Abstract

Sustainability has become an important initiative discussed and undertaken, not only by private buildings, but also by public buildings which both dealing with residential, office, commercial as well as hospital. Sustainable building is the practice of designing, constructing, operating, maintaining, and removing buildings in ways that conserve natural resources and reduce pollution. Rating systems provide effective framework for assessing building environmental performance and they measure a building’s sustainability by applying a set of criteria organized in different categories. A good Green Building Rating System (GBRS) should cover key indicators reflecting a building’s characteristics and keep their performance in balance. This paper proposed a knowledge-based expert system as a tool to assess the performance level of a green building based on assessment factors of green building rating systems. Analytic Hierarchy Process (AHP) and fuzzy logic is adopted in order to develop the knowledge-based expert system. The data for this research collected from the experts in the field via pair-wise and Likert-based questionnaires. Using AHP, the most important parameters of rating systems according to their weights selected to be incorporated in the Fuzzy Inferences System (FIS) of fuzzy logic model. The fuzzy rules (knowledge) discovered from the collected data for FIS to assess the performance level of the green buildings from the Environmental, Social and Economical perspectives denoted as SE2. The outcome of this research is accordingly a performance assessment tool that analyzes the effect of factors in developing the sustainable building.

Introduction

Sustainability initiatives are considerable in the erection of new buildings, in the operation and the renovation of existing buildings and nowadays it is apparent that it has important impact on the building industry. As one of key outputs of the construction indus- try, buildings largely reflect resources and waste impacts during its lifecycle. Construction activities in general known as resource intensive and the impacts reflected in consumption of natural resources and pollutions [34].

Generally, sustainability is the ability of a system to continue on an indefinite basis typically incorporating economic, social, and environmental issues. The concept emphasizes the integration of humans in nature and requires that human activity remain within bounds avoiding impact on ecological systems [36]. Achieving a low carbon economy through building usage is necessary as it is responsible for approximately 40% of CO₂ emissions  in  the UK and across the EU, therefore policies on tackling energy use through design and development is of priority [37].

The awareness and importance of maintaining sustainable developments within the planning and engineering sector has led many to look toward new and innovative ways to incorporate sus- tainability into their designs. The term ‘‘green’’ building defines environmentally friendly techniques and technologies used in the design and construction of the built environment [38]. The green building revolution is sweeping across not only the United States but also most of the world. This revolution is further fueled by the knowledge that the world has little time to respond to the growing dangers of climate change, especially  global  warming, and that buildings play a huge role in causing carbon dioxide emis- sions that drive global climate change [73]. Green building tech- nology for responsiveness to sustainable development is not only for private buildings but also for public buildings which dealing with residential, office, commercial as well as hospital has become a flagship of sustainable development in this century. Its goal takes the responsibility for balancing long-term economic, environmen- tal and social health [71,58].

Assessing the performance of green buildings is a critical task as the different rating systems emphasize different aspects of build- ing performance and has been an eye-catching topic these days [61,29,13]. Due to the fact that Men strive to increased comfort and financial independence, the effects of economic, and the qual- ity of life is being hampered. While at the same time are also neg- ative health effects that must bear from the damage due to the rising number of environmental catastrophes as result causes cli- matic change is experienced [48]. Sustainable building design will become a more common practice once interior environment pri- marily the productivity gains believed to be associated with the provision of high quality interior environments [24]. For example, research on environmentally friendly design and management sys- tems has being conduct over the life cycle of buildings [53,63]. Besides, there are various methods for assessing the performance of buildings. Many of these methods emphasize the impact of buildings on the global environment and individual health, focus- ing on energy use, indoor climate and other environmental issues [18].

MCDM or MCDA are well-known acronyms for multiple-criteria decision-making and multiple-criteria decision analysis. MCDM is concerned with structuring and solving decision and planning problems involving multiple criteria [40]. It has been utilized to solve many real-world problems [35,64,60,28]. Zadeh [74] intro- duced the concept of fuzzy sets to enable analysts to deal with imprecise and subjective concepts and to deal with linguistic vari- ables in various decision and evaluation applications. Fuzzy MCDM (FMCDM) problems [26,65,41,39,12,10], among which the ratings and the weights of criteria evaluated on imprecision, uncertainty, and vagueness are usually expressed by linguistic terms and then set into fuzzy numbers.

A research by Lu et al. [39] that integrated human actions and complex socio-economic themes into the process of New Product Development (NPD) in order to adapt its design to various competitive markets showed the effectiveness of Fuzzy Multi-Criteria Decision Making (FMCDM) in theme-based product evaluation. Their method combined MCDM with Group Decision Making (GDM) methods and proposed hierarchical operators to fuse the data obtained from both  human  evaluators  and machines.

We also take the advantage of MCDM and fuzzy set theory and develop an assessment tool for green buildings performance. In our proposed method, Analytic Hierarchy Process (AHP) is used for group decision making and ranking the performance assessment criteria and fuzzy inference system is applied for final performance evaluation of green buildings. Hence, in comparison with research efforts found in the literature, our work has the following differ- ences. In this research:

1. Using AHP, the performance assessment criteria for green build- ings are ranked and weighted from the SE2
2. Using fuzzy set theory, a new knowledge-based expert system for assessing the performance level of  green  buildings  from the Environmental, Social and Economical perspectives is pro- posed.

Benefits of green buildings

Implementation of green building practices is believed will pos- sibly achieve the three benefits, which is SE2 benefits [70]. The environmental benefits include: Biodiversity and ecosystems enhancement; Air and water quality improvement; Waste streams reduction; Natural resources conservation and restoration; and Minimizing the global warming.

While secondly, the economic benefits contribute to reduction in operating and maintenance costs; Green product and services creation, expansion and markets shape; Occupant productivity improvement; Occupant absenteeism minimization; Life-cycle economic performance optimization; Building image improve- ment; and reduce the civil infrastructure costs.

On the other hand, social benefits give to reduction in operating and maintenance costs; Green product and services creation, expansion and markets shape; Occupant productivity improve- ment; Occupant absenteeism minimization; Life-cycle economic performance optimization; Building image improvement; and reduce the civil infrastructure costs.

In a green building, energy efficiency used to describe in fulfill several criteria which need to be achieve. This include the use of energy efficient equipment, suitability of materials for the climate conditions, the service and amenities provided must fulfill the building use and the building should consumed less energy than the similar buildings. Besides, another  important  aspect  should be considered is the embodied energy in both building construc- tion and demolition [47]. Many countries have introduced to reduce the building energy in order to improve the energy effi- ciency in the building sector.

Since sustainable development with Social, Environmental, and Economical (SE2) principles encouraged to response to the mea- surement of carbon footprints, many rating systems were and being developed in order to assess the ‘‘green-ness’’ of green build- ings and many in the field are thinking about measuring the actual performance of them i.e. ‘‘ the performance of buildings that we considered green.’’ For instance, many countries have developed their own rating systems either by setting up their own parameters or by modifying from the rating tools developed in other countries. Green Building Rating Systems (GBRS) is one of such systems that measure a building’s sustainability by applying a set of criteria organized in different categories [11]. In these GBRS, the criteria perform various functions in measuring responsiveness  toward the sustainable development. GBRS can support the decision-making process and increase the efficiency of actions by simplifying, clarifying and making aggregated information available.

The problem and our contribution

Assessing the performance of green buildings in their post-occupancy stage is the most effective way to insure that a building obtained what degree of success in its design. As the green building approach should consider three main criteria are Social, Environmental, and Economical (SE2); hence, the assessment tool for measuring the performance necessarily to take these criteria into consideration [11].

Throughout the phases of building life span, environmentally friendly built environments should be associated with safety, secu- rity, wellbeing, convenience, reasonable cost and long-term adapt- ability. Satisfaction of these criteria achieves an optimal combination of SE2 values for buildings [14,15,32,66]. Social, eco- nomic, environmental and technological dimensions are all impor- tant in evaluating building performance [16]. A wide range of criteria have been developed in order to assess building performance; however, there is a lack of consensus on what factors constitute excellence in this area. Recently, several quantitative and qualitative approaches have emerged for assessing sustainabil- ity of buildings.

GBRS helps in evaluating the criteria performance in buildings that influences the society, e.g., energy consumption, waste pro- duction and indoor air quality, in order to improve efficiency. It is use as a tool to track performance and provide building owners and developers with a guide to assist in building more sustainably. Based on information from the Intergovernmental Panel on Climate Change (IPCC), if the approach to constructing and operat- ing buildings remains as the status quo, there will be major eco- nomic and environmental repercussions [6,11]. GBRS provide a way for continually updating practices and procedures to ensure continual improvement and innovation [6,11].

GBRS measure a building’s sustainability by applying a set of criteria, which organized in different categories and classified fac- tors to conduct the factor wise performance evaluation of build- ings. The existing models developed in the previous studies [46] for the rating systems adopt mostly quantitative methods, so there is a lack of qualitative evaluation regarding user’s interaction with green buildings. In general, research on green building rating sys- tems can be divided into two main areas: (1) identification of cri- teria for the development of rating systems, and (2) research area concerns on assessment and validation of green building rating systems. Such studies mostly emphasize energy performance in buildings and generally adopt quantitative methods. This is the reason why there is a lack of qualitative evaluation methods in term of exploring user experience of buildings.

In order for a GBRS to be widely recognized, it is critical that the system reflects and understanding to the needs of end-users [13,29,30]. By contrast, in this study, a fuzzy inference system employing fuzzy decision making rules applied to model the qual- itative aspects of human knowledge and reasoning process without employing precise quantitative analyses.

The questions that have been raised for this study are: (a) Which factors are important to assessing the performance of green building on the three main criteria of SE2 perspectives? (b) How AHP and fuzzy logic methods being employed for assessing the green buildings performance?

Hence, this paper discussed an efficient expert system devel- oped for performance assessment of a green building system with adopting Analytic Hierarchy Process (AHP) and fuzzy logic denoted as (fuzzy-AHP). Using these approaches, the system is constructed based on three main assessment dimensions in green buildings are Social, Environmental, and Economical denoted as SE2. These three main dimensions have been widely used in the most of the current rating systems. The main objectives of this research are twofold:

1. Evaluating and weighting the criteria for green buildings from the SE2
2. Developing a new knowledge-based expert system for assessing the performance level of green buildings from the SE2

In addition, the main contribution of the paper is an integrated fuzzy-AHP Logic approach for assessing the performance level of green buildings from the SE2 perspectives. Moreover, using fuzzy logic, the  fuzziness and nonlinearity of the impact of SE2  factors on performance are address properly. To the best knowledge of the authors, there are few empirical studies to assess the perfor- mance of green building using fuzzy sets theory and the majority of the previous researches are based on fuzzy multi-criteria based methods such as fuzzy AHP. However, for the first time this research work employed AHP and Fuzzy Inferences Systems (FIS), which is the process of formulating the mapping from a given input to an output using fuzzy logic, in a different and entirely new way for green building rating systems.

The remainder of this paper is organized as follows: In Section 2, the related work on green building rating systems is present. In Section 3, applied methodology for proposed expert system is explained fuzzy-AHP is introduced. Section 4 provides an empirical study. Finally, conclusions and future work is present in Section 5.

Conclusions and further study

In this research, an effort has been made to develop an expert system to assess the performance level of green buildings using AHP and fuzzy logic approaches. The assessment criteria have been selected from the literature based on the three main dimensions of assessment, Social, Economical and Environmental denoted as SE2 in this research work. The data for this research has been collected from the experts in the field via pair-wise and Likert-based ques- tionnaires. To select the most important factors in each dimension, we applied AHP prior to the fuzzy logic approach as fuzzy-AHP. Then, based on selected factors, an efficient performance assess- ment system based on fuzzy logic has been developed along with its FIS to assess the level of performance. All input variables in the FIS model used linguistic terms  modeled  as  Gaussian  MFs and for the outputs of model, we considered the Triangular MFs. With defining these MFs for all inputs and outputs of fuzzy system, 192 fuzzy rules were discovered to be used in the FIS. The results of proposed expert system showed the ability of fuzzy logic in evalu- ating the performance level of green building. In addition, the eval- uation results also demonstrated that the Environmental dimension is more important for performance level in relation to the Social and Economical dimensions based on the experts knowledge.

In  this  study,  some  implications  and  limitations  exist  which need to be focused and scrutinized in further studies. First, there were a small number of experts in fulfilling the survey for this study. As sophisticated analysis is derived by the large sample size of the respondents, there is a call for future study conducting a rig- orous study to examine the evaluation of Green Buildings from a large number of respondents; this also lead to generalize findings of the prospective study. Hence, from this limitation, we feel that collecting the data from the multiple sources can improve the scope of generalizability of the proposed fuzzy model. Second, in this research, the output of the FIS was restricted by  the design and number of MFs and rules of the knowledge-base in the Inference Engine. In this particular design, Triangular  and Gaussian MFs were used to represent the linguistic terms to assess the performance level. Thus, different MFs such as Trapezoidal or Sigmoid may yield different outputs and therefore they should be investigated, and we propose inclusion of this aspect in future research.