Introduction

Buildings are irrefutably ‘living creatures’ that consume resources, generate wastes and emit carbon [1]. Even though these attributes importantly characterised buildings developed using the conventional practices or traditionally built structures, the metrics also depict the responsibility of buildings to the environment. Like ‘citizens of the city,’ buildings have ‘obligations to the society’ and constitute change agents that upset the ecosystem. Building is responsible for an estimated 40% of global energy uses and 50% industrial waste [2], so setting the construction industry at the crux of sustainability discourse. The implications of these outputs suggest that entrenching development practices with low environmental impacts and tackling holistically, construction related environmental problems would advance the sustainability of the constructed environment [3]. Buildings and their development practices are therefore, strategic to the sustainability of the constructed environment and the overall sustainable development [4]. Sustainable Buildings (SB) innovation contextualizes sustainable development praxis into the building sub-sector and set criteria for evaluating sustainability performance. This paradigm makes it possible to design, construct, maintained and operate buildings with less negative impacts on the environment [5].

SB methods and processes convey diverse tangible and intangible benefits [6]. However, the claims of enormous economic benefits do not include cost economy at the early stage. The studies that examined the potential strategies for reducing the First Cost (FC) of SB are inadequate amongst the growing research engagements in sustainable construction. Pertinent cost studies investigated the scope of extra costs along with regional levels [7, 8]. Even though traces of case studies have suggested that the cost of SB could be parallel or less than the alternate conventional construction approaches (ACB) using a set of interventions [9, 10], the overarching opinion reveals the high FC orientation is prevalent (Sustainable Buildings Market Study, SBMS, [11]). Even when certain improvement can bring about cost benefits, the beneficial strategies lack empirical grounding. The abysmal researching of mitigating strategies to lowering the costs of SB limits the ability to achieve economic sustainability goals in the construction industry [12].

As a result, the adoption of SB practices in developing countries and in the global perspective is seminally low [11]. Growing number of studies attributed low adoption of SB to high cost and lack of affordability [13, 14, 15, 16]. This study espoused strategies for First Costs Reduction (FCR) in the implementation of SB in developing countries (emerging markets) to improve their adoption. The study is a respond to the dearth of adequate inquiry on ‘theory, practice, metrics and policy consequences’ of seeking affordability in the pursuit of sustainable development in the construction industry [17]. The research problem is established on the gap that studies, which identified enabling policies to promoting SB adoption, are fundamentally unstructured [18]. The dearth of pertinent CR strategies so create difficulty in managing cost risks and uncertainties [19]. This study is therefore an economic sustainability agenda and the goal was to develop a structured lifecycle framework for achieving FCR in the implementation of SB. The study collected mixed data using three interdependent research approaches enlisting qualitative and quantitative strategies such as literature review, Delphi interviews and survey. These approaches were implemented sequentially to generate Cost Reduction Strategies (CRS), determine the significance of CRS and to validate the developed framework.

Theoretical development

Social practice theory

Social practice theory (SPT) stipulates that tasks are the focus of enquiry and not individuals [20]. Social practice as interactive behavioural activities, result from recurrent engagement with instructions and implementation of routine processes [21]. By extension to construction settings, SPT assumes that building development, their performance and uses are social practices; SB and FC are products of interactive social practices. Social contexts exist in this study (1) as a pillar of sustainability, (2) building is a social construct with multi-faceted interactions with the environment and (3) stakeholders and building practices connect through interaction [21]. Since routine engagements can improve practices through interaction and shared understanding, SPT is adapted to embed the study (Shove and Walker, 2014). The shared understanding demonstrates how to improved things (that is, FC) and the social purview means that the capacity of CRS to improve FC requires integration of practices, not individual orientation [20, 22]. The theory, by its extensive application in sustainability related researches, has demonstrated robustness to explain the decisions related to improvements in sustainable construction [21, 23].

Agenda for first cost reduction

Cost management profession research is under pressure to develop strategies to reduce the FC of SB development. The understanding suggests that diffused adoption of SB practices depends on the development of FCR strategies to optimise cost-effectiveness [24, 25, 26]. Mitigating FC would likewise expedite demand and supply of SB [27]. Empirical data emerging from exemplar SB projects are proofs that FCR is possible, since related developments are achievable with slight or no additional funding [10]. Data from the development of energy efficient buildings in New Zealand likewise showed that SB is achievable with cost economy [28]. CR in the context of this study denotes cost control mechanisms that can be implemented to achieve tangible reduction in the production costs of SB project [29]. This position clarified that CRS targets specific cost driver in the production processes and varies with project development stages (Kirham, 2014). Prompt and effective decision-making that optimises process improvement and innovation are also possible through mainstreaming of viable CRS [19]. This study argues that although the traditional cost management literature are not bereft of cost control mechanisms, the peculiarities of SB has created efficiency gap in the application of these models [2]. Innovative strategies are therefore expedient, amidst the seminal gap in dearth of structured framework for coordinating comprehensive CR activities across SB project development lifecycle.

The review of related literature shows isolated experimentation of various strategies to achieve FCR in diverse project settings across the globe, but a comprehensive framework detailing how new adopters can navigate SB implementation cost-effectively is not apparent. This study developed a structured lifecycle framework for achieving FCR in the implementation of SB. The agenda for CR in the context of SB and this study refers to a framework that outlines processes, guidelines, methods, approaches, controlling philosophies and procedures for accomplishing affordability objectives in SB development, using graphics and chart [31, 32]. Cost Innovation and Improvement Framework for Sustainable Buildings (CIIFSUB) is the agenda (implementation guide) for FCR in SB project development.

Material and Methodology

Two research designs (secondary data and survey) were implemented using three approaches, literature review, Delphi interview and survey. The Delphi study enlisted round-one semi-structured interviewing and round-two survey. Semi-structured interviewing engaged participants and experts in SB projects, design organisations and researchers with interests in sustainable construction in Nigeria. The interview generated CRS peculiar to SB implementation in the research environment. The selection of the interview respondents enlisted sampling by snowballing and progressed using three criteria: sustainability assessor’s status, team membership in SB projects and Doctoral studies in sustainable construction (Table 1). The interview procedure adopted the funnel technique and its five stages [33]. The preliminary enquiries conducted during the fieldwork revealed that 22 interviews were possible, but only nine response was obtained with a response rate of 41 percent. Interview data analysis adopted conversational scrutiny, the results added to the pool of data synthesised from the literature used in developing the framework.

The secondary data comprised research publications and reports of applied CRS in SB cases reported in the literature. This dataset emerged from the search of prominent databases using the search phrases such as (1) cost reduction strategies, (2) cost optimisation strategies, (3) cost innovation strategies, (4) cost improvement strategies, (5) framework for cost reduction in SB, (6) factors affecting cost of SB, (7) cost drivers of SB and (8) sustainability cost factors. The study conducted a screening of 62 resources retrieved from various sources for relevance and reviewed 28 papers and reports to generate the secondary data. Theoretical CRS and cost drivers from the literature were combined with round-one Delphi interview to produce the list of CRS ranked by experts in round-two Delphi survey to produce the significant CR strategies. Delphi study is appropriate for the research problem due to the dearth of quantitative evidence to show the significance of identified CRS [34]. The criteria underpinning the selection of the panel is likewise adequate [35] as well as the number of participants and number of rounds in the study [36].

Thirty-three (33) Experts (profile in Figure 1), using survey, direct interfacing, email and phone interviews reviewed the draft framework and provided feedback. The feedback were in two categories (1) impediments to implementation and (2) issues affecting the effectiveness of the framework. The study applied these concerns to improve the draft framework by enhancing visibility and developing implementation plan. The use of scientific community to validate framework aligns to established norms in the literature [37]. The combined strategies (survey and interview) likewise agrees to inductive and deductive methods, deemed adequate for studies with no prior theoretical framework [38]. The research strategies likewise agree to SPT, indicating that SB is value-laden, which practices are best developed through constructed conceptions of stakeholders in the environment. The study coupled the gap in dearth of prior theoretical framework in CRS in SB implementation using Theory of Innovation Diffusion. This thinking positioned SB as a form of innovation, which degree of diffusion is subject to observability, compatibility, trialability, complexity and relative advantage [39]. Roychowdhury et al [40] evaluated of the performance of Excel-based decision-support optimisation model for green building facilitation using related strategy and theory. The distribution of respondents in Figure 1 is adequate in terms of expertise, education and experience in sustainable building and sustainable construction researches.

Figure 1.

Profile of respondents in framework validation.

Mean score, Friedman and Kendell’s concordance tests were adopted to analyse the perception of stakeholders related to the performance of the developed model. The mean score determined the potentials of CRS in the framework to achieve significant CR and the overall performance of the implementation guidelines detailed in the framework using five criteria (observability, compatibility, trialability, complexity and relative advantage). The Friedman’s test explored variance in respondents’ perceptions about the effectiveness of the framework, while the Kendell’s concordance test appraised inter-rater agreement within sample of respondents on the overall effectiveness of the framework. The validity of mean score was benchmarked at scores (>3.00), while the significance of Friedman’s and Kendell’s tests conformed to the significance of p-values (values ±0.05). The statistical tests determined the hypotheses, which states that the perceived effectiveness of CIIFSUB does not vary, is inconsistent and insignificant.

The modelling of CIIFSUB adopted integrated definition for the final archetype. The tool allows stakeholders to view multiple processes on a less multifaceted perspective. It consists of functional steps that demonstrates actions prerequisite to achieve targeted goals in a framework [41]. Each step is a tailored process directed to pre-determined goals with opportunities for performance improvement and measurement [42].

Result and Discussions

Cost reduction strategies - secondary data perspective

The objective of CRS is to improve or eliminate cost drivers contributing to extra cost [2, 14]. Table 2 presents the matrix of CRS for the various project development stages based on literature synthesis.

Contextual cost reduction strategies – experts’ perspectives

Table 3 presents the summaries of the main categories emerging from the constructed perceptions of interviewees on the critical drivers and strategies for FCR. Respondents’ views were unanimous on the practices, which can improve cost performance toward diffused adoption of SB based on the postulated relationship between CRS and cost drivers. This consensus suggests that FCR strategies should tackle critical cost drivers that triggers extra cost. The main categories and themes emerging from the interviewing however differ from the position in the literature presented in Table 2. Although the variations were expected in line with the varying sustainable construction practices [43], the cause of variation is connected with varying certification schemes [2, 14]. Varying design standards are implemented across the developing countries. Different projects have earned the US Green Building Council awards [14]. Other design tools, stakeholders are familiar with include BREEAM, LEED and GreenStar SA. These tools are foreign to local sustainable construction practices in the study environment, while the development of in-country tool is ongoing.

Table 4 shows the perceived CR potentials of 25 strategies based on the results of round-two Delphi survey. Overall, all strategies are perceived significant CR parameters, the CR potential of 19 (76%) strategies is high with means scores ranging between 3.00 - 3.97. Six (24%) strategies also have very high potential to direct CR in SB project implementation, the mean scores for this band of strategies lie between 4.15 – 4.76. The strategies in this category include scheme design optioneering, value engineering, target and activity-based costing, use of locally sourced sustainable materials and certifying buildings using foreign assessment tools. Expert perceptions about the significance of the strategies also show consistency across the sample with insignificant variations. The standard deviations of their perceptions are less than 0.60 and 0.56 on the average to confirm they are important cost control mechanisms. The uses of foreign design guide in the research environment would offer the most effective strategy to achieving cost reduction.

Development of cost improvement and innovation framework for sustainable buildings

CIIFSUB outlined steps operative to assist stakeholders to navigate the implementation of SB with cost efficiency. The framework achieved CR goal by directing stakeholders’ attention to cost drivers within SB project systems and recommends innovative processes/resources prerequisite to achieve them. The framework recognised cost improvement as seeking small, but certain, modifications to current procedures, while cost innovation aims at key modification undertaken either to provide elaborate advancement of current approaches or to cause exclusively different procedure for achieving organisational goals [41]. Cost improvement/innovation is therefore, fundamental to the improvement of construction processes [51]. CIIFSUB integrates process innovation with proven cost improvement strategies to model actions prerequisite to CR in SB development. The philosophy underpinning the framework therefore embeds cost improvement and innovation as inclusive drivers obligatory to direct changes in methods different from extant approaches challenged by FC barriers.

Components of the framework

CIIFSUB has six components, namely: cost drivers, project phases, CRS, performance measurement, performance objective and feedback mechanisms (Figure 2). The feedback loop proposes to order dynamism and unceasing upgrading towards continuous functionality. The objective aims to achieve flexible and adaptable model that answers to the dynamics of continuous improvement using feedback from field implementation. This thinking develops from the premise that cost innovation is similar to technology, modified through adoption. The continuous improvement loop therefore distinguished short and medium-term CR targets in CIIFSUB from the life cycle orientation driving current advocacies for SB, additional to its flexibility anchored on performance improvement. The following section summarises each component.

Figure 2.

Cost improvement and innovation framework for sustainable building (CIIFSUB).

Document and mitigate cost drivers: Cost drivers refer to constraints affecting the cost performance of SB projects. The interview reported in Table 3 highlighted several cost drivers.

Target improvement on specific project development process/stage: CIIFSUB covered four stages in project lifecycle, namely: preparation/planning, design, procurement and construction. The four stages retain the optimal opportunities to decrease cost [30]. Sustainability concerns overlap diverse phases as evidenced in the varying stages of sustainability assessment [12]. The transactional costs that could prompt improvement occur during these stages [27]. Sustainability concerns are also best manage during early stages [4] and vast proportion of factors affecting the cost of SB manifest during the construction stage. In addition to the four project development phases, pre-project loop has emerged from the expert review and this stage seeks to tackle fundamental issues prerequisite to preparing the stakeholders for a comprehensive uptake.

Cost reduction strategies: CRS are actions that when implemented, can improve and innovate construction processes to optimise cost drivers towards CR. These improved practices are embedded cost/project management parameters for improving construction processes, with proven empirical CR history in practice and literature. Based on interview and literature data, CIIFSUB has 25 main CR strategies grouped into four project development stages (Table 3, 4 and Figure 2).

Assess performance expectancy: Performance measurement would facilitate evaluation of CRS for value for money during project and post-projects. Performance expectancy in the model highlights economic sustainability, select the criteria for assessment, decide techniques for assessment and seeks to apply measured data for performance improvement [37]. Process and output performance that is, the product (building) and product development processes are areas earmarked for measurement in the framework [52]. The study targets economic sustainability dimension because, only financial criteria are measurable within the scope of available data in most emerging markets.

Determine performance objective: The framework targets short-term CR, contrary to the predominant long-term cost-savings disseminated across literature [6]. Applied CR would therefore achieve decrease in FC within short and long-term to diffuse the adoption of SB. The performance objective of the study bring into congruence the goal of economic proficiency in the construction and use of SB. Economic proficiency describe the level where technical efficiency and diffusion of efficiency achieved equilibrium [53]. It refers to the point during implementation, where SB development diffuse uniformly based on clients’ request.

Target constant improvement based performance output: Unceasing advancement dynamics seeks to adapt the framework to varying development requirements, development settings and divergent practices. Constant cost innovation during the project phase using CIIFSUB therefore agrees to generic philosophy tailored to understand the effect of practice on costs, assess limitation of practice, improve and advance CRS, evaluate project output, monitor outputs and document feedback. Post-adoption assessment, feedback and supervision in innovation implementation is imperative to accelerate the adoption [54]. Literature is likewise replete with reports on post-construction failures in SB development [55, 56]; therefore, constant improvement loop would safeguard stakeholders against static performance evaluation outcome prevalent in conventional project settings.

Validity of the framework

The result of the validation survey showed that the prospect of CIIFSUB to reduce first cost of SB is high across the criteria assessed (Table 5; average MIS > 3.5). CIIFSUB obtained top rating in compatibility, followed by relative advantage (MIS > 4.00). The CRS in CIIFSUB and their overall level of effectiveness to achieved congruence with conventional CRS in the study environment was high. The visibility of cost improvement strategies, motivation to drive adoption and level of simplicity obtained moderate scores (MIS, 3.00-3.20). The test of variance (Friedman test) showed that the perceptions of experts related to the effectiveness of CIIFSUB varies (p (88.711, 0.00 < 0.05). The result directed the dismissal of the null hypothesis and affirmed that the high prospect of CIIFSUB to achieve significant CR varies among experts. The results in Table 6 further indicate high inter-rater agreement among experts (W, 0.672, p (0.000 < 0.05). The study further rejected the null hypothesis and accepted that the inter-rater agreement is significant. Varying perceptions about the performance of CIIFSUB is likewise consistent since the scope of SB vary across regions, suggesting that varying CR inputs are imperative in different project contexts.

The framework defined two stages to achieving CR using CIIFSUB (1) pre-project (short-term) and (2) project level (medium term) implementation plans respectively. The pre-projects actions would prepare stakeholders for the project phase by equipping requisite skills, awareness and designing relevant enabling policies. Pre-project actions would therefore tackle exogenous constraints to SB uptake. Specifically, these actions would resolve skills dearth through training, education and knowledge development, dissemination of benefits, advancement of the right mindset and developing the relevant incentives. Inclusive stakeholders’ engagement is imperative to drive effective implementation policies in both phases. The first phase requires comprehensive participation of the public authority through the guidance of professional bodies and their regulatory agencies. Public sector must drive policies focused on developing necessary incentives and development of standards, while professional/regulatory bodies must undertake training focusing on Continuous Professional Development and short courses.

The structured learning should focus on project design, management and assessment, tailored to specific tools, even though, training using in-country standard would incentivise the costs of training. Targeted learning must likewise understand the pedagogical issues affecting skills learning and knowledge development in each settings, since varying methods suit differing contexts [57]. Hybrid training pedagogies combined with andragogy and experiential learning models could invariably advance training and learning development for embedding sustainability knowledge and transfer of skills [58]. Therefore, pre-project actions should optimise the peculiarities of site-based training tailored to experience and hands-on-the-project for optimal results. Public authorities in emerging markets must also facilitate SB association and research bodies to advance assessment tools.

Project-phase actions implementation should begin with the development of certified pilot SB projects across the states and local councils to serve as springboards for supporting diffusion campaign. Different pilot projects of varying characteristics are necessary to reflect differing levels of demand. Public-private sector synergy is prerequisite in achieving the goals of pilot projects, through financing and marketing. Government could also incentivised pilot projects by donating land and facilitating permits. The effectiveness of pilot programs to drive this goal abound, Xiahou et al. [59] verified pilot projects useful tool in supporting innovation diffusion in industrial building sectors. Pilot projects would therefore provide marketing mechanisms to disseminate economic viability, while also serving as a tool for life-long skills learning and knowledge development.

CIIFSUB framework further introduces the necessity for constant evaluation of the performance of the discrete CR inputs during projects and post-projects. Performance feedback is an imperative task for stimulating the uptake and advancement of innovation. Sustainability performance assessment is however not an easy task [60], due to varying tools, which drive variability in the conceptions of sustainability. Developing in-country’s tools for sustainability assessment would ease performance measurement problems [43, 61]. The inclusion of financial criteria as indicators of cost-effectiveness in the framework targeted ease of measurement [52]. Dwaikat and Kherun [54] supported the importance of unceasing assessment of building’s sustainability performance based on cost effectiveness.

From the foregoing, CIIFSUB constitutes an economic sustainability process-based cost management model for bridging affordability gap in SB project implementation. Dearth of economic sustainability framework is seminal and cost-modelling perspective overarches [54]. The dearth of economic sustainability framework implies SB implementation is missing the benefits of technical efficiency. This feature again set apart, CIIFSUB from the prevalent environmental sustainability frameworks [62, 63]. Although, cost reduction remains the mainstay of CIIFSUB, its integrative processes operationally enlists social sustainability through inclusive stakeholders’ involvement (public sector, developers, professionals among others) to implement buildings with lower carbon footprint (environmental sustainability), the framework is therefore an integrative protocol. Stakeholders’ integration objective within the framework is therefore consistent, public sector’s actions and regulations were authoritative for CR and growth in the adoption of SB practices [64, 65], while Azari and Kim [66] embraced integration in evolving integrated design framework for green buildings.

The crux of this integrative framework is synergy of efforts as a departure point for achieving positive financial outcome in SB project execution. Integration within CIIFSUB suggests tackling climate change related challenges in the building sector has cost implication with pay-off incentives within short-long term, when affordability is enforced using CRS [67]. The results have validated a strong theoretical standpoint by showing that synergy between stakeholders’ and right policies would combat climate change impacts cost-effectively. Developing from SPT, the results affirmed that repetitive interactions in SB development, using CIIFSUB as the practice model will improve value (FC) towards diffused adoption. Therefore, practice innovation and interactions between stakeholders are fundamental to FCR [21, 22]. The understanding means that CR is not a set of realities waiting to be unearthed, but practices that must be developed through real-life projects. The development of SB and economical sustainability are not therefore disconnected, rather, the interaction between stakeholders and SB development practices underpins the FC.

Conclusions

Due to apparent of dearth of structured guidelines for navigating SB implementation cost-effectively, this study developed Cost Innovation and Improvement Framework (CIIFSUB) to aid new and existing adopters of SB to direct their implementation processes in the most cost-effective way. The high cost of SB deters motivations to diffuse their adoption and more critically in developing countries, where related practices are still emerging. CIIFSUB is an all-inclusive but focally, an economic sustainability process-based cost management model for bridging affordability gap during SB implementation. The goal is to achieve equilibrium in technical efficiency between the planned adoption and supply of SB in short to long-term. The philosophy of affordability within the framework advocates inclusive stakeholders’ engagement to implement innovative practices that would synergies interactions between CRS and factors inhibiting cost efficiency in two implementation stages. Stage one-pre-project, mandates training, education, skill development, awareness, development of standards and incentives prerequisite to improve stakeholders’ readiness for project leadership. Stage two-project stage activities, assigns systematic tailored interventions to innovate project processes to achieve CR.

The performance and philosophies of aggregated CRS within CIIFSUB varies, but the consensus showed that it is appropriate to achieve critical CR. Driving SB implementation using CIIFSUB portrays that their first costs would reduce based on the postulated interactions between CRS and cost drivers. Adaptation of CIIFSUB in practical project environment must progress on five heuristics, namely: appreciate cost implications of SB, assess costs constraints, apply CRS, evaluate performance of CRS in projects and provide feedback to improve the process. The study have developed a structured comprehensive project lifecycle framework for achieving first cost reduction in SB development in a typical emerging market. The study championed 25 strategies spread across the project inception, planning, design, procurement and construction states for achieving cost-economy during sustainable building project development. The study provides criteria relating to each dimension for easy structuration to different project contexts during adoption. Stakeholders therefore have a duty to apply learning during project implementation towards continuous improvement.

Amidst the exposition of pertinent guidelines and strategies for cost-effective sustainable building development, a few exceptions may prejudice the findings embedding this framework. The study used mixed data; the primary data are based on stakeholders’ perceptions that are unconnected to actual project implementation except few participants. The performance of the developed framework is based on the perception of stakeholders, not actual project experience. In addition, the framework shows the architecture of first cost reduction agenda for stimulating SB diffusion in emerging markets only, the postulated relationship between CRS and cost drivers is apparent. The research establish the need to validate the effectiveness of these practices (guidelines) as well as the severity of cost drivers using an elaborate project-data to determine their effects on cost premium. This frontier would unravel the extent of achievable cost reduction based on postulated interaction between cost reduction strategies and cost drivers. This new interface would provide one of the most imperative marketing tool to disseminating the motivation to adopt SB practices across the globe.