Development of performance criteria for sustainability evaluation of modular versus conventional construction methods

Abstract Modular construction has been recognized as one of the primary methods for sustainable off-site construction in the recent past. However, in a given building project, the process of selecting a suitable construction method among different options is still made based on anecdotal evidence. Thus, it is imperative to evaluate the life cycle sustainability of different construction methods. The sustainability evaluation criteria (SEC) comprise the triple bottom line (TBL) sustainability categories, i.e., environmental, economic, and social, in which each category includes numerous sustainability performance indicators (SPI) associated with different life cycle phases of a building. The most significant step for comparative assessment of the life cycle sustainability of buildings is to develop suitable SPIs. In this paper, a methodology is used to identify and select the appropriate SPIs for life cycle sustainability evaluation of modular and conventional construction. Through a comprehensive literature review, 33 TBL SPIs were identified to address the life cycle sustainability performance of buildings. In order to investigate the applicability (importance) of the identified sustainability indicators when comparing the sustainability of modular and conventional buildings, a survey was designed and conducted. Subsequently, the construction professionals' perceptions of the applicability of these sustainability indicators were captured on a 5-point Likert scale. The reliability of questionnaire was analyzed using Cronbach's alpha measure. Then, all the SPIs were ranked based on their severity index (SI) values ranging between 20 and 100% correspond to a severity scale from “very low” to “extremely high” importance levels. All the SPIs were ranked under the overall TBL SPIs as well as within their associated sustainability categories. The analyses showed that 33% of the environmental SPIs, 67% of the economic SPIs, and 42% of the social SPIs were rated equal to or greater than “high” on severity scale (i.e., Severity Index ≥75%). The economic dimension of sustainability is still the governing concern of the construction industry practitioners. Moreover, the results revealed that attention to the social dimension of sustainability is increasing compared to the environmental dimension. This paper contributes to the current body of knowledge by highlighting the most applicable indicators for comparing and contrasting the sustainability of modular and conventional construction.