, thereby trimming down the requirements for new construction to conserve land.
The adaptive nature Inherent to MC allows for the reconfiguration of older modular buildings through refurbishment and renovation. Refurbishing modular buildings is easier as components are easily replaceable, extending the service life of units
[69]. As a result, prefabricated units can serve for a longer time, which assists in preserving the natural environment by revitalizing established buildings.