When retrofitting existing buildings, especially listed buildings of historical importance, a pragmatic approach must be adopted to strike a balance between building conservation and energy conservation. This proposal for a deep retrofit seeks to look at a best possible solution as a starting point and provides a detailed analysis of energy losses from the building. Enabling a set of elemental priorities for retrofit facilitates informed decision making but also a step by step approach should budget constraints dictate. This means that proposals are largely future proofed and each element is considered to the best possible standard.