by Ali Karakhan and Ola Alsaffar
Photo © www.bigstockphoto.com
Construction operations are highly fragmented and complex in nature. This often leads to high levels of waste, making it difficult to build sustainable projects. This article explores an integrative approach to building green, lean, and safe projects—it proposes incorporation of lean construction strategies into sustainable design and construction to achieve desirable outcomes benefiting society, economy, and environment.
The construction industry is one of the largest sources of waste. It is estimated the built environment accounts for almost:
- 40 percent of total energy use;
- 12 percent of overall water consumption;
- 68 percent of total electricity usage; and
- 38 percent of greenhouse gas (GHG) emissions.
For more, consult the 2012 Effects of Lean Construction on Sustainability of Modular Homebuilding by I. Nahmens and L. Ikuma.
Additionally, construction waste composes “40 percent of landfill materials.” For more information, read the 2011 Fundamentals of Building Construction: Materials and Methods by E. Allen and J. Iano. The high percentage of waste in construction brings about various negative implications.
Given the high amount of waste in construction, the United Nations Environment Program (UNEP) has stated stakeholders can play a substantial role in mitigating construction waste and positively influencing society, economy, and environmental phenomena, such as global warming. Read the 2011 Greening Project Management Practices for Sustainable Construction by L. Robichaud and V. Anantatmula for more information.
Sustainable development has gained a momentum in the industry—many governmental and nongovernmental agencies have encouraged the incorporation of green practices, products, and procedures into construction operations. For instance, several local jurisdictions nowadays offer financial incentives and tax exemptions for teams incorporating green elements and sustainable practices into their building projects. (Consult the fifth edition of The Construction Chart Book: The U.S. Construction Industry and its Workers, published in 2013 by the Center to Protect Workers’ Rights [CPWR] for details.) Some cities and local governments have also enacted regulatory requirements involving green standards and environmentally responsible practices. These efforts aim to eliminate product waste and improve the final product’s sustainability.
LEED rating system
The construction industry employs several performance metrics and rating systems to assess and evaluate sustainability, but the Leadership in Energy and Environmental Design (LEED) system—a certification program initially developed by the U.S. Green Building Council (USGBC) in the 1990s—is the most recognized metric for sustainable design and construction. The program includes requirements project teams need to address before and during construction to eliminate product waste and enhance the three pillars of sustainability—social, economic, and ecological.
Such requirements can include incorporation of specific green design elements and sustainable practices to enhance people’s lives, improve project performance, and achieve environmentally sustainable outcomes. As project teams satisfy more requirements, they earn more points under the LEED program. The points determine the level of LEED certification a project eventually obtains. There are four levels of certification:
- certified (40-49 points earned);
- Silver (50-59 points earned);
- Gold (60-79 points earned); and
- Platinum (80+ points earned).
Lean construction practices
The efficiency of the process is an equally important element to eliminate waste from construction projects. One can implement lean construction practices and techniques to do so. A concept originally adapted from the Japanese automobile industry, lean construction can be defined as a production management-based approach to project delivery, aimed at maximizing customer value while minimizing process waste. From a lean standpoint, there are seven types of waste:
- defects;
- waiting;
- unnecessary transportation of goods;
- unnecessary movement of workers;
- inventory;
- over-production; and
- unnecessary processing steps.
For more information, consult the 1988 Toyota production system by T. Ohno.
The lean system’s primary focus is stabilizing production workflow and reducing non-value-adding activities during and before work operations—all of which is expected to eliminate waste from the production process.
An integrative approach
The incorporation of lean construction practices and techniques into sustainable
Image © Ali Karakhan
development, particularly the LEED rating system, can achieve superior outcomes across the facility life cycle, eliminating not only product waste, but also process waste. Lean construction and sustainable development are complementary to each other. Sustainability primarily targets the characteristics of the final product, such as maintaining healthy indoor air quality (IAQ) and increasing the amount of natural daylight entering the building’s interior. For more information, read the 2017 Safety Innovation and Integration in High-performance Designs: Benefits, Motivations, and Obstacles by A. Karakhan and J. Gambatese.
On the other hand, lean construction strategies emphasize the transformation of inputs into outputs (production workflow) in an efficient and waste-free manner. For details, consult the 1999 paper, “Management of Production in Construction: A Theoretical View,” presented by L. Koskela for the seventh annual conference of the International Group for Lean Construction.
Construction is the process of creating and building a facility. Therefore, it is rational sustainable outcomes across the facility life cycle comprise efficient processes and high-quality products, ideally free of waste.
One type of waste that can be reduced by the incorporation of lean construction strategies into sustainable development (e.g. LEED rating system) is workplace incidents, which are considered a major source of waste in construction. (Get more information in the 2017 Influence of Lean Concepts on Safety in the Lebanese Construction Industry by M. Awada et al.) The seven forms of waste can negatively influence workplace conditions and thereby safety performance, either directly or indirectly. Lean construction strategies can be implemented during and before construction to mitigate risks and eliminate waste (e.g. quality defects and rework).
In their 2017 book, Re-examining the Association between Quality and Safety Performance in Construction: From Heterogeneous to Homogeneous Datasets, P. Teo and P. Love found a positive statistical correlation between quality defects/rework and safety accidents. Similarly, I. Nahmens and L. Ikuma reported in their 2009 Lean Construction Journal article, “An Empirical Examination of the Relationship between Lean Construction and Safety in the Industrialized Housing Industry,” that by reducing the number of times a heavy object is lifted and handled on a particular project, the time needed to complete the task is considerably reduced, leading to substantial decreases in terms of exposure to the risk of back injuries. This form of waste elimination can be achieved by using lean strategies (e.g. inventory-control systems, just-in-time, off-site construction, and prefabrication).
Waste elimination can also contribute to more social and economic sustainability outcomes. Additionally, implementing lean practices and techniques aimed at improving workplace conditions and workflow reliability can enhance safety and non-safety outcomes. Implementing, say, the last planner system (LPS)—which utilizes practices such as pull schedule, look-ahead schedule, and housekeeping aimed at improving workplace conditions—has consistently been reported to improve construction site safety. For example, effective workplace housekeeping can reduce tripping and falling hazards, eliminate unnecessary handling of materials, maximize the use of onsite space, and lower worker exposure to harmful chemical substances―all of which are expected to lead to improved workplace safety performance.
In their 2011 paper, “A Research Synthesis on the Interface between Lean Construction and Safety Management,” E. Antillón et al developed a matrix demonstrating the positive interaction between essential components of safety management (e.g. staffing for safety) and lean construction strategies (e.g. LPS). (The paper was presented in the 19th annual conference of the International Group for Lean Construction in Lima, Peru.) The developed matrix proves synergies between lean construction and safety management exist. Other research studies have constantly confirmed these synergies and linked lean implementation with improved safety outcomes. The 2005 study, “Systems Model of Construction Accident Causation,” by P. Mitropoulos et al found construction projects implementing the LPS for production planning and control had incurred significantly lower incident rates compared to projects that did not implement the LPS.
Improved life cycle safety—both worker and end-user safety—is an essential component of the social context of sustainability. For a project to be associated with sustainable outcomes across its lifetime, workflow process and production outputs should be improved. Such improvements often reflect positively on performance outcomes such as life-cycle safety. R. Ahuja in his 2013 paper, “Sustainable Construction: Is Lean Green?” (presented at International Conference on Sustainable Design, Engineering, and Construction) attributed the challenges (e.g. high waste and inefficient processes) the industry is faced with, in part, to the single and fragmented approach typically implemented on construction projects. He recommended employing an integrative approach to overcome existing challenges and achieve sustainable outcomes. This article proposes a framework to implement the intended integrative approach on construction projects using green, lean, and safe strategies.
Conclusion
An integrative approach can be established by incorporating lean strategies into sustainable design and construction to achieve superior outcomes. While sustainable development primarily focuses on improving the quality of the final products (e.g. a safe facility), lean thinking improves the workflow of the production process (e.g. safe work operations). This approach addresses both work processes and final products, leading to the achievement of sustainable outcomes across the facility’s life cycle, which benefit construction stakeholders, society, economy, and the environment.
Ali Karakhan is a PhD student in the School of Civil and Construction Engineering at Oregon State University. He holds an MS in civil engineering from the University of Baghdad, Iraq, where he worked before starting his doctoral studies. Karakhan is a student member of the American Society of Civil Engineers (ASCE) and the American Society of Safety Engineers (ASSE). He can be reached at karakhaa@oregonstate.edu.
Ola Alsaffar is a registered civil engineer in the Iraqi Society of Engineers. She holds a BS in building and construction engineering from the University of Technology, Baghdad, and previously worked as a lab assistant in the civil engineering department of the University of Baghdad from 2012 to 2013. Alsaffar can be reached at aulla.aa.2013@gmail.com.
