Developing Bio-Inspired Sustainability Assessment Tool: The Role of Energy Efficiency ^†

Abstract

The escalating demand for sustainable development in the built environment necessitates the integration of innovative, system-based assessment tools. This study investigates the role of energy efficiency (EE) within a nature-inspired sustainability assessment framework, drawing from biomimicry principles to evaluate green building practices in South Africa. Grounded in the ethos of nature’s efficiency, such as closed-loop energy systems, passive energy use, efficiency through form and function, and decentralised and localised energy generation, this study identifies and prioritises key EE criteria, including efficient energy management, renewable energy optimisation, passive heating, ventilation and air conditioning (HVAC) systems, and energy-saving technologies. Using the Analytic Hierarchy Process (AHP), this research engaged 38 highly experienced, practising, and registered construction professionals to perform pairwise comparisons of EE criteria. Results revealed that efficient energy management (29.8%) emerged as the most significant factor, followed closely by energy-saving equipment (26.4%), with strong expert consensus (consistency ratio = 0.03). The findings reflect a convergence of ecological wisdom and industry expertise, suggesting that nature’s design strategies offer a compelling roadmap for achieving sustainable energy performance in buildings. This study reinforces the applicability of biomimicry in shaping context-specific sustainability metrics and informs the development of adaptive, ecologically aligned certification frameworks. This study recommends the integration of these EE criteria into building rating systems, fostering interdisciplinary collaboration, and scaling nature-based frameworks to inform global sustainability practice. By bridging theory and application, this study advances a regenerative approach to construction that aligns with the UN Sustainable Development Goals and long-term environmental resilience.

1. Introduction

The construction sector is one of the most resource-intensive and environmentally impactful industries worldwide, accounting for a significant share of global energy consumption, greenhouse gas emissions, and material waste [1,2]. As concerns about climate change, ecological degradation, and resource scarcity intensify, the demand for sustainable construction solutions has never been more urgent. Several practices, such as circular economy and lean construction, have been explored to meet the global sustainability targets of the construction industry [3,4]. Among the various explored strategies, bio-inspired design (popularly known as biomimicry), drawing on nature’s time-tested principles, offers a novel and promising pathway for enhancing sustainability performance in the built environment. Through billions of years of evolution, nature has perfected energy efficiency (EE), material optimisation, adaptability, and resilience strategies. The natural ecosystem offers resilient structures and materials with optimised topologies and morphologies for achieving excellent properties with sustainable performance [5]. Integrating these biological principles into sustainability assessment tools (SATs) can drive transformative changes in designing, building, and operating human habitats.

Current sustainability assessment frameworks such as LEED, BREEAM, and Green Star provide valuable benchmarks for measuring environmental performance. However, many of these tools focus primarily on compliance and quantitative metrics, often failing to capture deeper systems thinking or the regenerative potential of built environments [6,7,8]. They rarely consider how natural systems maintain equilibrium through efficiency and feedback mechanisms, nor do they fully integrate biomimicry as a core design or evaluative principle. These gaps limit the potential of these tools to drive holistic, long-term sustainability outcomes. There is growing recognition that sustainability assessment must be reimagined through a bio-inspired lens to move beyond “less bad” solutions and toward regenerative design and a truly sustainable path.

EE is one of the most critical areas where bio-inspired thinking can be applied. In natural ecosystems, organisms have evolved to utilise energy efficiently through passive design, cyclical resource flows, and adaptive behaviours [9,10]. The Namib beetle, termite mounds, and photosynthetic leaves are a few examples of biological systems optimised for minimal energy input and maximum performance [11,12,13]. Translating these insights into the built environment can inform architectural strategies such as passive ventilation, thermal regulation, and daylight harvesting. Yet, conventional assessment tools seldom or do not incorporate these nature-based performance indicators. This oversight limits our ability to learn from ecosystems operating sustainably for millennia, a gap this research bridges.

This paper aims to develop a bio-inspired SAT that places EE at the centre of its framework. By integrating biomimetic principles into the assessment of energy use in buildings, this tool aims to bridge the gap between environmental performance metrics and nature-based intelligence. This research explores how lessons from biology and the natural ecosystem can inform key design and operational criteria for energy efficiency in the built environment, ranging from building orientation and envelope design to HVAC systems and user interaction. Furthermore, this study proposes a conceptual model that aligns energy performance indicators with ecological analogues, offering a new paradigm for evaluating and improving building sustainability. Ultimately, this paper contributes to the evolving discourse on regenerative design by proposing a transformative building sustainability assessment approach rooted in biomimicry. It supports a shift from traditional, reductionist models to more holistic, sustainable and system-oriented thinking reflecting natural systems’ complexity and elegance. By positioning EE as a key area for biomimetic application, the conceptualised bio-inspired SAT enhances environmental performance and integrates nature-based innovation in sustainable construction. This paper is part of a larger study that comprehensively considers nature principles or Biomimicry Life Principles (BLPs) to develop a truly sustainable and user-friendly SAT for the built environment.

2. Research Methodology

This research seeks to establish a holistic sustainability assessment framework for green building projects, drawing inspiration from principles observed in nature (known as Biomimicry Life Principles). The conceptualised framework focuses on the Energy Efficiency (EE) dimension by structuring, analysing, and prioritising key EE-related elements. These EE elements are crucial for evaluating the sustainability performance of buildings within the South African context, while maintaining potential applicability in broader international settings. The EE component of the conceptualised framework was explored through empirical data collection to address the research objective. A structured, self-administered questionnaire was distributed to a carefully selected group of professionals actively engaged in sustainable construction practices across South Africa. This cohort comprised qualified and experienced individuals, including architects, project managers, civil and mechanical engineers, quantity surveyors, urban planners, electrical engineers, and construction managers. The respondents are registered with relevant professional councils and have participated in green-certified building projects. Clear and concise instructions were provided to ensure easy understanding and response accuracy.

Participants employed the Saaty scale (ranging from 1 to 9) to perform pairwise comparisons of the assessment criteria, facilitating the weighting process. The assessment criteria compared by the expert decision makers are extracted and adapted through a careful distillation and review of green rating/assessment systems, sustainable development goals (SDGs) of the United Nations and majorly the BLPs (nature principles). Figure 1 presents the conceptual metrics/criteria that are inferred from the bio-inspired attributes of EE as a core part of the developed sustainability assessment tool for the built environment. This study projects the significance and influence of EE toward the conceptualisation of a sustainable, nature-inspired and comprehensive framework for building assessment in South Africa. Of the 50 sustainability experts purposively sampled and invited to participate in this study, 38 returned valid responses, yielding a 76% response rate. This study utilised descriptive statistics to analyse the data and applied the Analytic Hierarchy Process (AHP), a multi-criteria decision-making (MCDM) method developed by Thomas L. Saaty in the 1980s. AHP allows for the systematic comparison of qualitative and quantitative factors within a hierarchical structure [14]. The methodology followed Saaty’s six-step process: problem definition, hierarchy development, pairwise comparisons, weight estimation, consistency verification, and final evaluation [15]. Descriptive analysis was performed using Microsoft Excel, while the AHP components were processed using the Goepel Excel template and Super Decisions Version 3 software, facilitating the synthesis, validation, and interpretation of expert judgments. The AHP implementation followed the standard sequence of hierarchy construction, comparative evaluation, weight derivation, consistency assessment, and result generation.

3. Findings and Discussions

An analysis of the respondents’ demographic characteristics reveals that most expert decision makers (respondents) hold a Master’s degree, accounting for 65.8% of the sample. This is followed by those with a PhD or equivalent doctoral qualification (28.9%), while a smaller proportion (5.3%) possess a Bachelor’s or Honours degree. Regarding professional affiliation, architects comprise the largest group at 26.3%, followed by quantity surveyors at 18.4%. Construction managers and construction project managers each constitute 13.2% of the respondents. A diverse mix of other professionals, such as civil engineers, electrical engineers, mechanical engineers, project managers, and town/urban planners, each represents 5.3% of the sample. Only one respondent (2.6%) was identified as an industrial engineer. Regarding industry experience, more than half of the participants (57.9%) have been active in the construction sector for 11 to 15 years, indicating considerable practical knowledge. A further 21.1% have between 6 and 10 years or between 16 and 20 years of industry experience, respectively, demonstrating a balanced mix of mid- and senior-level expertise across the sample. When asked about their involvement in green-certified construction projects, 65.8% of respondents reported participating in three to four such projects. Another 31.6% had been involved in one to two projects, while a small proportion (2.6%) had contributed to between five and six certified projects. This distribution highlights a moderate but consistent engagement with sustainable construction practices among the expert participants. All the respondents who participated in the study are duly practising and active members of their respective professional bodies.

The code definition of the identified materials’ efficiency criteria is as follows: EE1 (efficient energy management), EE2 (renewable energy optimisation), EE3 (a passive heating, ventilation and air conditioning (HVAC) system), and EE4 (the use of energy-saving equipment). Thirty-eight (38) responses were received from the experts (decision makers), and their judgements were aggregated using the geometric mean method, which combines judgements in a comparison matrix. As shown in

Table 1. Aggregated pairwise comparison for energy efficiency criteria matrix.

Categories	EE1	EE2	EE3	EE4
EE1	1.00	1.10	1.53	1.25
EE2	0.91	1.00	1.27	0.82
EE3	0.65	0.79	1.00	0.75
EE4	0.80	1.22	1.33	1.00

, all resulting collective judgements for pairwise comparison, as calculated and mapped into a single decision matrix, are presented. The eigenvalue approach was employed to determine the subjective weight of each element in the matrix. The normalised principal right eigenvector of the calculated EE criteria matrix represents the relative weights of the elements, which sum up to 1.0. The symbol W denotes the normalised eigenvector derived using the mathematical expression shown in Equation (1). As explained by Al Barqouni [16], the procedure for determining the relative priority weights from matrix A involves solving the following eigenvalue equation:

A × W = λmax × W

(1)

The weights for the pairwise comparison matrix showing values for the consistency ratio (CR), λmax (the biggest eigenvalue of the criteria matrix), consistency index (CI) and the random index (RI) are presented in

Table 2. Aggregated pairwise comparison for energy efficiency criteria matrix showing priorities.

Categories	EE1	EE2	EE3	EE4	Priority (W)	Rank
EE1	1.00	1.10	1.53	1.25	0.29787	1
EE2	0.91	1.00	1.27	0.82	0.24351	3
EE3	0.65	0.79	1.00	0.75	0.19445	4
EE4	0.80	1.22	1.33	1.00	0.26416	2
λmax = 4.009; CR = 0.03; CI = 0.01; RI = 0.89

. Since the number of elements (n) is four (4), which ideally is the rounded value of λmax [17], the RI is fixed and will be 0.89 according to the random index table by Saaty and Vargas [18]. For the judgement matrix to be deemed consistent, acceptable and valid, the value of CR should be less than 0.10 or 10% [19,20].

The results of the combined judgements and eigenvector values (priority weightings) are presented in Table 2. The table shows that the efficient energy management criteria (EE1) have the highest priority weighting under the energy efficiency category in the conceptualised bio-inspired SAT for the South African construction industry at 0.298, followed by the use of energy-saving equipment criteria (EE4) with a priority weight of 0.264, renewable energy optimisation criteria (EE2) with a priority weight of 0.244, and passive HVAC system criteria (EE3) with the lowest priority weighting of 0.194. Since the consistency ratio of the matrix (CR = 0.01) is less than 0.10, this implies that the experts (decision makers) were consistent in answering the pairwise questionnaire. The judgement matrix is therefore deemed consistent and the results satisfactory.

The weights of energy efficiency criteria were rounded to the nearest integer number for simplicity and practical use [21]. From Figure 2, it can be inferred that the efficient energy management criteria (EE1) contribute the highest weighting of 29.8% to the goal (energy efficiency category), energy-saving equipment criteria (EE4) contribute 26.4%, and the renewable energy optimisation criteria (EE2) contribute 24.4%. In comparison, the lowest contribution of 19.4% was attributed to the passive HVAC system criteria (EE3). The relationship between EE and the conceptualised bio-inspired SAT was statistically significant with a consistency ratio of 0.03 or 0.3%. This research study generally hypothesised that the energy efficiency (EE) category influences an effective bio-inspired SAT.

A descriptive assessment of the latent variables (criteria) of the EE category revealed that the experts/decision makers perceive all the variables to significantly influence the sustainability performance of the conceptualised bio-inspired SAT in the South African construction industry. The very high relative importance weighting of the variables and EE category by the experts (respondents) suggests their significance. At the same time, a consistency ratio value below 0.1 or 10% indicates the validity of the result. According to Hafez et al. [22], EE is one among the several effective pathways through which to achieve building sustainability. Therefore, selecting suitable renewable energy sources, designing them for optimal energy performance, and other considerations are key to attaining EE in buildings [23]. Hence, EE has become a critical consideration and evaluation criterion in notable SATs worldwide and the conceptualised bio-inspired SAT for the South African built environment.

4. Conclusions and Recommendations

This study successfully integrated biomimicry principles into the development of a sustainability assessment framework, emphasising energy efficiency (EE) as a critical dimension for evaluating green buildings in South Africa. The conceptualised bio-inspired SAT can also be adapted for other purposes and in other developing countries. By employing the Analytic Hierarchy Process (AHP), this research identified and prioritised four key EE criteria: efficient energy management (29.8%), energy-saving equipment (26.4%), renewable energy optimisation (24.4%), and passive HVAC systems (19.4%). The high consensus among the respondents who are experts (CR = 0.03) underscores the validity of these findings, which align with nature’s strategies for energy optimisation, such as passive design and decentralised systems observed in biological analogues such as termite mounds and photosynthetic leaves.

This study bridges a critical gap in the conventional and widely known SATs (e.g., BREEAM and LEED) by incorporating bio-inspired metrics (BLPs) that promote regenerative design rather than mere compliance. However, limitations include the regional focus and reliance on expert judgement from South Africa, which may require validation through empirical performance data in future studies. To encourage the adoption and implementation of the conceptualised framework and nature-based solutions, it is recommended that bio-inspired EE criteria be integrated into other rating tools. Interdisciplinary collaboration among experts, such as biologists, engineers, and architects, should be encouraged and funded to scale nature-based solutions (NbS) globally. It is further recommended that the government and other relevant stakeholders provide necessary funding for future research and legislation that supports the overwhelming uptake of bio-inspired solutions and strategies. By aligning nature’s time-tested paradigms and principles with the built environment, a truly transformative pathway toward a regenerative and sustainable sector that advances the United Nations Sustainable Development Goals (SDGs) is possible.