In terms of energy efficiency and the quality of the indoor and outdoor environment, heritage buildings are facing sustainability challenges. This study assessed the feasibility of using renewable energy sources based on air-to-water heat pumps with regard to preserving the historic values of the buildings and their ability to coexist with current energy efficiency and decarbonization requirements, and to prevent their neglect and degradation. A new approach is the use of Building Information Modelling to accurately determine energy demand and select a heating system based on renewable energy sources in such an unusual case as a heritage building. The analysis covers a selection of feasible scenario of the modernization of the over 300 years old building. A particular focus of the study is to compare the use different heat pumps systems. One is a reversible gas absorption air-to-water heat pump and the other is an electricity-powered compressor air-to-water heat pump. The building is currently supplied with a fixed-temperature boiler up to 550 kW with an open combustion chamber fed with coal. It was proven that the proposed retrofit scenario reduces final energy demand by 72.9%, while improving thermal comfort, cutting annual emissions by 121.1 Mg CO2 and 1.0 Mg PM10.