Introduction Most industrialized countries, in particular the European Union countries, are in shifting phase from a fossilbased development to a sustainable development. Approximately 40% of the energy consumption in the European Union is attributed to buildings across the private and public sectors. The European Parliament Directive 2010/31 (The Directive 2010/31/EU) states that new buildings should consume very low amount of fossil-based energy (Nearly Zero Energy Buildings) by 2020. The Directive declares that all new buildings built after 31 December 2018 will have to be buildings with high energy performance and their required amount of energy should be mostly covered by renewable energy sources. Hence, energy efficiency has become a common target for all buildings, in particular historical buildings (Fotopoulou et al. 2018). Since buildings with historic value are less energy-efficient than modern ones, energy demand and indoor comfort expectations are critical challenges for them.