Integrating lean and sustainability for waste reduction in construction from the early design phase

ABSTRACT

Lean and sustainability are found to have the same agenda of waste reduction. Sharing waste reduction is particularly important for understanding how lean and sustainability can be weaved together to support mutual benefits. However, many publications concentrate on these strategies in isolation, paying less attention to their integration in the design phase. This paper presents an exploratory study from extant literature. It reviews more than 30 papers that have been published from 2018 to 2023 and examines the concepts of lean and sustainability on the issue of waste reduction from the early design phase. It explores the opportunities to enhance environmental and construction performance by implementing sustainability-lean practices to reduce the sources of waste generated in different design stages. Results indicate that ‘Clearness, recognition, and Communication’, ‘Inappropriate supplying of information’, ‘Coordination and accuracy’ and ‘Design Expertise’ are the most important sources of design waste since they have the highest number of waste causes. Results show that design waste sources are affected the most by a wide practice of embedding waste reduction strategies in the Preparation and Briefing and Technical Design stages. The paper shows the most applicable lean tools that aim to reduce waste from the early design phase. The overall conclusion of this study is compatible with the same studies worldwide, which were applied in terms of increasing the performance of the waste reduction plan in construction by identifying the sources of design waste to achieve positive outcomes in terms of environmental, social, and economic dimensions.

KEYWORDS:

• RIBA plan of work
• design waste sources
• design waste causes
• lean design seven wastes
• lean tools
• resources and material
• 3 R s strategy
• designing out waste

Introduction

The term lean is an approach that was developed in the Japanese automotive industry and then converted and promoted to be appropriate for use in the construction industry after the publication of the Koskela report to the Center for Integrated Facility Engineering (CIFE) at Stanford University, ‘Application of the new production philosophy to construction’ in 1992 [1]. It was highlighted that lean construction can achieve positive impacts on the construction industry after studying the deficiencies of the traditional system. It aims to eliminate waste, satisfy the client, focus on value for money, enhance communications, and improve quality management, and supply chains from the early design phase [2].

Otherwise, sustainability has been crucial within our societies and economies since the publication of the report of the World Commission of Environment and Development (WCED), ‘‘Our Common Future” in 1987, which describes the idea of sustainable development in connecting social, resources, and environmental concerns through a long-term environmental perspective [3]. The most important aspects of sustainability are the environment, society, and economy. They can be described through different approaches related to environmental protection, climate change reduction, fossil fuel replacement, human well-being, security of supply, and living standards improvement [4].

The construction industry is one of the main industries expected to contribute to enhancing these approaches; therefore, the definition of sustainable construction is necessary. Sustainable construction is known as the response of the building to the challenges faced by sustainable development [5]. It aims to use the minimum amount of building materials and energy consumption that leads to reduced pollution and waste at each phase of the project. Starting from the design phase, this reduction can be achieved by creating widely accepted architectural design standards for building performance and performing a comparison with efficient sustainable building designs [6].

Lean and sustainability seem to be two independent and separate strategies. However, it has been found that they are interdependent and share the same agenda of waste elimination. Recognizing the commonalities of the goals of both strategies can lead to a better understanding of the components of each one. This can help integrate both concepts during the early design phase to protect human health, the surrounding environment, and economic development without affecting the future [7]. It is important to note that although many literature sources stated that lean concepts can be applied in the design phase of a construction project to reduce costs and achieve sustainability. The concept of integration was only implemented in construction, in the operation of a process, in manufacturing, or on-site processes, paying less attention to its implementation in the early design phase and the identification of its impact on the issue of waste reduction [8].

Thus, this paper investigating the concepts of lean and sustainability, highlighting the opportunities to enhance environmental and construction performance by implementing sustainability-lean practices that relate to waste reduction in the early design phase is the main objective of this study.

Materials and methods

Research methodology

The literature study behind this paper aimed to explore the opportunities to enhance environmental and construction performance by implementing sustainability-lean practices that relate to waste reduction from the early design phase. To do so, the relevant studies were located on the Web of Science, Science Direct, Google Scholar, and Scopus databases, the papers published between 2018 and 2023 are investigated by using titles, keywords, and abstracts in the manual search process. The used keywords on the database are lean, sustainability, waste reduction, resources and materials and early design phase among articles and review papers in both Scopus and Web of Science databases. The initial search returns 50 papers.

The literature review consists of three stages to define the most relevant papers in the field of construction waste reduction by the integration of lean and sustainability from the early design phase. These stages are database selection, sample searching, and sample selection. Similar study used the same methodology to examine the waste management strategies [9]. Literature review methodology is shown in Figure 1.

Figure 1. Literature review methodology. “Source. Authors’’.

Database selection

There are several database engines are utilized to follow the path of scientific publications such as Web of Science, Science Direct, Google Scholar, and Scopus database. Research conducted by [10] implied that the Scopus database has a preference over the other databases; however, there is another study conducted by [11] that ensured that the journal classification of Web of Science is preferred. Thus, this paper considers both the Scopus database and the Web of Science database, meanwhile, Google Scholar is also used as an assistant tool.

Sample searching

For this purpose, the papers published between 2018 and 2023 are investigated by using titles, keywords, and abstracts in the manual search process. The used keywords on the database are lean, sustainability, waste reduction, and early design phase among articles and review papers in both Scopus and Web of Science databases. The initial search returns 50 papers.

Sample selection

After reading the abstracts of 50 papers in the first step, the second step is to identify the suitability of papers based on an in-depth reading of the whole paper, so the number of 30 papers with the most relevant content for construction waste reduction from the early design phase by the integration of lean and sustainability, are selected. The results of this search indicate that there are 24 articles and 6 review papers. Among the years, the maximum number of papers were published in the year 2022 (8 papers), followed by 2019, 2020 and 2023 (5 papers) as shown in Figure 2. Figure 3. Shows the types of the 30 located studies. Meanwhile, regarding journals, the highest number of articles were published in the Sustainability Journal with 4 articles and 3 published articles in the Journal of Cleaner Production.

Figure 2. Publication period of analyzed studies. “Source. Authors’’.

Figure 3. Types of the located studies. “Source. Authors’’.

Results and discussion

Waste in construction

Waste in construction has been defined as various building materials generated directly or indirectly from previous construction activities, and they do not have remaining value such as bricks, wood, concrete, etc. Also, it has been found that construction activities are responsible for 35% of the total waste when compared with other activities by other industries [11]. Despite, the difficulty of evaluating the average of waste generated in sites exactly due to different construction conditions, It has been concluded that between 4% to 30% of transformed building materials to the site are converted to waste because of different purposes during the construction, this is based on what was emphasized in August 2022, at the International Conference on Civil and Architecture Engineering (ICCAE-14), ‘Causes Influencing Construction Waste Generation During the Design Process: An Analytical Study’.

Types of construction waste

Construction waste is a global issue that negatively impacts the project’s performance, society, and the environment. Waste can be generated in different shapes as shown in Figure 4. Waste happens in the shape of material, time, and cost overruns [11].

Figure 4. Classification of construction waste. “Source. Authors after [11,12]’’.

Material waste as a physical construction waste

Material waste is the major shape of physical waste generated from construction activities such as bricks, wood, concrete, etc [11]. Also, it has been proven that material waste has negative impacts related to increasing costs and harming the environment. One of the results generated from the huge amount of material waste is illegal dumping. Illegal dumping is a law-breaking activity of dropping waste into the land. It is a worldwide harmful activity because it causes severe problems to the environment. The illegal dropping of physical waste on the land is steadily increasing, which leads directly or indirectly to global pollution [12]. Thus, it is very important to understand the current situation by identifying the root causes of the waste in construction to avoid negative outcomes as described in the following sections.

Cost and time overrun as a non-physical construction waste

On the other hand, waste can be classified as non-value-adding activities [12]. The expression non-value adding activity is applied to distinguish between physical waste and other waste types that happen during construction [13]. Also, it is known as intangible waste. A study [14] identified nonphysical waste as any activity that consumes resources but brings no value such as errors that require corrections, overproducing, extra processing, waiting for other activities, and unnecessary movements. All these activities require more time and money which cause failure for most construction projects. In other words, nonphysical waste influences the economic growth and social development of countries significantly [13].

Root causes and impacts of construction waste

The most efficient way to reduce waste is to identify its causes, revealing that there are common factors that mostly cause most of the waste occurring in the construction industry from the early design phase. These factors force construction organizations to develop and implement new rules and priorities that help in controlling waste generation at the source to minimize the negative results related to human health and the environment [13,14]. Table 1 clarifies the root causes of waste where their impact was explored related to sustainability pillars namely environment, society, and economy.

Table 1. Root causes of construction waste.

Construction waste’s main causes	Root Causes	Impact	References
Design	-Design changes. -Design Errors. -Change in client requirements. -Complex design. -Errors in the contract. - Insufficient design quality and quality control. - Lack of necessary design information -Bad selection of material. -Communication problems.	Increasing the cost due to the rework and extra processing (economic impact).	[6] [12] [15]
		Changes lead to waste in the material which can be thrown and releases harmful gases (environmental impact).
Procurement	- Limited early coordination among parties during design. -Waste from packaging. -Mistakes in quantity. -Suppliers’ error. - Purchased goods do not agree with the requirements.	Extra materials lead to resource waste (economic & environmental impacts).	[9] [14] [12] [15]
Workers	-Workers errors. -Overtime. -Time stress. -Lack of training.	Stress at work cause health issues (social impact).	[12]
		Errors lead to inadequate usage of material. (economic & environmental impacts).
Site management	-Late information flow. -Leftover materials. -Procedures in an uneconomic way. -Using the wrong materials -Bad material handling	Increasing the cost of the material because of rework and redoing (economic impact).	[15]
Construction operation	-Poor supervision. -Poor experience and knowledge. -Inadequate planning	Lack of experience leads to rework and overdoing (economic impact).	[15]
Storage	-Inadequate storage methods.	Material consumption (environmental impact)	[6,14,15]
External Factors	-Weather - Lighting problems -Inaccessible project location -Governmental issues. -Stealing issues -long project duration	Material damage and waste of resources (economic & environmental impacts).	[13] [14]

Despite there are different factors that contribute to generating waste in the construction process. The most significant cause of waste is associated with design activities that happen during the design phase [15]. Therefore, design stages and sources of construction waste generation from the early design phase are studied in detail in the following sections.

Waste in design

One of the most important phases that any construction project goes through is the design phase [5,6], where the client’s needs are transformed into technical drawings and specifications [7]. Also, the design phase is considered crucial due to the critical decisions that influence the performance of the project. It contains the development criteria through several actions that are arranged based on their necessity. Accordingly, the priority of these actions in the project is assigned. Thus, huge benefits are predictable when waste reduction techniques are applied from the early design phase [15], as they concentrate on identifying the sources of construction waste generation and defining creative solutions that achieve the desired outcomes.

Design phase stages

The Royal Institute of British Architects (RIBA) plan of work outlined the design phase into five stages as shown in Figure 5. In this section, these stages are described as follows [16]:

• Stage 0 - Strategic Definition (SD): The first stage of the RIBA plan of work illustrates the project brief including project scope, design aspects, the required project outcomes, and sustainability goals. These are investigated in the context of the site context, lessons learned, and project circumstances to integrate them into the upcoming stage. Developing a project program that contains the responsible parties, feasibility studies, project risks, and sustainability methods is the expected result of this stage.

• Stage 1- Preparation and Briefing (PB): As can be understood from the name of this stage that it is concerned with gathering all the data from the previous stage to initiate the first brief draft including the project goals and the client’s business situation. Essentially, this stage also ensures the execution of any relevant feasibility studies, risk assessment reports, project surveys, budgets, sustainability strategies, and execution plans.

• Stage 2 - Concept Design (CD): In this stage, the focus is on the architectural design concept. The designers present to the client visualizations that explore the ideas based on the project brief. Moreover, several instructions can be employed to prepare the structural design, building services, and project specifications proposals.

Figure 5. Design phase stages “source. Authors after [16]’’.

• Stage 3 - Spatial Coordination (SC): More considerations are given to design studies and analysis. The design is achieved more clearly and developed in parallel with structural design and cost exercise to ensure its possibility in construction. In addition, the evaluation of the design concept with the spatial measures takes place in this stage.

• Stage 4 - Technical Design (TD): all the information is prepared, developed, and detailed for the construction.

A deep identification and understanding of these stages are certainly useful in identifying waste reduction techniques using lean and sustainability concepts that fit each stage of the design based on its characteristics to improve the currently existing strategies.

Impact of the design phase on construction waste generation

There is an agreement about the relationship between design and construction waste in literature sources [10,11], the literature is rich in this discipline. However, publications that specifically identify design causes and sources in relation to their origins from the early design phase are absent from the literature [1,17]. Therefore, Table 2 underlines the different causes and the sources of these causes based on what was confirmed in August 2022, at the International Conference on Civil and Architecture Engineering (ICCAE-14), ‘Causes Influencing Construction Waste Generation During the Design Process: An Analytical Study’. These Causes are the reasons behind 33% of construction waste generation as it has been found that 33% of waste generated on construction sites is connected to design directly or indirectly [17].

Table 2. Causes and sources of design waste.

Causes of Waste	Sources of Construction Waste generated in the design	References
Inappropriate supplying of information	- Poorly defined waste reduction roles. -Waste reduction strategies are not included in contract documents. -Missing waste reduction guidelines - No waste reduction target setting. -Delay in providing information to the late design stages. - lack of necessary design information -Unrespect for environmental requirements	[6] [15]
Clearness, recognition, and Communication	-Client is unaware of waste reduction advantages. -Waste reduction is not a requirement among designers. - Inadequate communication between project parties. -Design changes by designers. -Insufficient and incomprehensible project brief. -Design doesn’t include client requirements because they are not clear enough. -Delay in information flow. -Design visualization is missing. -Design complexity -Difficulty in communication among different specialists.	[5] [15]
Feasibility study	-Inadequate feasibility studies. -No waste management feasibility studies.	[7]
Coordination and accuracy	-Limited early coordination among parties. -Waste reduction strategies are not involved during design. -Errors in design. -Errors in construction drawings. -Insufficient design quality and quality control.	[17]
Project users	-Users rarely participate in the briefing process. -Unrespect for users’ cultures. - Several last-minute changes provided by the client.	[6] [7]
Value	-Frequent value engineering changes.	[18]
Quality and Sustainability	-Upgrading project facilities -Bad quality for the selected materials. -Unrespect for the complete project life cycle.	[3,4,7]
Technological Advancement	Insufficient response to technological advancement.	[15]

These sources in the design phase that generate waste in construction must be mitigated or preferably eliminated [15]. Therefore, environmental problems related to natural resources, pollution, contamination of water, landfills, gas emissions, global warming, and human health can be avoided. Waste reduction is a strategy that must take a lot of attention from the early design phase [6] by fixing human activities and improving the current applications of design management as described in the following sections [18].

Construction waste reduction from early design phase

As mentioned before, starting the waste reduction strategy from the early design phase by refining the project design through well-defined waste reduction responsibilities among participating parties minimizes waste generation in the construction, saves natural resources, and protects the surrounding environment [18]. Based on the upcoming analysis, it could be observed that the paper identified four main themes in literature studies by which the researchers attempted to examine the construction waste reduction from the early design phase as follows:

1. Categories and sources of causes that are responsible for construction waste generation from the early design phase have been mentioned in detail in the previous section [3–7,13–15].

2. The implementation of advanced technologies and methods of construction waste reduction from the early design phase [15–18].

3. Construction waste reduction according to the architect’s point of view; they believed that waste generated during construction is related to site operations and rarely generated from the design phase [19,20].

4. Challenges faced the application of construction waste reduction from the early design phase such as Architectural technologies, waste reduction investment, economic incentives, etc. All these challenges must be identified as they are crucial to implementing waste reduction strategies from the early design phase [8,21].

Essentially, this study is focused on the first theme which identifies the categories and sources of causes that are responsible for construction waste generation from the early design phase.

Waste reduction from lean perspective

Lean in the AEC industry is a new approach that focuses on waste reduction, continuous improvement, process control, flexibility, optimization, people utilization, and customer satisfaction [1,2]. The core concept of lean is depending on dividing all activities of the system into two main groups, based on adding value to the process. Thereby, the value-adding activities are defined as ‘conversion activities’ or ‘former activities’, while non-value-adding activities that consume resources and time are known as ‘flow activities’ or ‘latter activities’ [4]. The application of lean thinking in construction leads to improving conversion activities and eliminating flow activities [6]. Thus, applying these principles will not only lead to significant benefits to the design and construction companies by becoming a cost leader when eliminating cost-consuming flow activities in the system and diminishing the amount of waste generation [7] but also, to the communities and environment itself [14].

Waste in lean context

A study [49] defined waste as activities that result in utilizing materials, energy, sources, labor, or equipment in unneeded amounts to deliver the building. Waste has been divided into seven main categories recognized by the literature related to lean philosophy namely transportation, waiting, overproduction, defects, inventory, motion, and extra processing which are listed and described in Table 3.

Table 3. Waste in the context of lean.

Waste Category	Definition	References
Transportation	Unnecessary movement of materials, and tools this leads to increasing the cost and variability of the project.	[1,2,14,16,17]
Waiting	Much variability in the design processes leads to problems with activities flow that also end up with time waiting for the following processes with no adding values to the final product.
Overproduction	Producing earlier or more than client orders. (Unordered products). Thus, waste of resources, waiting, and inventory are the outcomes.
Defects	Producing parts that do not meet the client’s satisfaction. So, rework cycles and more resources are wasted to reproduce the product to meet specifications.
Inventory	Related to unnecessary material stores and work processes that lead to a lack of workspaces and additional costs.
Motion	Unnecessary movement of individuals or equipment that does not add value which could result in decreasing the productivity of the processes.
Extra processing	Unnecessary process steps to produce things exceeded what is needed by the client or defined by the project scope

Design waste from lean waste perspective

The most significant design waste causes and sources were compiled previously (see section 4.2), lean design waste items are grouped under the seven waste categories related to lean context as shown in Table 4.

Table 4. Lean design waste items.

Category of Waste Sources	Lean Wastes Sources of Construction Waste generated by design	Transportation	Waiting	Overproduction	Defects	Inventory	Motion	Extra Processing
Inappropriate supplying of informatio	Poorly defined waste reduction roles.		√		√
	Waste reduction strategies are not included in the contract.				√
	Missing waste reduction guidelines		√		√
	No waste reduction target setting.				√
	Delay in providing information in the late design stages		√	√	√	√		√
	Lack of necessary design information		√		√			√
	Unrespect for environmental requirements		√		√			√
Clearness, recognition, and Communication	The client is unaware of waste reduction advantages.		√		√
	Waste reduction is not a requirement among designers.		√		√
	Inadequate communication between project parties.		√		√			√
	Design changes by designers.		√	√		√		√
	Insufficient and incomprehensible project brief.		√	√	√	√	√	√
	The design doesn’t include client requirements.			√	√	√		√
	Delay in information flow.		√		√			√
	Design visualization is missing.	√	√		√
	Design complexity			√	√	√		√
	Difficulty in communication among different specialists.				√			√
Feasibility study	Inadequate feasibility studies.			√	√	√
	No waste management feasibility studies.		√		√
Coordination and accuracy	Limited early coordination among parties.		√		√			√
	Waste reduction strategies are not involved during design.		√		√
	Errors in design.	√			√			√
	Errors in construction drawings.	√			√			√
	Insufficient design quality and quality control.		√	√	√	√		√
Project users	Users rarely participate in the briefing process.				√
	Unrespect for users’ cultures.		√	√	√	√		√
	Several last-minute changes provided by the client.			√	√	√		√
Quality and Sustainability	Upgrading project facilities		√	√		√
	Bad quality for the selected materials.		√	√	√	√		√
	Unrespect for the complete project life cycle.			√	√	√		√
Value	Frequent value engineering changes.			√	√	√
Tech.Advan.	Insufficient response to technological advancement.		√	√	√	√		√
Regulations	Ineffective communications with the government	√	√	√	√	√	√	√
Design Expertise	Waste reduction is not a design priority.		√		√
	Lack of understanding of design waste causes.			√	√		√	√
	Selected materials are not available on the market.	√	√		√		√	√
	Not design to standard material sizes.		√	√	√	√		√
Cost	Limited fees		√
Time	Inappropriate design timeline		√
Unforeseen Conditions	Sudden conditions	√	√		√		√	√
Mar. cond.	Insufficient response to market condition		√	√	√	√		√

‘Source. Authors after [3–7,13–16]’

Identifying design waste items under the seven waste categories related to lean, explains the expected output and the embedded waste that could occur in the construction processes [15] such as rework that happens due to insufficient cooperation [1,2]; transportation, and motion in the construction site due to the poor logistics design [6]; waiting due to missing resources or data [14,15]; extra processing, overproduction, and inventory because of inadequate planning procedures [16,17,20]. Waste identification is considered the first step that allows waste reduction to occur through improving the workflow and process efficiency and achieving perfection with the support of different lean practices [21].

How lean can help in construction waste reduction from early design phase

Lean is divided into five main elements: value, value stream mapping, flow, pull, and perfection [17,20,21]. It goes beyond production management principles that achieve waste reduction, and customer satisfaction [6]. It focuses on value-adding activities and value streams aiming to reach perfection, granting reliability in the project delivery phase, and bringing off continuous improvement [7,14].

Lean procedures for construction waste reduction from the early design phase

Many studies [17,22,23] have indicated that the principles of the lean concept in waste reduction can be briefed in the following tips:

• Achieving a balance between flow and conversion activities.

• Minimising the portions of non-value-adding activities.

• Setting up a benchmark.

• Maximising the value of output by establishing a systematic approach related to client needs.

• Fulfilling continuous improvements in the design phase.

• Diminishing variability that could occur in the design phase processes as much as possible.

• Focusing on the completion of the design phase processes.

• Clarifying the various processes and parts.

• Rising with transparency.

• Increasing the flexibility of the outputs.

Lean procedures for construction waste prevention from early design phase

Several lean tools are referred in the literature to prevent waste from the early design phase such as:

• Pull technique is an efficient procedure that works based on supplying only the exact quantities due to the project requirements [2,22]. The implementation of this procedure prevents waste and guarantees adequate planning for all the activities in the project [23].

• Mistake proofing is a procedure that is specialized in improving the performance of the project by minimizing the time of certain tasks to save it for critical activities [23,24].

• Process analysis is a well-known lean procedure to prevent waste in a way that develops special criteria for the organization including qualifications and standards associated with waste reduction guidelines [14,22]. Also, this tool can identify analysis strategies that avoid waste from the very beginning of the construction project [24].

Impact of construction waste reduction from early design on sustainability

Many challenges face sustainability which stem mainly from the necessity of balancing the main sustainability pillars namely economic, social, and environmental issues [6,7,17]. One important starting point for improving the strategies that support sustainability is to enhance the chances that currently use the best practices [18,22]. For example, the lean concept tackles sustainability challenges and is adapted to fit sustainability requirements [22]. Hence, various publications have described the influence of lean methods and practices on different pillars of sustainability. For instance [25], indicated that applying lean to reduce waste provides perfect conditions to implement sustainability initiatives to reduce waste associated with the consumption of energy, natural resources, or water. Additionally, waste reduction of lean design aims to line up with good environmental practices. For example, waiting is one of the seven wastes tackled by lean context [17]. In this case, when this waste is reduced or eliminated, it does not only reduce operational costs but also the unnecessary consumption of energy that might be used in cooling, heating, and lighting during the design phase [22]. Table 5 lists the benefits that could be gained by organizations related to finance, environment, and social aspects when reducing the seven lean wastes.

Table 5. Impact of waste reduction on sustainability.

	Benefits	References
Transportation	Reducing transportation leads to reducing energy usage, emissions, and cost.	[26]
Waiting	Reducing waiting can accelerate the phase of design. Thus, less energy will be consumed in cooling, heating, and lighting during the design time.	[22]
Overproduction	Reducing the unnecessary parts will lead to less usage of raw material, energy to operate, and the risks of not using these parts	[26]
Defects	Reducing defects means that there is less energy consumption that is used to produce or recycle defective parts.	[21]
Inventory	Reducing inventory means that organizations can use the spaces efficiently for necessary demands, less consumption of raw materials, and decrease the risks associated with obsolescence and undiscovered defects.	[27]
Motion	Reducing motion means that the distances which must be taken by employees are less which leads to improving the human factor and minimizing the consumed energy.	[22,27]
Extra processing	Improving the processing means that there is a cut down on waste and minimizing the negative impacts on the environment.	[23]

As a proven consequence, when reducing waste using lean thinking, the quality, and efficiency of design activities are improved, while time and cost are minimized [6,21]. The implementation of lean design techniques and procedures to reduce waste is crucial to create a productive and sustainable working environment [22].

“Resources and material” waste reduction from early design phase

Green Building Rating Systems (GBRS) are useful tools to evaluate whether a building is environmentally friendly or not. They can serve as guidelines for assessing the performance of a particular building in its different phases. Generally, they contain different main categories, including energy, water, indoor air, and resources and materials, etc. Construction waste management principles and related items are included and the benefits of avoidance (i.e. reduce, reuse, and recycling) options are recognized in the ‘Resources and Materials’ category. This paper tackled ‘Resources and Materials’ category’s related items from LEED (Leadership in Energy and Environmental Design) as it currently considered to be a leading GBRS worldwide. The choice of LEED system over others is simply based on researches gathered and interpreted [1,28].

Relationship between “lean wastes” and “resources and material”

The main objective of ‘Resources and Materials’ category in LEED is to guarantee best practice for resources consumption in terms of materials. The category mainly concentrates on the reusability and maintenance of construction materials. It also addresses construction waste reduction, where this reduction not only rely on waste management plans that are implemented for demolitions, reuse of materials and products and recycle back the waste materials to the manufacturing process but also encourage the reuse of part of existing building [3,18].

As mentioned before in Table 5. Identifying lean seven wastes in the construction environment is the first step in the lean implementation process to reduce waste. Table 6 illustrates the relationship between different wastes defined in lean construction and their relationship with ‘Resources and Materials’ sustainability’s parameter. Lean wastes of overproduction and extra-processing directly result in resources and material waste and could lead to additional raw material extraction due to the producing unrequired quantities or components. Also, waiting waste could indirectly affect the resources and material. For example, concrete in transit mixers waiting to be poured and structural elements waiting to be installed could deteriorate with time leading to resources and material waste. Defects lead to rework which might need to be abandoned or rectified. They cause direct resources and material waste due to raw material loss. Similarly, excessive inventory could lead to improper storage and space constraints which directly affect the resources and material due to spillage or deterioration [7]. Therefore, identifying wastes from early design as defined by lean construction and making efforts to reduce them will have a positive influence on the sustainability in the construction sector. The following section deals with the application of lean design principles with the help of various tools that are adapted in the background of lean philosophy in order to reduce ‘Resources and Material’ waste [12].

Table 6. Relationship matrix between lean wastes and sustainability impacts related to ‘resources and material’ waste.

	Resources and Material Waste Generation
Transportation		-
Waiting		Indirect
Overproduction		Direct
Defects		Direct
Inventory		Direct
Motion		-
Extra processing		Direct

’Source. Authors after [7]’

“Lean design” for “resources and material” waste reduction from early design

While design is a phase that incorporating various construction techniques and materials to produce value to a client. It is important to note that considering the effects, the design has on the overall life of a facility is very crucial. Design of a sustainable construction project is especially decisive because green materials, resources and construction technologies require comprehensive coordination for the best performance in green facilities [25].

Lean design is an approach that aims to reduce resources and material waste during the construction of sustainable facilities. Its contribution to waste minimization originates from its focus on optimizing resource utilization [8]. Several lean design methods could be implemented in the project to reduce the material waste as follows:

- Integrated Design: is one of the most important methods for sustainable construction as it encourages architects and designers to integrate various green materials and construction technologies in the early design phase. Also, it ensures their necessity to reduce using energy and other resources which maximize the sustainability of the project [6].

- Just-in-time (JIT): considered as environmentally-friendly method as it reduces the various sources of extra material inventory because it works on the concept of delivery of materials, information and drawings, or any input required for a project to the point of usage. Many advantages and long-term objectives are the outcome of using such method. These benefits are inventory reduction, reduction of costs and reduction in the timeline of projects which lead to enhancing the productivity of the construction industry and achieving sustainable built environment [1,2].

-Kaizen: is an intensive and focused approach to process improvement in the workplace that helps to waste reduction by defining tasks for responsible parties, time, and tools to uncover areas for improvement and to support change which leads to efficient use of resources [4].

-Value Stream Mapping (VSM): identifies the flow of both information and material needed to achieve the project, the way value is recognized and establishes when and how the decisions are necessary to be made. Also, it maximizes the performance during the design phase through establishing choices to the surface and finding alternatives. Furthermore, maps are provided in project level and then analyzed to better investigation on how the design, material and resources work together to support customer value [7,12].

- Prefabrication: is the process of making the construction components in a place different from construction site. It is considered one of the most successful lean methods for resources and material optimization as it enhances the supply chain integration of green materials, Another advantages of using prefabrication related to economic pillar of sustainability such as; reduce the cost of prefabricated units when comparing with on-site units, reduced overall life cycle cost and enhanced flexibility and adaptability. In addition, there are benefits related to the social aspect of sustainability which is represented in a safe working environment [14].

“3 R s” for “material and resources” waste reduction from early design

To achieve the mission of sustainable construction, a lot of countries are looking forwards accomplishing the balance between developing the built environment and saving the natural resources as sustainable construction is not only focused on environmental aspects but also on economic and social aspects. This balance can only be reached by changing the traditional way of linear production process into a cyclic one that depending on the 3Rs method of reduction, reuse and recycle of material waste [12,13]. This strategy aims to guarantee best practice for resources consumption as far as materials. Furthermore, it improves waste management in construction as follows:

• Reduce: Reducing waste generation factors starting from early design phase may perhaps be helpful in the construction industry. It is a process that aims to reduce environmental destruction and the cost of construction. Nevertheless, minimizing the use of resources from the beginning of projects and reducing transportation work [1,3].

• Reuse: reusing material waste intending to prevent material waste from entering the landfill, reuse needs fewer resources, less energy, and less labor when comparing with manufacturing new products from raw materials [8,13].

• Recycle: recycling of material waste plays an important part in waste management plans. This obtains the reprocessing of material waste into a usable raw material or product thus, extending material life in addition to reducing resources consumption and avoiding disposal costs [21].

Managing landfill waste and long-term negative environmental economic and social impacts of material waste are now becoming very important for the sustainable construction. Thus, identifying waste root causes from the early design phase and progress in moving toward lean and sustainability is considered essential and cannot be overemphasized.

“Designing out waste” for “material and resources” waste reduction from early design

Waste reduction must be an essential part of the sustainability agenda from the early design phase by implementing the principles of designing our waste strategy. This strategy explained the resource usage efficiently by reducing the generation of waste from the early design phase and identifying how to be reduced [29]. The UK waste and resources action program that originated this strategy to reduce waste from the early design phase has promoted five main principles [28] which are summarized in Table 7.

Table 7. Designing out waste strategy principles.

Designing out waste approaches	Description	References
Design for Waste Efficient Procurement	- Identifying the root causes of reused substances and materials. - Minimizing the packaging that is used for materials Procurement. - Ensuring the logistics of material delivery within the needed time	[29]
Design for Materials Optimization	- Concentrating on the minimum material usage from early design. - Promoting the use of local materials. - Defining recycling criteria. - Focusing on building maintainability. - Replacing defective parts throughout the building life cycle.	[29]
Design for Off-Site Construction	- Using prefabricated building parts. - Using off-site elements, modular volumetric construction, and pre-cut building components	[16]
Design for Reuse and Recycling	- Re-entering construction materials and parts in the production chain. - Evaluating, if any existing building parts on-site such as windows, tiles, and bricks could be partly or completely reused. -Identifying the adjustments to these components to fit the project needs.	[9]
Design for Deconstruction and Flexibility.	- Considering maintenance and refurbishment as priorities. - Identifying material recovery strategies during the life cycle of the building.	[30]

Design activities that focus on efficient usage of resources to cut waste from construction projects which in turn leads to achieving different sustainability objectives is the clear definition of designing out waste strategy [28,29]. These activities are added to the final matrix for construction waste reduction from the early design phase as an explanation for sustainability’s crucial role in increasing the performance of waste reduction plans from the early design phase.

Discussion and conclusion

Matrix for construction waste reduction from the early design phase

A matrix for construction waste reduction from the early design that integrates lean and sustainability best practices is presented in Table 8 in order to consistently increase the performance of the waste reduction plan and ultimately lead to balanced performance improvement in terms of environmental, social, and economic aspects.

Table 8. Matrix for construction waste reduction from the early design phase.

Category of Waste Sources	Design phase stages Course of action	SD	PB	CD	SC	TD
Clearness, recognition, and Communication	Identifying waste reduction advantages to the client	√	√
	Considering Waste reduction strategies as Design Priority		√	√		√
	Providing adequate communication between project parties using the last planner system (LPS) lean technique	√	√			√
	Minimizing design changes by designers as much as possible		√	√		√
	Providing sufficient and comprehensible project brief.	√	√	√		√
	Involving clients at the early stages of the design	√	√
	Including all the client requirements in the design	√	√	√
	Efficient information flow.	√	√	√	√	√
	Providing Design visualizations.		√	√
	Simplifying the design.		√	√		√
	Establishing training programs to promote the realization and the technical skills of responsible parties			√	√	√
	Granting efficient communication among specialists.		√	√	√	√
Appropriate supplying of information	Well-defined waste reduction roles.	√	√
	Including waste reduction strategies in the contract	√	√
	Providing waste reduction guidelines	√	√
	Setting waste reduction targets.	√	√
	Providing information from the early design stages	√	√	√	√	√
	Providing all the design information	√	√	√	√	√
	Focusing on environmental requirements	√	√			√
Coordination and accuracy	Providing early coordination among parties.	√	√	√	√	√
	Involving Waste reduction strategies during design.	√	√	√	√	√
	Minimizing design errors as much as possible			√	√	√
	Minimizing errors on construction drawings.				√	√
	Providing sufficient design quality and quality control.		√	√		√
Design Expertise	Understanding design waste causes.	√	√	√		√
	Considering maintenance in design decision making	√	√
	Choosing designers based on their experience regarding sustainability	√	√
Project users	Participating of project users in the briefing process.	√	√
	Importance of respect for users’ cultures.	√	√
	Minimizing several last-minute changes provided by the client.	√	√	√	√	√
Quality and Sustainability	Minimizing upgrading project facilities if it is not crucial	√	√	√		√
	Respect for the complete project life cycle.	√	√	√		√
	Focusing on procedures related to energy savings and environmental issues	√	√	√		√
	Applying lean construction management for achieving sustainability			√		√
	Using 5s and error-proofing lean techniques to develop health and safety considerations for employees.				√	√
	Reusing building facilities			√	√	√
	Reusing demolition parts		√	√		√
	Identifying recycling criteria		√
	Using precast steel frames			√
	Encouraging the commitment of top management to sustainable waste strategies			√		√
Feasibility study	Providing adequate feasibility studies.	√	√
	Providing waste management feasibility studies.	√	√
Value	Minimizing the frequent value engineering changes.	√	√	√	√	√
Resources and Material	Good quality for the selected materials.		√			√
	Using local material.	√				√
	Rapidly Renewable Materials	√				√
	Using certified wood	√				√
	Choosing reusable and sustainable materials.		√			√
	Design a storage to collect recyclables					√
	Using material waste reduction strategies such as 3Rs – Reduce, Reuse, and Recycle				√	√
	Ensuring that the selected materials are available in the market		√			√
	Reusing existing materials			√	√	√
	Recycling used materials			√	√	√
	Design to standard material sizes (Standarisation)		√		√	√
	Design to Prefabrication		√		√	√
	Adopting the “just-in-time” lean technique to reduce material supply delays.		√		√	√
Technical Advancement	Efficient response to technological advancement.		√		√	√
	Offsite prefabrication elements and structures					√
	Considering new technologies for design based on cloud computing such as BIM		√			√
Regulations	Efficient communications with the government	√	√	√	√	√
Cost	Unrestricted design fees	√	√
	Controlling the payment schedules to ensure that companies get paid on time.	√	√
Time	Appropriate design timeline	√	√	√
Unforeseen Conditions	Preparation plans for reducing waste result from weather conditions	√	√	√	√	√
Market Condition	A sufficient response to market condition	√	√	√		√
	Supervising price changes in the construction material market	√	√	√	√	√

’Source. Authors after [3,4,6,12,13,15,16,18,20,22,30]’

This matrix for construction waste reduction from the early design phase includes the courses of action for the different identified sources that are responsible for construction waste generation from the early design phase using lean techniques and sustainability strategies. It is important to note that the matrix arranges the sources of waste based on their importance according to the high number of design wastes’ causes each category contains related to Table 2. For example, ‘Clearness, recognition, and Communication’ is the most important waste source as it contains 24% of design wastes causes and so on. The implementation of this matrix can generate favorable outcomes on the different sustainability pillars.

Benefits of the matrix

The matrix can contribute to enhancing design phase activities that serve the waste reduction issue by integrating courses of action that minimize construction waste generation from the early design phase using sustainability and lean concept implementation. The benefits of the matrix lie in explaining what the steps are to be taken by architects in different stages of design namely strategic definition, preparation and briefing, concept design, spatial coordination, and technical design to control the deficiencies of the traditional design phase and identifying the challenges facing the construction waste reduction from early design using efficient lean techniques and sustainable designing out waste strategies. This correlation presented in Table 8 promotes client value and achieves sustainability objectives through improving the living conditions of the society, focusing on the surrounding environment, and increasing the economic aspects.

Results show that this study confirmed the results of studies applied in different countries: integration of lean and sustainability from the early design phase in the issue of waste reduction, achieves efficient outcomes; this includes but is not limited to resource management, energy minimization, elimination of non-value-added activities, and health and safety improvement.

This research explores relationships between lean and sustainability on the issue of waste reduction from the early design phase. Many previous studies encouraged the implementation of lean and sustainability integration in the issue of waste reduction from the design phase to the completion phase of a project, involving all construction stakeholders holistically to guarantee an optimistic flow of activities [17,18]. The overall conclusion of this research is compatible with the same studies worldwide, which are focused on waste reduction as a common and highly considered characteristic in both philosophies of lean and sustainability and its impact on project value and cost reduction which increases productivity and continuous improvement [6,16,18,20,29]. According to that, many conclusions can be derived from the research discussions and analysis, these are:

1. Causes of Construction Waste generated in the design: Results show that there are some important sources, designers must take care of since they have a high number of causes. The first source of waste is ‘‘Clearness, recognition, and Communication” with a higher value as it contains 24% of design wastes causes, then ‘Inappropriate supplying of information’ with a value of 17%, ‘Coordination and accuracy’ & ‘Design Expertise’ with 12% and 10%, respectively [3,6,14,15]. However, ‘Value’, ‘Technology Advancement’, ‘Regulations’, ‘Cost’, ‘Time’, ‘Unforeseen Conditions’ and ‘Market Conditions’ are the less important sources of waste generation. They have less amount of design sources that are responsible for generating waste in construction. (See Table 2.) [4,7,13,14,17]. Implementing lean and sustainability integration matrix could eliminate waste by controlling these sources through adopting lean & sustainability tools and techniques from the early design phase.

2. Results indicate that design waste sources are affected the most by a wide practice of embedding waste reduction strategies in the ‘Preparation and Briefing’ and ‘Technical Design’ stages when comparing with the other design stages [6,7,15,16,18,20,29]; waste reduction target setting and a good understanding of design waste causes by designers; influenced by efficient coordination and communication between project members; and facilitated by adequate waste reduction feasibility studies and material optimization.

3. ‘Last Planner System’, ‘Design Visualization’, ‘5S Process’, ‘Error Proofing’, ‘Standardization’, ‘Just in Time’, ‘Integrated Design’, ‘Kaizen’, ‘Value Stream Mapping’ and ‘Prefabrication’ are the most applicable lean tools that aim to reduce waste [1,2,4,6,7,14,17,21,23,27]. Risk management is not applied appropriately in the integration of lean and sustainability for construction waste reduction from the early design phase despite its well spread in the construction industry. Improving project management systems and expanding the use of risk management systems in buildings can lead to reducing inventory waste and rework [7,20].

4. Courses of Actions for Waste Reduction: The literature divided three groups of expected sources of actions in adopting the construction waste reduction from the early design phase [3,15,20,29]’’. The major expected sources of actions are economically related followed by environmental actions and at the last level comes the social actions [4–6,10,13,16,23,24]’’. It can be concluded that researches need to focus on social actions because of their greater return on all responsible parties in the construction projects, who can achieve environmental and economic benefits.

5. Results reveal that project stakeholders particularly architects, designers, clients, and developers are responsible for implementing best practices for waste reduction at source from the early design phase [5,7,11,17,19]. However, it can be concluded that researches need to concentrate on the efficient role of contractors in identifying the decisions related to waste reduction processes. This could in turn contribute to an efficient improvement in the current attempts to curb the rapid and significant pace of the levels of construction waste generation from the early design phase [11].

Finally, the conclusions of this study comply with the conclusions of the previous studies that were applied in terms of the importance of increasing the performance of the waste reduction plan in construction by identifying the sources of design waste to achieve positive outcomes in terms of environmental, social, and economic dimensions. This study recommends implementing the integration of lean and sustainability from the early design phase to help the industry move away and solve many problems related to waste reduction. Also, to guarantee the efficient achievement of lean and sustainability integration in the early design phase related to waste reduction methods that offer the potential for greater returns, Designers and other responsible parties must have deep knowledge of waste reduction strategies and tools of their practical applications.

It is expected from this study to serve as a benchmark for continuous improvements in the performance of the construction industry. Although the data required for the study were collected from different researches related to various countries, the study findings are generalized and are not categorized according to the country. Apart from this, there is a requirement to study the developed matrix on this relation in different cultures to enhance their generalizability and make adequate methodological and validation adjustments that consider the context and the design and construction characteristics of projects related to various countries and cultures. Furthermore, the level of significance of each of design waste source can differ from project to project depending on company size, project type, geographical, and weather conditions.

Despite the contributions brought by this study, there are limitations in the research, primarily related to being just a theoretical overview that investigated English data only, published between 2018–2023. Future studies can examine the effects of design strategies on the reduction of construction waste throughout the building lifecycle stages, integrated lean tools, and designing out waste techniques. Furthermore, it is required to apply the matrix of construction waste reduction from the early design phase in real-world situations.

Disclosure statement

No potential conflict of interest was reported by the author(s).