A model proposal for assessing environmental performance of building construction process

The measurable results of the adverse environmental impacts which caused by the processes and activities of the buildings, cause changes in the environment and this reveals the environmental performance of the buildings. The adverse impacts of a building on the environment start to arise with the construction process that is the first phase of the building life cycle in which many activities are carried out using a variety of inputs. However, studies that address the environmental performance of buildings and the behaviour that the construction industry has developed to reduce the environmental impacts of buildings seem to focus on usage phase, substantially. When this problem is examined in the context of Turkish construction industry and the national literature, it is seen that the search for precautions against environmental impacts of the buildings focuses dominantly on the usage phase of the buildings in a similar manner, while the awareness of the environmental impacts of the construction process does not exist. The basic argument which supports this attitude is the short period of time of the construction process in the building life cycle compared to the usage phase. In addition, being consist of several sub-processes that are sequent and simultaneous, the characteristics of the construction process, such as the uniqueness of each construction process and local building patterns / traditions, the lack of systematic information that can be used in the environmental management of the construction process, the lack of addressing the construction process in the existing environmental performance assessment methods which also do not meet the local requirements make it difficult to assess the environmental performance of the building construction process and cause to be excluded from the scope of the environmental performance assessment of the buildings. However, the construction activities have been increasing and it is predicted that it will continue to increase due to the growing population and changing requirements, and this reveals that the role of the building construction process on the environmental performance of the buildings should not be ignored. This thesis is aimed to provide a solution to the proposed problems by taking into account the characteristics of the Turkish construction industry and local requirements. For this purpose, firstly, previous researches that focus on the environmental performance of the building construction process are examined to reveal the solutions set forth to these problems. In these researches, the data which is used for the assessment is obtained through existing literature and previous researches, local databases, databases of existing life cycles assessment tools, on-site observations and measurements, questionnaires, interviews and panels conducted with experts and documents belong to previous construction sites. The assessments are mostly performed by using existing environmental assessment methods, developed mathematical models or statistical analysis. However, due to the characteristics of the building construction process, it is infeasible to conduct required number of on-site observations and measurements to develop a comprehensive environmental performance assessment model. Moreover, the databases used by the existing assessment methods do not contain data coherent with the local conditions. Therefore, it is obvious that there is a need for an assessment model which provides the flexibility for assessing different building construction processes and which can be used with local data available in existing conditions. Based on the above-mentioned information, the basic aim of the thesis is designated as the development of a model proposal to be used during architectural detail design and construction planning phases in which decisions related to construction process are made. The proposed model can be used by the interested stakeholders to set forth estimations and facts about the environmental performance of the construction process. Thus, it can be possible to define the improvement / prevention areas related to the environmental performance of the process. The proposed model gets its basic from the assumption that there are direct and indirect relationships between the components of construction technology, which are the main inputs of the construction process, and the environmental impacts of the process, and a decision-support model that focuses on the assessment of the on-site construction process of building element systems, which have a number of design options, is developed. The thesis consists of six basic stages, which seek for answers to the presented problems and to the research questions, as (A1) Analysis of Building Construction Process and Construction Technologies, (A2) Analysis of Criteria Used for Assessing Environmental Performance of Construction Process, (A3) Definition of Methods to be used for the Assessment, (A4) Development of the Model for Assessing Environmental Performance of Building Construction Process and (A5) Application of the Model. (A1) Analysis of Building Construction Process and Construction Technologies stage consists of qualitative data collection through the existing literature to analyse the scope and stages of the building construction process, the construction technology concept and construction technology components. According to this, it is revealed that the construction process is composed of the preparation of the construction site, construction of the structural system, construction of the building element systems, construction of the service systems and landscaping of the building surroundings. Then, construction technology is defined as the information, methods (processes, actions, techniques) and tools (materials, equipment, labour) used at each stage of the building construction process, and each component are analysed based on the literature and the coding and classification systems related to building production. The outcomes of this stage have been used for developing a new construction technology classification system based on the requirements of the model. (A2) Analysis of Criteria Used for Assessing Environmental Performance of Construction Process stage covers examination of international standards, life cycle assessment methods and tools, green building rating and certification systems, national legislation and previous researches to define the criteria used for assessing the environmental performance of the construction process. The international standards have been used in particular for the definition of the environmental assessment terminology. Life cycle assessment methods and tools and, green building rating and certification systems are examined and direct and indirect criteria related with the construction process are revealed. National legislation has been reviewed within the framework of regulations related to Human Health and Waste Management issues, which are among basic criteria of the environmental assessment. Previous researches that focus on the environmental performance of the construction process has been analysed within the framework of the assessment criteria which are used in the context of different aims and scopes. The information regarding the environmental performance assessment and environmental management issues obtained in this stage have been used to define the environmental performance assessment criteria for the construction process. (A3) Definition of Methods to be used for the Assessment stage consists of the analysis of the methods, which can be used for developing the model, through existing literature using qualitative data collection method. The model, which is developed on the basis of the relations between construction technology components and environmental performance criteria, is considered as a Multi-Criteria Decision Making (MCDM) problem and methods which are consistent with the aim and the scope of the study are determined. According to this, Fuzzy Analytic Hierarchy Process (FAHP) method is selected to be used to define goals / priorities of the decision-makers related to the environmental performance of the construction process. TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) method is selected to rank the architectural detail design and construction technology alternatives by using quantitative data regarding the construction technology components, while Fuzzy TOPSIS (FTOPSIS) method is selected to rank the alternatives by using linguistic statements. Afterward, the basic features and mathematical backgrounds of these methods are elaborated in detail. Besides, the basic principles to be considered in the selection of decision-makers are also defined in this section. (A4) Development of the Model for Assessing Environmental Performance of Building Construction Process stage explains the development of the proposed model using the information obtained in the previous stages. Firstly, the Construction Technology classification, which represents the on-site construction process of the building element systems, has been developed, using the information obtained during stage (A1). Then, the Environmental Performance Assessment Criteria for the construction process are defined based on the information obtained in the stage (A2). The basic assumptions used in the development of the proposed model are explained by defining the relationships between Construction Technology Components and Environmental Performance Criteria. Finally, the general structure and application steps of the proposed model, which is named as BiYSÇeP (EpaBCP), is explained in detail. (A5) Application of the Model stage consists of four applications, which represent the possible uses of the EpaBCP. In this stage, the different uses of the model are exemplified and the obtained results of each application are interpreted. For the applications, two ongoing projects, one of them was in the architectural detail design phase, while one is in the construction planning phase, were selected and two architects among the stakeholders of the processes were selected as to be decision-makers of the assessment processes. The selected detail design alternatives were assessed by the decision makers by using linguistic statements and also by using the quantitative data on the construction technology components gathered from the identified sources. Finally, the alternatives were ranked according to the environmental performances of their on-site construction processes using the Integrated FAHP-FTOPSIS and Integrated FAHP-TOPSIS methods, and the results are interpreted in relation to the components of the construction technology. At the end of the research, answers to the research questions and the possibilities, strengths and difficulties encountered in using EpaBCP are discussed, and some conclusions are drawn for future studies on this field. Accordingly, the flexible nature of the EpaBCP which allows assessment of different building construction processes based on the environmental performance goals/priorities of different decision makers, the possibility it provides for assessment through linguistic statements, the possibility to use existing local resources to get the quantitative data on construction technology components, the possibility to make assumptions by using the obtained results for making improvements in construction technology components which affect the environmental performance of the construction process and the possibility to provide implications for taking measures related to the construction process are the main positive features of the EpaBCP. However, the necessity of obtaining quantitative data from several different sources and the increase in the duration of this process, the increase of the number of mathematical calculations of the integrated multi-criteria decision making methods in relation with the increase in the number of alternatives to be assessed and the conflicts in the obtained results due to inappropriate selection of the decision makers are the main difficulties encountered in using the EpaBCP. These difficulties also provide some inputs for the future works in this research field and for the innovations which should be performed by the construction industry. Preparation of detailed catalogues and guidelines for the construction technology components which are used in the construction process and making them obligatory to be included in project and construction documents, development of a computer based program that includes the basic components of the EpaBCP in order to shorten the duration for the mathematical calculations and the organization of some trainings and seminars to ensure that stakeholders of the construction industry reach an adequate level of awareness of the subject are the main themes that constitute the future perspective of the study.