This section discusses the commitment indicators identified from an extensive literature review in relation to the second stage of the project, the design phase. These indicators will inform the development of the SDCTT-D tool to help project participants track their commitment in this phase. According to Kuprenas [
6], the project design phase is an early stage where project structure, features, major deliverables, and success criteria are designed to achieve project goals. Thyssen et al. [
7] argued that, in the design phase, the project architects and engineers must ensure that project drawings and documents contain space orientations, materials, and specifications aligned with the project owner’s vision and regulations. The commitment indicators revolve around best practices in three SD decisions—waste, energy consumption, and reduction of carbon emissions—where the best practices and indicators used in the design phase to achieve the selected SD decisions will be identified.
2.1. Commitment Indicators for Waste Reduction
The following paragraphs discuss the indicators included in the first SD decision trigger, waste reduction, in the design phase.
Ng and Xie [
8] argued that identifying the availability of allocated resources for the project is an indicator of the project designer’s commitment to reducing project waste. According to Ng and Xie, resource allocation is the condition and quantities of resources available to the project to help the designers manage the project materials. In support of this, Anshassi et al. [
9] highlighted that overlooking such information will cause issues during the construction and, ultimately, project failure in attaining the waste reduction goals. Chang and Tsai [
10] pinpointed that the designers must identify the resources demanded from the project design based on the project’s requirements of materials, equipment, and technology. In support of this, Anshassi et al. [
9] highlighted that, from the demands of the project resources, designers could specify the resource capacity (the resources that can be spared for the project from the organization) of the project to avoid wastage. Ng and Xie [
8] indicated that the resource gap could be identified from what the project design required and the actual resources available for the project. Chang and Tsai [
10] specified that identifying this gap helps project designers to close it by designing the exact number of resources needed for the project to prevent resource waste.
Agarwal and Prakash [
11] highlighted that an indicator of project designers’ commitment to reducing waste is the integration level of recycled and reused construction materials in the project design. According to Azari and Kim [
12], using those materials in the project conserves natural resources and reduces the materials sent to landfills at the project’s end. Agarwal and Prakash [
11] argued that the integration process starts by identifying the available reused/recycled materials in the market. Pressley et al. [
13] highlighted that involving contractors and suppliers in the project materials design is an essential step to attain their viewpoint regarding reused/recycled materials’ selection. Florez et al. [
14] specified that project designers must integrate the selected recycled/reused materials in the project design in a way that reduces waste and minimizes the use of virgin materials. Agarwal and Prakash [
11] argued that to ensure the efficiency of the designed project’s reused/recycled materials, conducting a material life-cycle assessment through simulation is essential. According to Pressley et al. [
13], this assessment helps identify the selected materials’ environmental impact from material extraction to its use and specifies to what extent using those materials can minimize project waste.
Liu et al. [
15] stated that using Building Information Modeling (BIM) during project design helps identify the exact resources needed for the project and prevents wastage. In support of this, Nikmehr et al. [
16] highlighted that employing BIM in the design process is an indicator of project participants’ commitment to reducing project resource waste. According to Lévy ([
17] p. 4), BIM is “an architectural software environment in which graphic and tabular views are extracted from data-rich building models composed of intelligent, contextual building objects”. Cao et al. [
18] highlighted that BIM helps professionals (in architecture and construction) attain insights into the project from the data to improve the design, building management, and construction. Liu et al. [
15] indicated that the first step in utilizing BIM in the project design is identifying the materials’ design elements that lead to waste reduction. Wei et al. [
19] argued that to effectively employ BIM in the design, collecting all the information regarding materials’ design elements (from previous projects and historical data) is an essential step in BIM analysis. Najjar et al. [
20] highlighted that materials information gathering via life-cycle assessment (LCA) is where the process of extracting raw materials, manufacturing, site transportation, installation, demolition, and recycling will be analyzed to evaluate the best materials selection regarding the environment. Byun et al. [
21] indicated that the information collected about material construction elements (LCA) could be used to integrate them into BIM software and analyzed to identify the project’s best design that reduces waste and minimizes the environmental impacts of the project. Antón and Díaz [
22] asserted that the integration of BIM with LCA materials’ performance at the early design phase enables BIM tools with a source of information to conduct a complete project LCA that improves the project environmental performance as well as the decision-making processes. Liu et al. [
15] argued that BIM enables designers to simulate architectural and structural design requirements through a BIM-based material analysis tool to make necessary adjustments to reduce project waste.
Sadafi et al. [
23] highlighted that incorporating flexibility into project design is an indicator of the project designers’ commitment to reducing waste during the project design phase. According to Gil and Tether [
24], design flexibility is a concept where techniques such as adaptation (one space with multiple functions without architecture alternating [
25]) and transformability (changing exterior and interior spaces [
26]) could be considered to bring resource-efficiency and flexibility into the project design. Ellenberger [
27] argued that buildings designed to change their functions over the project life-cycle reduce resource consumption, while Sadafi et al. [
23] asserted that incorporating flexibility into project design first requires identifying the design elements that can be altered into different forms of usage during the project’s life. Ellenberger [
27] highlighted that designers must specify the project’s architectural spaces for the selected design elements based on their functionality or ability to meet users’ needs with fewer restrictions. Gil and Tether [
24] specified that the adaptation of project spaces within project design should be allowed to accommodate the growing working space. Sadafi et al. [
23] argued that to maximize the effectiveness of design flexibility, designers need to conduct a risk analysis containing design changes to reduce wastage and compensate for scarce information at the design stage.
According to Bonnes et al. [
28], involving experts with experience in sustainability work to improve and expand the design team’s knowledge regarding waste reduction is an indicator of participants’ commitment to waste reduction. In support of this, Tabassi et al. [
29] pinpointed that including experts in the design team is to seek a professional opinion regarding green design practices and incorporate new design techniques to ensure waste reduction. Bonnes et al. [
28] highlighted that incorporating green expertise into the design team starts by identifying professionals with sustainable design experience to stimulate the design team to go beyond current practice. Boudeau [
30], meanwhile, specified that pre-qualifying the identified professionals based on their knowledge and experience in waste reduction is an essential step in expanding the design team. In support of this, Boddy et al. [
31] argued that project participants should choose the most suitable professionals with waste reduction experience from the pre-qualified list to be included in the design team, while Bonnes et al. [
28] indicated that the project design team must integrate the ideas and techniques from the chosen experts into the project’s design to ensure waste reduction.
Therefore, the commitment indicators discussed previously exhibit parameters in sequential order. For the purpose of this study, these parameters are considered as a reflection of the degree of project participants’ commitment to waste reduction in the design phase. Hence, the first steps of each indicator imply a low commitment, and the combination of all parameters indicates excellent commitment, as shown in
Table 1.
2.2. Commitment Indicators for Energy Consumption Reduction
The next commitment indicator set in the design phase is designated to be the energy consumption decision trigger.
Riesz and Elliston [
32] highlighted that incorporating renewable energy sources in the project design is an indicator of project designers’ commitment to reducing energy consumption. According to Li et al. [
33], renewable sources vary from solar, wind, and other alternative energies and help minimize fossil fuel usage to generate energy and reduce operating costs. Rani et al. [
34] argued that to include renewable energy sources in the project design, project participants must first identify the available renewable energy technologies in the market. Riesz and Elliston [
32] specified that the design team selects suitable renewable technologies that can be used in the project design from the available ones. Waal et al. [
35] pinpointed that the selected technologies must be integrated with the project design to achieve the desired energy reduction, while Rani et al. [
34] discussed that, to ensure the synergy of the designed renewable systems, the design team needs to use a dynamic simulation for the designed renewable energy technologies to maximize their effectiveness.
Whitmarsh et al. [
36] indicated that including experts with experience in energy reduction techniques within the design team is an indicator of the project designers’ commitment to energy reduction goals. In support of this, Brunsgaard et al. [
37] pinpointed that including experts in energy reduction within the design team helps them expand their knowledge and incorporate new design techniques to minimize project energy consumption. Sayigh [
38] argued that to include a new energy expert in the design team, project participants must first identify professionals with experience in energy reduction design techniques. In support of this, Brunsgaard et al. [
37] highlighted that project participants need to pre-qualify the identified applicants based on their knowledge, years of experience, and previous projects and select the most suitable professionals for the project. Sayigh [
38] specified that the design team must integrate the ideas and techniques that emerged from energy experts into the project design to ensure energy reduction.
Cemesova et al. [
39] stated that BIM could be used in the project design to reduce energy consumption. Yuan et al. [
40] argued that the usage level of BIM during the design phase is an indicator of project designers’ commitment to attaining energy reduction goals. According to Eleftheriadis et al. [
41], BIM tools can visualize building energy performance by using the information from the project energy system. Cemesova et al. [
39] pinpointed that BIM enables designers to develop various combinations of energy-saving designs and analyze different types of project equipment to predict energy efficiency and select the best alternative. In support of this, Gourlis and Kovacic [
42] highlighted that BIM is capable of optimizing the project design machines, electrical systems, and buildings shall achieve the desired energy levels. Schneider-Marin et al. [
43] indicated that incorporating BIM in the project design starts by identifying design elements of project systems and areas with a high potential for energy consumption. Schlueter and Geyer [
44] argued that collecting information regarding the selected design elements from historical data and previous projects to feed BIM software is essential to optimize project energy design. In support of this, Gourlis and Kovacic [
42] asserted that integrating the collected information into BIM software to analyze project systems over the project’s life cycle is vital to maximizing its use. Meanwhile, Eleftheriadis et al. [
41] argued that using the BIM analysis tool enables designers to select the best combination of energy systems and optimize project energy design by making necessary design adjustments to those systems to reach the optimal energy level.
Sun et al. [
45] highlighted that an indicator of designers’ commitment to reducing project energy consumption is to consider operation and maintenance factors for project energy systems and equipment to ensure energy reduction. According to Hassanain et al. [
46], those factors reduce systems maintenance and improve energy efficiency and are considered essential elements in reaching the project’s energy reduction goal. In support of this, Broughton [
47] highlighted that including those factors within project design starts by identifying information regarding accessibility, modularization, standardization, and machine maintenance of the selected project’s systems and equipment. Sun et al. [
45] argued that, apart from project systems and equipment information, seeking input from maintenance personnel is essential to include their viewpoints in project design and helps the design team ensure energy reduction durability. Hassanain et al. [
46] stated that the project design team must ensure that both operational considerations and energy equipment maintenance information are integrated into the project design to ensure its effectiveness. Further, Sun et al. [
45] specified that to maximize the integration of maintenance factors into the project design, designers need to use a simulation program to simulate annual loads and peak demands for project systems to identify maintenance reduction opportunities that lower energy consumption.
Eley [
48] argued that utilizing net-zero energy design in the project design is an indicator of the designers’ commitment to reducing energy consumption. According to Aksamija [
49], net-zero energy is an energy system design that balances the amount of energy used by the building with the amount of energy generated on-site through renewable power generation. Eley [
48] further pointed out that the first step to achieving net-zero energy is to ensure building envelope efficiency through double insulation and exceptional air sealing. Harkouss et al. [
50] highlighted that the design team must identify equipment and technologies with high energy efficiency in the market that suits the project’s purpose, budget, and building envelope, while Aksamija [
49] argued that the design team needs to select the best combination of the carefully chosen equipment and technologies to be incorporated into project design to achieve energy efficiency. Mazzeo and Oliveti [
51] highlighted that, to ensure maximum benefit of the designed equipment and technologies, designers need to run a building assessment through an energy simulation to model building energy with various design variables to predict building energy performance. In support of this, Mavrigiannaki et al. [
52] specified that this assessment helps identify which energy-saving measurements allow the project to achieve net-zero energy, specify which project areas have high energy consumption, and develop strategies to reduce them during the design stage.
Therefore, within each commitment indicator reviewed previously, there are specific parameters characterized as a series of actions. These parameters are reflected in this study as an indication of the degree of project participants’ commitment toward energy consumption reduction in the design phase, whereby the first steps of each indicator reflect a low commitment, and the amalgamation of all parameters implies excellent commitment, as shown in
Table 2.
2.3. Commitment Indicators for Carbon Emission Reduction
The final commitment indicator set in the design phase is designated to fulfill the carbon emission reduction decision trigger.
De Medeiros et al. [
53] emphasized that expanding the design team’s knowledge in the field of carbon emission by involving experts in carbon emissions reduction design is an indicator of project participants’ commitment to carbon reduction goals. Ho et al. [
54] highlighted that expanding the design team starts by identifying professionals with carbon reduction expertise to stimulate the team and go beyond the current design practices. De Medeiros et al. [
53] argued that, according to the specified professionals’ resumes, the design team must recruit pre-qualified applicants based on their experience in carbon reduction. Lu et al. [
55] asserted that the design team needs to select the most suitable carbon reduction experts for inclusion in the team, while Ho et al. [
54] specified that in order to involve carbon experts in the team effectively, their suggested design ideas must be integrated into the project design.
Changhai and Xiao [
56] argued that using BIM computer modeling to reduce carbon emissions in the project design is an indicator of the designers’ commitment to the carbon reduction goal. In support of this, Xu et al. [
57] highlighted that BIM helps the design team run different simulations by changing project materials, systems, and machines’ selection and using their carbon data to check carbon emissions according to the simulation’s results. According to Changhai and Xiao [
56], using BIM for the project design first requires identifying the design elements with high carbon emissions. Eleftheriadis et al. [
58] stated that collecting necessary carbon data, whether from previous projects or manufacturing data, is an essential step in running BIM software effectively. Gan et al. [
59] emphasized that the collected data must be run through BIM to analyze project-designed materials, systems, and machines over the life cycle to identify the project’s carbon emissions. Galiano-Garrigós et al. [
60] argued that BIM tools enable designers to optimize project carbon design from materials’ and energy systems’ selection and make necessary adjustments that reduce project carbon emission.
Lai et al. [
61] pinpointed that there is a strong relationship between carbon emission and energy generation, where increasing energy generated from traditional methods leads to an increase in carbon emissions. In support of this, Adams and Achiempong [
62] highlighted that incorporating renewable energy sources (such as solar and wind power) in the project design is an indicator of designers’ commitment to reducing project carbon emissions. Nguyen and Kakinaka [
63] argued that the first step to integrating renewable energy sources and technologies into project design is to identify their availability in the market. Schandl et al. [
64] posited that the project design team selects suitable renewable technologies from the available ones to be in the project design and achieve the desired carbon emission level, while Wang et al. [
65] specified that the selected renewable technologies must be integrated into project design to reduce emissions. Further, Nguyen and Kakinaka [
63] indicated that to ensure renewable technologies are integrated into the design, the project design team needs to run a dynamic simulation to check total carbon emissions and optimize the technologies’ design by changing the selection of renewable technologies.
Ubando et al. [
66] argued that minimizing the project design’s carbon footprint is an indicator of designers’ commitment to reducing carbon emissions. According to Fabris [
67], a design footprint is a process of evaluating and measuring the building’s carbon emissions associated with building materials, machines, and systems used in the design to anticipate project carbon emissions. Trovato et al. [
68] highlighted that to minimize project footprint, the design team must identify the project design footprint based on the design selection of project materials, equipment, and machines. He et al. [
69] specified that the collected information about the design footprint helps the design team specify the design elements with high carbon-reduction opportunities, and Xiao et al. [
70] asserted that the design team must select different alternatives to the design elements with high carbon emission to refine project details’ design and reduce carbon emissions. Ubando et al. [
66] argued that to check the project design footprint, the design team needs to conduct a life-cycle assessment for the entire project design. In support of this, Xian and colleagues [
70] highlighted that this assessment considered all project flows (energy, materials, waste) in and out of the system to calculate project environmental impact, particularly carbon emissions.
Vuarnoz et al. [
71] argued that considering maintenance and operational factors for project machines and equipment during the design to minimize carbon emissions is an indicator of the project designers’ commitment to carbon reduction goals. In support of this, Monga and Zuo [
72] highlighted that incorporating those factors by the designers, guiding the project systems’ and machines’ selection process to choose the lowest maintenance of the systems and machines all reduce their carbon emissions. Schagaev and Kirk [
73] stressed that to incorporate maintenance factors into project design, the design team must first identify equipment and machine standards, modularization, and maintenance requirements to check their carbon emissions. Monga and Zuo [
72] specified that the design team needs to seek input from maintenance personnel regarding machines and equipment selection along with their maintenance information. Vuarnoz et al. [
71] stated that all collected maintenance information must be integrated into the machine and equipment selection process during the project design to ensure carbon minimization. Schagaev and Kirk [
73] argued that to ensure the integration of maintenance factors to project design, designers need to simulate the carbon emissions of the selected machines and equipment to determine the emissions profile and change their selection to achieve the desired carbon emission level.
Hence, the previously discussed commitment indicators contained parameters with sequential characteristics. In this study, these parameters are considered as an indication of the degree of project participants’ commitment toward carbon emission reduction in the design phase. Henceforth, the first parameter of each indicator reflects a low commitment, and the incorporation of all parameters reflects the excellent commitment, as shown in
Table 3.