**6. Conclusion**

The purpose of this paper was to assess the current performance of the existing retrofitting of heritage buildings through the viewpoint of energy efficiency. Findings from the study support motivation for conducting this study as it shows that in terms of energy performance, the majority of retrofitting projects of heritage buildings are currently underperforming. This study has shown that the quantity of energy used in the retrofitting of heritage buildings depends upon how intensity the building is utilised and how the building is operated. Thus, to effectively deal with energy use in retrofitting of heritage buildings, it is necessary to understand the purpose for which the building is to be used, the energy use implications for the new use, the building characteristics and its energy using systems. In addition, adequate knowledge is required of the options available to improve energy utilisation, the techniques for modifying buildings and systems, and the feasibility of replacing portions of them. Thus, it is recommended that lower energy use should be a key consideration in determining the effectiveness of any proposed interventions to the retrofitting of heritage buildings. Energy consumption of the resulting interventions and the possibility of energy generation should be the means for evaluation of actions taken to rehabilitate heritage buildings. The wider benefits of improved energy performance in retrofitting projects apart from improved thermal comfort can become a strong contributor to sustainable retrofitting of heritage buildings. Although the challenging factors impacting sustainable retrofitting of heritage buildings are varied and total elimination of the factors is difficult. However, sustainable management strategies towards the minimisation of their energy use should be aimed at provided such ameliorating strategies would not contravene the conservation policies and the requirements for their protection. New technological approaches with measures for low energy use should be explored not just for their retrofitting and adaptation capability but also for their sustainability.
