## 1 Introduction  
Historic buildings are increasingly considered in literature dealing with energy efficiency actions and renewable energy systems [1; 2; 3; 4; 5; 6; 7; 8; 9]. Recent projects such as Energy Efficiency for EU Historic Districts' Sustainability, Climate for Culture, and Efficient Energy for EU Cultural Heritage are some examples addressing the impacts of changing climate conditions on historic buildings. The projects propose energy-efficient retrofit solutions while respecting buildings' heritage values. Historic England has developed one of the most comprehensive guidelines that intends to adopt a holistic approach to historic buildings and energy efficiency. The guidance seeks to address every factor that affects energy use in the buildings and tries to balance saving energy, sustaining heritage significance, and ensuring comfort (a whole-building approach) [9]. However, although the emphasis is placed on heritage values, there is an assumption on what these 'values' are and how they should be retained [10]. These programmes rely mostly on research to integrate technology into the built heritage but do not explore users' heritage values' in depth. Qualitative research on heritage and energy efficiency began to show the connection between energy efficiency and values. For instance, [PERSON] [11] offers perspectives that underline a social negotiation of the values by inhabitants of old buildings and heritage professionals and involves concepts of climate change and energy efficiency. [PERSON] conducted ethnographical research of specialists, planners, and homeowners interested in renovating and retrofitting buildings of attributed historical value. [PERSON] and [PERSON] [12] conducted a study in Greece that included residents' approaches to heritage conservation and energy efficiency in neoclassical buildings. Their research explored how residents' meanings and values regarding historic buildings drive or inhibit energy-efficiency interventions. Their study involved semi-structured interviews with residents that revealed a conflict between the urgency to improve thermal comfort during winter through installing a mechanical heating system (at the loss of the original characteristics of the building) and against interventions on the facade of the building. The study found that in most cases, the changes made by residents complied with current legislation and the architectural significance of the building as most buildings were listed. Overall, we lack in-depth, qualitative studies on energy efficiency and heritage conservation. In this regard, [PERSON] et al. 's [10] research have understood and integrated heritage values into decision-making to improve the energy performance of the heritage buildings' stock, which motivated this research. [PERSON] et al. [10] show that decision making in thermal comfort improvement, energy efficiency, and heritage conservation is a sociocultural and dynamic practice. In the connection or discontinuity of elements (materials, competencies, resources, values, senses, and time), the decision-making process changes based on external factors surrounding the building (context, listed status, age, climate, and ownership status) [10]. In Mexico, [PERSON] et al. [13] reported on the heritage values attributed to historic buildings and how they change, drive, or prevent energy efficiency changes over time. Their study consisted of in depth semi-structured interviews complemented by monitoring indoors environmental conditions that revealed what users prioritise between energy efficiency interventions and heritage values. Their research shows a tension in the limitations on buildings with listed statuses, which restrict changes in use and prevent energy-efficiency interventions and highlighted that a fundamental requirement for developing effective energy policies, standards, and guidelines is understanding the meaning of heritage attributed by the users. More international approaches that contribute to decarbonising the built environment are needed.