The Risk of Implementing Green Retrofitting in High-Rise Buildings Based on Work Breakdown Structures to Improve Quality of Resource Planning and Cost Accuracy ^†

Abstract

The building sector accounts for more than one-third of final energy consumption worldwide. Green retrofitting, which is part of the green building activities, is one of the main factors in achieving the target of zero carbon emissions by 2060. Green retrofitting is a viable way to reduce greenhouse gas (GHG) emissions and energy consumption. The risks in green retrofitting work activities have not been studied much, even though the risks in green retrofitting projects are likely to be greater and more complex than the risks in conventional projects. This is reflected in the small application of customization in developing countries, one of which is Indonesia. Through the calculation of the risk matrix between probability and impact, a high risk was obtained from the relationship between risk and correlated resources, and it had a positive impact on the work breakdown structure (WBS). The results obtained show that complexity factors consisting of labor, materials, equipment, work activities, work methods, and scope/work package affect the success of the project, then the risk handling strategy that needs to be implemented is to set the right priorities. A focused project team allocates resources wisely. Knowing the probability of events and impacts arising from the non-implementation of the WBS, we identified sources of risk factors and high risk in the implementation of green retrofitting work based on the WBS based on the Greenship Existing Building Rating Tools and PUPR RI Regulation Number 21 of 2021 applicable in Indonesia, its effect on resource planning, and cost accuracy.

1. Introduction

Climate change is one of the issues that is currently of concern to all parties globally. The concept of ’Net Zero’ is now commonly stated as a global action to combat climate change and carbon emissions that has been agreed upon by many countries. To date, more than 100 local governments and 800 cities have agreed to Net Zero by 2050 targets to achieve the global goals in the Paris Agreement, pursuing a temperature reduction below 2 °C to limit temperature rise to 1.5 °C [1].

Based on the World Green Building Council report in 2021, the high operational and maintenance costs of existing buildings hold 75% of greenhouse gas (GHG) emissions [2]. According to the Love and Bullen report, most conventional buildings will remain in use for the next 50–100 years based on the aged design of the buildings [3].

Therefore, green retrofitting or renovating existing buildings is a viable way to reduce GHG emissions and energy consumption. Green retrofitting has also been proven to be more beneficial for the environment than demolition and building new buildings [4], because the demolition process will produce large construction waste; on the contrary, green retrofitting will minimize construction waste and use fewer material resources [3].

Retrofitting the energy efficiency of existing buildings plays an important role in achieving sustainable development because the number of new buildings per year only increases slightly. Meanwhile, the reality is that in developing countries, most existing buildings are not energy efficient because they were built with designs and technologies that are not energy efficient [5]. Green retrofitting of existing buildings is an effective way to make changes in the performance of existing buildings to achieve low energy consumption and low carbon emissions [6]. The benefits of green retrofitting include operational cost savings, quality assurance, better air and environment quality, and changes in work quality [7]. Based on the NZE Roadmap 2050, the target of reducing carbon emissions from the building sector by 51% and reducing carbon emissions for 2050 is targeted at 97% [8]. The world’s green retrofitting target until 2050 is 2.5% per year. If it is less than that number, the level of energy demand will increase, and more efforts will be needed to achieve the target of zero carbon emissions by 2050 [8].

In its implementation, modification (green retrofitting) requires a large investment, is complex, and is associated with many risks [9]. In addition, risk is also considered a critical obstacle to the development of sustainable construction worldwide [10], which is also the same obstacle for green retrofitting projects [7].

Most literature and guidelines related to cost estimation (including green building projects) still focus on estimates that are not directly related to the risks and uncertainty that can occur due to the effect of costs on green retrofitting projects, while literature related to risk and uncertainty is not adopted and implemented in the estimation or cost performance of green retrofitting projects [11]. The purpose of risk management in a green retrofitting project is not to avoid risks, but to make informed decisions, avoid unexpected cost overruns, time delays, quality degradation, and incidents, and apply appropriate decision-making to ensure the objectives of green retrofitting can be achieved [9]. Related risks must be identified, analyzed, and well managed through a comprehensive and complete risk management framework [9] by analyzing the risk factors (high risk) dominant in the source of risk studied and their effect on the resources and costs of green retrofitting work.

Previous studies discussed the risk analysis that occurs in the construction of green retrofitting projects and their impact on the performance of implementation costs. Green retrofitting can reduce the environmental impact of existing buildings but requires identifying critical success factors for successful implementation [3].

This phenomenon is understandable because green retrofitting buildings adopt high technology, green materials, and new procedures that are different from conventional buildings, so the risks associated with green retrofitting projects are likely to be greater and more complex than the risks in conventional projects [7].

In every project, work activity has an element of risk; the more complex a project is, the greater the risk that occurs [12]. The risks that exist in construction projects can affect the goals and objectives of each project activity. Project activities are descriptions of activity planning to complete project work packages [13]. Goals are something to be achieved, which objectives are specific and measurable actions that need to be taken to achieve goals. The two go hand in hand to achieve the desired result. Through the WBS, the goals and objectives of green retrofitting work activities will be described to identify the risks of implementing green retrofitting.

2. Literature Review

2.1. Retrofitting

Retrofitting is a cost-effective solution to create a better living environment by optimizing various building systems, to lower emissions and reduce energy waste [14].

According to PUPR Minister Regulation Number 21 of 2021, retrofitting is an effort to adjust the performance of buildings that have been utilized to meet the Bangunan Gedung Hijau (BGH) [15]. Retrofitting is also considered an effective strategy to improve the sustainability of existing facilities [3]. According to the U.S. Green Building Council (USGBC) [16], green retrofitting is defined as any type of improvement to an existing building wholly or partially occupied to improve energy and environmental performance, reduce water use, and improve comfort and space quality in natural lighting, air quality, and noise/noise pollution, done in any way that is financially beneficial to the building owner.

2.2. Green Retrofitting Criteria and Benchmarks

In the certification process in Indonesia, there are Greenship Rating Tools issued by GBCI [17] to determine the results of achieving green retrofitting ratings, consisting of six aspects or criteria, namely, appropriate site development (ASD), energy efficiency and conservation (EEC), water conservation (WAC), material resource and cycle (MRC), indoor health and comfort (IHC), and building environment management (BEM) as shown on Figure 1. There is also a benchmark for green retrofitting based on PUPR Minister Regulation Number 21 of 2021.

Based on the Greenship Rating Tools, Existing Buildings, version 1.1, green retrofitting work is formulated in six credit categories that are deemed important issues to the environment and its residents by GBCI [18].

The Green Retrofitting Benchmark based on PUPR Minister Regulation Number 21 of 2021 states that the implementation stage for existing buildings includes the utilization and demolition stages. Performance assessment of the BGH utilization phase for existing buildings consists of BGH organization and governance, the retrofitting construction process, maintenance of BGH performance during the utilization period, and the role of BGH occupants/users. The performance assessment of the demolition phase consists of the parameters of the demolition procedure and efforts to restore the environmental site.

2.3. Work Breakdown Structure (WBS)

The WBS is a hierarchy of project scope that project team members must pay attention to in order to achieve project objectives and project deliverables.

WBS standards in PMBOK, among others [19], are as follows:

• Activity is a component of the work performed during a project.
• Apportioned effort is an effort applied to work that is not easily divided into discrete efforts for direct proportions to be measurable
• Control account is an integrated control point of scope, budget, cost, and schedule management.
• Task is a task or job placed in a WBS for various jobs.
• The WBS component is input data in the structure to define project-related activities.

So, the WBS can be used as a framework for managing work to completion [20].

The purpose of the WBS in general is to assist in the process of planning buildings, while the green retrofitting building WBS will assist in certifying and defining work activities based on available benchmarks. The creation of the green retrofitting WBS is expected to help project leaders, project members, and stakeholders in aligning the vision of the work on the green retrofitting project and producing the final product of green retrofitting development via the project objectives.

2.4. Risk Factors and Sources

About the project, risk can be interpreted as the cumulative impact of uncertainty that hurts project goals. Risk is the uncertainty of an event or condition that, if it occurs, has a positive or negative impact on the project. Risk comes from the uncertainty that arises in the project. Once risks have been identified and analyzed, then it will be planned to carry out a risk response [19]. A risk has a cause and, if the risk occurs, it will have an impact on the cost, schedule, and quality of the project [13].

Project risk is always present on construction projects and often affects project schedules and costs. Risks on projects are always something to pay attention to because of their effects, which can make projects late and cause cost overruns [21].

The failure in cost planning is due to the complexity and uncertainty of the project system [22]. In other words, the evaluation of project cost overruns has a lot to do with resource allocation inefficiencies and can help estimate possible future infrastructure risks [23].

In identifying risks, the use of the WBS categorizes work risks, starting from work packages, methods, work activities, labor resources, materials, and tools [24].

The definition of risk under ISO 31000 [25] is the effect of uncertainty on the target. The uncertainty may be positive, negative, or not as expected. So, in the implementation of activities and sources of risk, it is necessary to see whether the goals and objectives can be achieved if there are potential risks that may occur.

To determine the risks that will affect the cost of implementing green retrofitting, a WBS will be used. With the help of a WBS, each green retrofitting implementation activity can be identified and potential risks can be mitigated [26]. Also, if designed correctly, the WBS will help to achieve project objectives, namely, schedule compliance, cost, and project quality [27].

2.5. Resource Planning

Construction project resources are potential capabilities and capacities that can be utilized for construction activities [28]. Problems in a construction project can be avoided if the proportion of resource use is optimal. Construction project resources consist of several types, including cost, time, human resources, materials, and equipment used in project implementation. To utilize resources appropriately, a resource management system is needed [29].

Resources are an ability and capacity of retention that is utilized for human activities. Project resources consist of human resources, material resources, and equipment resources [30]. Resource planning is part of project resource management in PMBOK 6th edition.

Based on the 6th edition of PMBOK, the project resource management process begins with a resource management plan. A resource management plan is a process of determining how to estimate, acquire, manage, and use project teams and resources. This process undertakes efforts to manage project resources based on project type and complexity. Resource planning is used to define and identify resources to ensure resource needs are met during the project. Resources can be obtained from internal project assets or from outside the project through the procurement process. Competition for resource provision with other projects affects the project cost, schedule, risk quality, and other project areas.

2.6. Cost Accuracy

Cost accuracy is an estimate of the cost of a project, according to the actual cost incurred; in other words, measuring the extent to which the initial cost planning or budget reflects the actual cost. Cost accuracy is often used to evaluate control costs to match estimates. If cost accuracy is high, then initial cost estimates tend to be close to the actual costs incurred. However, if cost accuracy is low, then there is the potential that the actual costs could exceed the estimates.

Cost accuracy in the cost estimation process refers to the extent to which the estimated or projected cost corresponds to the actual costs that will be incurred at the time of project implementation. The level of cost accuracy is generally expressed in certain percentages or categories, and the more detailed the information on a project obtained during the estimation process, the more accurate the results of the cost estimation incurred. In the conceptual stage of the estimation process, cost accuracy is assumed to be +/− 30% [31]. According to Serpell [32], five factors affect the accuracy of estimates: scope quality, information quality, uncertainty level, estimator’s performance, and estimating procedure.

3. Operational Model

A research operation model is a framework used to organize, run, and analyze research, involving the selection of research problems, formulation of hypotheses, selection of appropriate methods for data collection and analysis, as well as interpretation of results. The operational model is the result of a performance analysis process and process system using the assumption that inputs through the process will be able to produce outputs. The output of this study is in the form of the most dominant risk factors in the implementation of green retrofitting in WBS-based high-rise buildings, which affect the performance of green retrofitting implementation, as seen in Figure 2.

A conceptual framework is needed in the research process to explain the flow of research. The conceptual framework is a framework for thinking about the relationship between variables involved in the research or the relationship between concepts and other concepts of the problem under study. The conceptual framework for this study is presented below.

4. Methodology

Risk identification is a reinstatement process because new risks can be recognized by project progress in the project lifecycle [20]. There are tools and techniques used at this stage to identify risks, namely:

• Delphi technique, which is a consensus of project risk experts facilitated by a questionnaire to get an idea of the dominant project risk, which is then summarized and recirculated for further comment. This technique helps to reduce bias in the data [13].
• Interviewing, a technique for collecting data about project risks, which is carried out with project team members and other stakeholders who have experience in project risks.
• Root cause identification is a technique carried out to determine the essential causes of risk. The main result in the risk identification process is the existence of a risk register, which is divided into risk ratings.
• Data were collected using an online survey instrument developed specifically for this study. The survey comprised both closed-ended and open-ended questions. The closed-ended questions employed a Likert scale to measure participants’ perceptions of risk associated with green retrofitting projects, while the open-ended questions allowed participants to provide additional insights and comments.

The research flow framework shows the process from the beginning of data collection and analysis to synthesis, which is a summary of various types of reference sources to the results achieved. The research methods used were data analysis, questionnaires and expert validation, archival analysis, Delphi analysis, and statistical analysis. Questionnaires were used for expert validation of differences and similarities in benchmarks/parameters of green retrofitting work, validation of the WBS content and structure constructs, pilot surveys, respondent surveys, and final expert validation. The data collected and analyzed produced output in the form of WBS standards on green retrofitting work to improve resource planning and cost accuracy. Figure 3 is the Result flow chart of this section.

The lack of knowledge between each construction industry stakeholder regarding the availability and need for green materials in the market can cause price fluctuations that can have a positive impact on project cost estimates in the event of a decrease in green material prices, resulting in significant savings for project cost estimates [7].

5. Results and Discussion

We identified the goals and objectives of each work activity based on the WBS benchmark for green retrofitting work in high-rise buildings based on GBCI and PUPR Regulation Number 21 of 2021, based on secondary data. Furthermore, we processed the goals and objectives related to each work activity in the WBS green retrofitting work based on literature study sources formulated based on work activities, providing statements about things that need to be done to meet the project objectives (work activities) that have been set, then improved based on input that has been given by experts.

Next, we identified the source of risk or risk factors of green retrofitting work. Identification of sources/risk factors was carried out based on literature studies from various sources and guidelines based on PMBOK 6th edition (2017), which adjusts each WBS level to the risks that can occur, namely, labor, materials, equipment, work activities, work methods, work scope/package, and work environment. Finding risks that have an impact on disrupting overall project performance can cause losses to costs, time, and quality of work [13].

Identifying the high risk of green retrofitting work at the research data collection stage, a survey of respondents related to the risk of implementing green retrofitting work was carried out through statistical analysis and mean methods to find the risk rating with the highest influence on cost accuracy and resource planning using the risk matrix PMBOK 6th edition (2017).

Furthermore, analysis was carried out using the mean method to find the average level of risk from respondents’ answers for each implementation risk variable.

5.1. WBS Level 5 (Activity) Relationship and Goals and Objectives

In PMBOK [19], it is explained that the process of making the WBS is a process that breaks project deliverables and project work into the smallest parts with more managed components. WBSs are designed to show how project deliverables can be broken down into work packages and provide a way to show areas of responsibility based on the levels.

According to the Project Management Institute [33], each level of the WBS will represent an increasingly detailed definition of project work, so that the WBS can be used as input for each process of making project schedules and budgets [34].

In making the green retrofitting WBS in six aspects, activities were defined based on three project cycles, namely, the planning, construction, and post-construction stages, which were based on the certification of Greenship Existing Buildings 1.1 GBCI [17] and PUPR Regulation Number 21 of 2021 [15]. As Shown in Figure 4, the following activity levels are:

• Level 1, green retrofitting,
• Level 2, project cycle,
• Level 3, type of job,
• Level 4, process methods and support,
• Level 5, job activities.

The creation of the green retrofitting WBS is expected to provide a framework for all deliverables in all phases of the lifecycle to meet project objectives in meeting the criteria for aspects of green retrofitting work [18].

Figure 4. Green retrofitting WBS framework, GBCI Development and PerMen PUPR [15,17].

Figure 4. Green retrofitting WBS framework, GBCI Development and PerMen PUPR [15,17].

5.2. Risk Relationship with Cost of Green Retrofitting Work High-Rise Building

Based on literature studies and previous research that discuss the risks of green retrofitting work for WBS-based high-rise buildings, the risks affect’s cost of implementing green retrofitting. So, we get variable X (independent variable) in the form of the risk of building a WBS-based green retrofitting project, which can affect variable Y (dependent variable), namely, resource planning and the accuracy of the cost of implementing green retrofitting.

Validation of the results of risk identification related to sources/risk factors was carried out by distributing questionnaires to respondents containing the frequency of occurrence and the impact/severity caused by these risks that can affect the estimated cost of implementing green retrofitting. The frequency level and impact/severity were filled in based on the measurement scale used to determine the dominant high-risk factor, sourced from the risk matrix in Figure 5 [19], which describes the level of risk (high, medium, or low) based on the frequency/possibility of risk and severity.

The predefined matrix for categorizing risk as high, medium, or low indicated the appropriate type of risk matrix, depending on the complexity of the project. The cumulative risk score was calculated by adding or multiplying the likelihood and impact values. Then, we compared risk ratings based on predetermined criteria and prioritized the risks that had the highest likelihood and impact. We created a plan to address the prioritized risks.

Through the table below, it can be explained that each value (1–5) related to the frequency of risk occurrence can be described.

Table 1. Risk probability index values [19].

Index	Value	Probability
Very High	5 (0.9)	Always happens
High	4 (0.7)	Frequent
Middle	3 (0.5)	Sometimes it happens
Low	2 (0.3)	Rare
Very Low	1 (0.1)	Very rare

summarises the main risk occurrence of this section.

Table 2. Risk impact index values [19].

Index	Value	Impact
Very High	5 (0.8)	Very detrimental
High	4 (0.4)	Big losses
Middle	3 (0.2)	Quite detrimental
Low	2 (0.1)	Small disadvantages
Very Low	1 (0.1)	Negligible losses

as shows addition, the severity of the risk from values 1–5 can be described:

5.3. WBS Risk Relationship with Green Retrofitting Work of High-Rise Building

According to the Project Management Institute, project risk management is a systematic process of identifying, analyzing, responding to, and controlling project risks, whereby risk management is carried out to increase the probability and/or impact of positive risks and to decrease the probability and/or impact of negative risks to optimize project success.

In construction projects, the use of human resources (foremen, handymen, and workers) must be taken into account based on their productivity in producing products according to requirements, so that labor productivity becomes the core of the analysis of labor resource needs and schedules [18].

Presents a summary of labor risks based on a literature review found by the authors that can affect the implementation of green retrofitting work. The main findings discussed in this section are shown in

Table 3. Resource risks of green retrofitting work.

Index	Value	References
Worker	Labor force does not have the skills to do work with special designs and features in the retrofitting process	[35]
	Lack of knowledge about green retrofitting work	[36,37]
	Lack of standardized labor costs related to green building works	[37]
	Workers are not familiar with the green materials used	[38]
	Lack of experience supervising green retrofitting projects	[38]
	Unclear job specifications	[39]
	No training for workers	[25]
	Low worker productivity	[39]
	Lack of communication and coordination of work	[39]
	Insufficient number of staff	[37]
Work Activities	Work sequences are not risk-based planned	[25]
	Installation not by specifications or drawings	[25]
	Workmanship not by procedures	[25]
	There was a change in the work sequence	[25]
	Not identifying the level of artificial lighting in the space	[13]
	Not specifying areas that are air-conditioned or not	[13]
	Not taking into account natural lighting in OOTV lighting	[13]
	Not using the latest technology/inappropriate use	[13]
	Not knowing the conformity of the project with the RTRK	[13]
	Late award of client contract	[35]
	Lack of coordination at the design stage	[35]

6. Conclusions

Based on the WBS risk relationship with green retrofitting work of high-rise buildings, it can be concluded that:

• Project complexity is one of the main concerns that affect project success, both directly and indirectly. The main reason is that complex projects cause difficulties in identifying clear goals and targets. Therefore, it is important to re-evaluate priorities for effective project management. By setting the right priorities, the project team can focus on what matters most and allocate resources wisely so that the relationship between risk and resources is correlated and has a positive impact.
• The availability and demand for green materials in the market can cause price fluctuations that can have a positive impact on project cost estimates in the event of a decrease in green material prices, resulting in significant savings for project cost estimates. Material price fluctuations can also be a risk if material prices soar far above predetermined price estimates, so continuous monitoring of green material market conditions is very important to improve the accuracy of green retrofitting implementation cost estimation so that the relationship between risk and implementation cost estimation is correlated and has a positive impact.

Goals and objectives of work activities based on the WBS benchmarks in green retrofitting work aim to ensure clarity of the project direction and objectives, estimate the resources needed, and enable project monitoring and control.

The results of high-risk identification affect the accuracy of implementation costs in green retrofitting work.

Suggestions that can be given are to create WBS green retrofitting guidelines that have been risk-based to maximize the level of accuracy of the cost of implementing green retrofitting work. A more in-depth analysis is also needed related to implementation risks that affect the planning of implementation cost accuracy.

Using the WBS helps to identify potential risks early in the project lifecycle, allowing for effective risk mitigation strategies. This approach enhances the quality of resource planning and cost accuracy, leading to the successful implementation of green retrofitting projects in high-rise buildings.