Influence of procurement systems to the success of sustainable buildings

Procuring sustainable building projects is usually complex, highly dynamic, and consists of multiple interdependent subsystems. The relationships between dependent and independent variables of project performance are complex, nonlinear, and involve large numbers of important feedback processes. System dynamics modeling is best suited to handle complex dynamic systems involving nonlinear relationships and both ‘hard’ and 'soft’ data. It is adopted in this study as a suitable approach to analyze the influences of different procurement systems on sustainable building success. Based on a previously established causal loop diagram of the relationships between the critical success factors, sustainable building project success criteria, and procurement system variables, a whole system dynamics model framework is built. Validation tests provide confidence in the model from both structural and behavioral aspects. The method is then demonstrated by a comparison between the influence of five procurement systems of design-bid-build, construction management, design and build, partnering, and integrated project delivery on sustainable building success by system dynamics model simulations. The results show the influence of integrated project delivery is most significant, followed by partnering and design and build due to a high level of integration and collaboration of these procurement systems. Design-bid-build being the most popular procurement system, however, requires minimal training and management for adopted in sustainable building development. The simulations also reveal the shortcomings of each procurement system when applying to sustainable building projects. The method has a clear potential application in the development of an effective set of policies to improve sustainable building success.