Multi-criteria assessments for environmental sustainability of buildings

In the last couple of decades there has arisen a crowded toolbox of quantitative methods used to assess construction sustainability. The evolution of the assessment systems shows the interest in quantifying sustainability with a range of very specific indicators. The majority of the existing sustainability assessment methods for buildings evaluate performance of buildings for a selected set of domains, with a lot of commonality. This study focuses on the building sector and as the first step relevant domains were identified though comprehensive analysis of available assessment systems. Site, energy efficiency, water efficiency, material, indoor environmental quality and waste and pollution are the identified domain for the study. Secondly, aspects of (criteria for) the selected domains were identified and the relative importance of the domains and aspects was established by an expert survey. Thirdly the overall domain weights were compared with those assigned by other rating systems, originating from different countries to find the correlation which can demonstrate the influence of national contexts for relative weights in rating systems. The fourth step is to analyse the applicability of continuous functions to assess the sustainability in contrast to step functions to facilitate ‘assessment’ rather ‘rating’ of buildings. Fourth aspect of this research is to establish the dependencies and influences between indicator scores within domains. The matrix representation was used to handle these direct and indirect influences. Finally the research focused on optimisation techniques that can be used to handle tradeoffs between indicator scores and to arrive at acceptable indicator combinations with optimised environmental sustainable scores for a given building. It was found that in the building hierarchy the “system” level is the most important, having over fifty percent of overall weight. In the building lifecycle, the “operation” stage is the most important phase. There is also strong coupling between the operation stage and system level. Good correlation was found between national statistics and the weights, demonstrating that national contexts influence the relative weights in rating systems. The outcome of the dependency evaluation shows that there are considerable dependencies between indicator scores. It was found that the proposed optimisation technique is truly useful to arrive at planning strategies that yield high environmental sustainability scores for buildings while accounting for negative dependencies