Modular construction, or simply prefabrication, is focused on the construction use of repeated units, modes, components, and so forth, produced off-site in a factory setting. That is why, as Jeffrey Molavi and Drew L. Barral discussed, its proper application would require many considerations to design, coordination, and administration.
Costs vary between projects for multiple reasons. Regarding labor, one should consider obstacles to assignment completion, productivity levels, and vulnerability to uncontrollable factors (i.e., weather implications). But with modular construction, these critical factors are substantially reduced. On the other hand, when viewing the extensive planning required for project’s delivery of prefabricated parts, there is much room for error, such as the incompetence of the prefabrication suppliers to provide quality, flawless parts. Similarly, there is an inverse relationship between externally, the financial liability of overseeing the construction process, and internally, the administrative management of stakeholders with varying backgrounds and goals, including the profit-maximization of their role.
There are significant potential benefits of modular construction, such as its ability to directly engage and coordinate among various industrial trades (i.e., electrical, mechanical, plumbing). For example, it is less obstructive to install piping and ductwork after finishing its interior work, than before or during that process. Hence, subcontractors are more accepting of the aftereffects of the prefabrication planning segment of the project’s construction. Then, the general strategy would be to overlap the design and procurement activities, which would also leave room for innovation to achieve higher profits internally. Disadvantages arise from the addition of prefabrication procurement activities, ranging from additional costs of material, transportation, and installation, to adjustments in construction management responsibilities and quality inspection difficulties. That is why it is harder to guarantee reliability from all the subroutines of the project’s construction. To counter these impacts, Molavi and Barral aimed to devise a secure method for using prefabrication efficiently, regarding cost and constructability, based on real-world building projects.
They chose a general urban vertical building (i.e., office building) as their subject of study, to use its construction process’ repetitive nature to explore the potential for prefabrication for various construction trades. For instance, the staircases, room interior, wall exterior, window placement, floor layout, and so forth, are similar enough to draw the connection and apply relatively simple revisions towards their components, thus allowing for a broad range of prefabrication use. Then, to maximize the advantages of prefabrication, if approved, general contractors could work with reliable, multi-performance (regarding trades) suppliers and subcontractors to simplify divisional management. Similarly, they could make use of the smaller number of stakeholders involved to internalize coordination to reduce risks of failure in administration and procurement. Then, the total vulnerability would be concentrated on time efficiency, communication, and prefabrication quality, thus narrowing its original scope in traditional construction. As a result, sustainability would be achieved at its maximum potential, though contingent upon its corresponding production rate and satisfaction.
This paper is useful precisely as a reference source in later-released, empirical research papers about prefabrication, hence its weaknesses: a lack of data and use of underlying assumptions. However, of interest is its position on the initial stages of development and perception of the prefabrication technology and application, especially towards sustainability. Due to its suggested implications of the inverse relationship between sustainability and constructability, it becomes apparent that a cost-benefit analysis for the present situation is critical to a better understanding.
Although prefab metal buildings are known to offer significant advantages to environmental sustainability and constructability, applying it on a full scale of infrastructural projects is very unlikely for developed countries due to their urbanization implications. In the case of China, as Jingke Hong, Geoffrey Qiping Shen, Zhengdao Li, Boyu Zhang, and Wangqiu Zhang have found, construction stakeholders often attributed this to the current lack of transparency in costing feasibility and assessment. Since there was little data available to reference these barriers to economic mitigation before their study entirely, the team researched to produce a robust cost-benefit analysis for the use of prefabrication for construction at China.
Focused on residential building construction: costs associated with prefabrication shown in the graph below. Notably, materials (concrete and steel) cost the most, due to their large quantities and high market price, followed by labor input. Compared to traditional construction, prefabrication used more sophisticated transportation logistics to prevent damaged components, which also contributed to the cost gap. Overall, to understand prefabrication costs in greater detail, one would look at the material intensity of the prefabricated components, based on contract specifications and structural purposes, as well as their involvement in the construction process.
The team also found, per regression analysis, that the prefab buildings like metal garage prices intensity positively correlated with the precast rate (the percentage of prefabrication used in a total concrete portion of the building structure). It would mean that the economic costs of adopting prefabrication exceeded the benefits of their improvements on constructability, thus leading to discouragement in using prefabrication. From an additional breakdown on cost incrimination of prefabricated components, cost increased based on the extent of related factors such as manufacturing, miscellaneous work, and logistics complexity. The latter could then break into labor costs, consultant services, and drawing/architectural work. To note, these subfactors are primarily dependent on geographical dynamics, such as the market’s maturity and local availability of prefabrication suppliers and resources.
Due to the strong relationship between cost overrun and precast rate, the research showed a great need for cost-saving strategies. Proposals included maximizing prefabrication (through mass production, continuous bulk orders) to better constructability efficiency while making use of the cost-benefit of the economics of scale. Since currently the industrialization deficiency is applied to only a small portion of the building, not all the structural and economic benefits captured. Then, it would be crucial to merge an environment-friendly, multi-performance materials approach to cost-effectiveness in the management of prefabricated components. Also, the immaturity of the industrialized prefabrication market reflected in the cost incurred during the onsite installation of prefabricated components should be addressed to minimize potential, future conflicts. Externally, it would be beneficial to increase governmental involvement in the industry to promote prefabrication technologythrough financial support and incentives for both stakeholders and suppliers.
The research design of this paper was very well-developed, with appropriate consideration given to multiple factors of interests, including local significances, specialization, industrialization and urbanization gap, and so forth. Despite the number of assumptions used to create and carry out the research process, they were all accounted for in both logical reasoning and data analysis, as well as further synthesized in the discussion portion assimilated to my review. At the same time, they used various methods in consolidating the data, including economics and construction logistics. That is why, it appears that the only weakness this paper contained was the real-world restraints and implications on their research, due to the prematurity through the relevant context of urbanization in China.
Thus far, economic and environmental sustainability had been accounted for and compared to constructability, to obtain an impartial evaluation of their significance on the construction process. Viability was also reviewed per the lens energy consumption, to optimize a concrete structure’s embodied energy. Then, approaches and barriers to achieving were considered simultaneously to determine future options. Next, modular construction, also termed prefabrication, was discussed and viewed in its sustainability potential for the construction process. In a more recent context, a cost-benefit analysis was analyzed, about China’s urbanization, to detail the implications of prefabrication, for both technology and management, in the construction industry.
Across disciplines, for sustainability, there was much attention to concrete life cycle, in its economic costing and service duration, for a building’s project timeline. Embodied energy was also a key factor of sustainability, for which careful manipulation and distribution of low energy-intensive materials through reinforcement held potential for greater efficiency. Regarding prefabrication, after close examination of sustainability and constructability, their inverse relationship left much room for the external promotion of utilization. In the clear case of urbanization, much room went for cost-effectiveness and material efficiency, despite the observed benefits of prefabrication. Lastly, most papers indicated possible governmental involvement, mostly financially, in overcoming the economic challenges of the markets for the industry. In that case, it is even more crucial to affirm the cost values and develop a multi-performance procedure for ensuring accuracy and consistency before policy implementation.
In response to “What is the trade-off between sustainability and optimization of concrete utilization within a construction context?”, Concluding the literature review there is no satisfactory answer. Per a construction view, supposing that constructability implies optimization, the observed, real-world relations hold inconsistencies among projects regarding actual usage’s optimization. It is especially relevant to prefabrication application, though more prevalent in developing countries. In that case, it would be more precise to consider the interrelations of the factors above to understand better and indicate their relative significance or impact of the construction industry. To note, it becomes sensible that due to research constraints, this process would be inefficient for time and cost. Then, the pace of the market that serves the industry could be considered relatively stagnant, which presents a problem for, especially urbanization.