Deep energy retrofit of historic residential buildings with the integration of prefabricated transparent insulation facades (TIF)

The energy efficiency of a building façade is significant for the carbon emissions of the whole building and for the sizing of the building’s energy system. However, it is challenging to insulate the façade of historic buildings due to the preservation of aesthetic, historical and cultural values of both interior and exterior surfaces of the wall which are typical in Victorian masonry residential buildings. This paper proposes an innovative deep energy retrofit strategy for Victorian residential buildings by integrating prefabricated transparent insulation panels (TIPs) with solar-assisted heat pumps (SAHP) and PV roof panels. Four alternative TIPs were investigated with single, double, triple, vacuum and PV glazing materials, which were applied to external masonry wall insulation with a 20mm air cavity between the external wall and glazing materials. Air convection was only allowed by the thermal buoyancy in the cavity for internally cooling of the transparent insulation facades (TIF) structures and to avoid the overheating issues in summer. Additionally, roof PV electricity could supply the SAHP system with stored hot water to provide both space heating (SPH) and domestic hot water (DHW). EnergyPro simulation was used to evaluate the carbon emission and economic performance with different retrofit packages. Results indicated that the integration of transparent PV glazing insulation façade (PVG), PVG roof and vacuum glazing window replacement with SAHP system, integrated with a water storage tank and batteries had the lowest payback period of 15-16 years with an initial investment of £323/m2 - £538/m2 and a 75.7% - 91.1% carbon emission reduction. In comparison, for with the scenario without façade insulation, the payback period was extended to 24-27 years, although the initial investment varied between £121/m2 and £410/m2.