Green retrofit of existing non-domestic buildings as a multi criteria decision making process

With increased awareness of natural resources depletion, environmental pollution and social issues, the importance of sustainable development has been emphasised. Sustainable development is accepted as a guiding principle to reconcile economic development with limited natural resources and the dangers of environmental degradation. The building industry is a vital element of any economy and can have a significant impact on the environment. By virtue of the large size of existing buildings, green retrofit of existing buildings is an effective approach to improve building sustainability and energy performance. Unlike domestic building retrofit, bound in the research, non-domestic building retrofit lacks a sufficient research and requires a further investigation. Green retrofit of existing buildings is a complex decision making process. With the rise of sustainability agenda in the building sector, it is essential for decision makers to consider sustainability criteria, which address environmental, economic and social performance. Due to the intrinsic characteristic of existing buildings, technical challenges can emerge when integrating green technologies or measures. The qualitative and quantitative nature of these multiple criteria can increase the complexity of the decision making process. In addition, the decision making process may involve stakeholders from varying backgrounds. The conflicting perspectives can be the main barrier in the decision making of green retrofits. This thesis proposes a framework for green retrofit of existing non-domestic buildings as a multi-criteria decision making process. The framework includes multiple phases: Site and Building Survey, Technology Listing and Screening, and Technology Evaluation with Multi Criteria Decision Making (MCDM) methods. By checking hierarchical information in the Site and Building Survey, basic information can be collected and implications for green technology can be gathered. The Technology Listing and Screening is used to propose potential technologies and further identify the qualified technologies. On top of these phases, technology evaluation with MCDM methods is suggested to conduct in four steps: 1) Criteria development by proposing a multiple criteria tree; 2) Criteria weighting by suggesting the default weights; 3) Technology scoring by presenting a simplified technology scoring approach; 4) Results synthesis. To propose the default weights, a professional survey has been designed to collect the views of experts from different backgrounds in the UK and China. Default weights have been suggested for all the expert group, the architect group, the engineer group, and other expert groups in both countries. The framework has been applied to one UK university building for the retrofit. The main findings are: by using the proposed framework, the possibility of selecting green technologies can be increased; by using the MCDM methods for technology evaluation, the technology ranking can be identified. Scenario analysis and sensitivity analysis have been conducted for technology ranking by applying different sets of default weights. Results show that the changes of criteria weighting for Cost and Payback period can lead to technology ranking changes in all the UK expert scenario. The changes of criteria weighting for all the criteria can lead to a change in technology ranking in the UK architect scenario.