Comprehensive energy, economic and thermal comfort assessments for the passive energy retrofit of historical buildings - A case study of a late nineteenth-century Victorian house renovation in the UK

This paper aims to evaluate the energy-saving potential, affordability and thermal comfort performance of various passive building retrofit measures for a historical building (late nineteenth-century Victorian house) renovation. Three types of interior passive retrofit measures (i.e. internal wall insulation, glazing upgrade and airtightness improvement), classified as traditional and advanced measures, are further grouped into 63 retrofit combinations. In order to evaluate the performance of these defined retrofit combinations, five assessment indicators are proposed, including energy reduction rate, specific initial cost, discounted payback period, space volume reduction rate, and indoor thermal comfort. Under three internal space reduction scenarios with a space reduction rate of 5.2%, 2.6% and 1.3%, these combinations are evaluated and compared, and the most favourable combinations are determined to achieve multiple objectives (maximum energy saving, most cost-effective and most energy-efficient). The influence of the most favourable retrofit combinations on the internal thermal comfort level improvement is also dynamically evaluated using the EnergyPlus simulation tool. The final recommended passive retrofit combination consists of vacuum insulation windows, gypsum air infiltration reduction, and 2 cm thickness of Polyisocyanurate (PIR) panels, with 51.8% of primary energy reduction, a specific initial investment of £144.71/m2 and a discounted payback period of 18 years.