Exploiting BIM in energy efficient domestic retrofit: evaluation of benefits and barriers

Energy efficient retrofitting of the existing building stock is important because of the need to reduce CO2 emissions and improve building energy performance. The significance of refurbishing existing UK housing to help the government achieve its climate change targets has been widely recognised. However, the current practices for UK retrofitting, with one of the oldest domestic stocks in Europe, are still confronted by technical and social challenges such as late adoption of BPS tools, difficulties in effectively measuring energy consumption and disruption to users. Therefore, it is essential to improve the existing practices of the domestic retrofit process. Building Information Modelling (BIM) offers, potentially, a comprehensive and integrated platform for improving the retrofit process. Although BIM has been applied in many large-scale projects, it has not been used extensively for small-scale retrofit schemes in the UK. This study sort to test two common misconceptions – (i) BIM is only for complex large-scale projects; (ii) BIM is only for new projects - by investigating the potential implementation of BIM in energy efficient domestic retrofit in practice in the UK. This thesis has explored how the efficiency of the retrofit process could be improved through BIM implementation. A critical review of the literature was followed by a series of semi-structured interviews with professionals. An experimental study demonstrated why the existing simulation methods, such as ‘detailed modelling', are not effective and why it is necessary to enhance the existing practices. One of the main barriers to improving the efficiency of existing practices is using Building Performance Simulation (BPS) tools too late in the retrofit process. Based on the experimental study, the results of detailed modelling, using DesignBuilder, were very accurate; however, such results are frequently used in an evaluative rather than proactive way in the existing practices. Running energy simulation is a lengthy process and putting architectural information into the BPS tools not only requires more time than is usually available at the early stage but, also, defining the thermal view by energy experts is subjective. Furthermore, evaluating the accuracy of ‘standards and procedures' approaches, Standard Assessment Procedure (SAP) and Passive House Planning Package (PHPP), illustrated that analysing energy performance based on the inaccurate or notional assumptions, regardless of the unique characteristics of the projects are often arbitrary, unreliable and inaccurate. Therefore, BIM simulation approaches were evaluated and tested through a real-world case study. The scope of this research is limited to energy performance modelling process; however, the basic methods and principles could be also applied to other types of performance analysis. The experimental project, evaluating two BIM simulation approaches, integrated and interoperable BIM, provided the opportunity to evaluate BIM’s usefulness in energy performance simulation and assess the accuracy and reliability of the outputs compared with the results of two-years of monitoring a house. Integrated BIM simulation approach, Graphisoft EcoDesigner Star, provided effortless interoperability and improved the effectiveness of the process. However, the integrated BIM approach requires intelligent guidance and depends on the vendors to integrate performance simulation tools into their BIM environment. The interoperable BIM, through gbXML, can facilitate the integration of BPS tools in the early design stage. By improving interoperability at the early design stage and adopting BIM, identified challenges could be addressed, such as, uncertainty about the quality of retrofit measure, lack of interoperability between BPS tools and BIM, and time-consuming iterative modelling. The main contribution of this research is in identifying the barriers and potentials of BIM in energy performance simulation to enhance the existing practices of the retrofit process through the experimental study. However, this research is a starting point, where an initial analysis of the problem and its solution has commenced.