Economic and environmental prioritisation of potential retrofitting interventions in electricity decarbonisation scenarios: application to a heritage building used as offices

Abstract

The large amount of energy and materials consumed by buildings, together with their associated potential environmental impacts imply a cost that must be optimized, both economically and environmentally. The retrofitting interventions considered in this paper were: envelope improvement, installation of active energy systems (heat pump with hydronic floor and/or photovoltaic panels) to be integrated into the building, and the use of the electricity generation mix according to future energy and climate plans proposed by Governments hoping to achieve more environmentally friendly power generation. The decision-making process included several possible energy mix scenarios for each possible intervention (i.e., present, BaU-Mix; near future, NF-Mix, and long term, LT-Mix), with several variables in each (economic cost and environmental impacts calculated in turn for each stage of the life cycle). A multi-criteria approach was applied together with the use of some of the indicators which are widely used in the analysis of economic investments but nowadays are also applied to environmental impact assessments. These quick and easy to calculate indicators could be a useful tool for selecting the best economic and environmental investment. The indicators used were the payback period (PBP), the net present value (NPV) and the return on investment (ROI). The environmental impacts were those from Environmental Product Declarations methodology and the Cumulative Energy Demand (CED). The best solution to improve the sustainability of the heritage building would be achieved by improving the envelope (walls and windows) and adopting decarbonisation policies focused on the increase of renewable sources in the electricity mix, while the installation of active systems in the building is unnecessary.