## 5 Conclusions  
International guidelines and policies on energy efficiency of historic buildings suggest that values of aesthetics and authenticity often determine the correct type of energy-efficiency intervention. However, in practice, users' values are often neglected; consequently, interventions can lead to the potential loss of value appreciated by users. 'Value' is a critical element in the user's decision-making process when there is a negotiation involving their thermal comfort requirement, energy bills cost reduction, and heritage conservation. For instance, residents may initially prioritise the aesthetics of original windows over the need for thermal comfort because of the potential loss of value. In contrast, the cost and the need for energy-efficiency changes may change over time [32]. In many listed buildings and protected areas, there is a set of values that the introduction of energy-efficiency interventions should not compromise. This concern becomes even more challenging in social housing characterised as a heritage site, which was examined as part of this paper, and which showed that residents might have their own value systems that may or may not align with official 'value systems'(for instance included in international guidelines and conventions). Thus, it is important to capture the complete sets of values so that regulations on the energy efficiency of historic buildings can better be contextualised. Mexico City has been through many urban management plans without significant progress. While one area has been conserved and renovated, another has been prioritised for commercial uses, exacerbating depopulation in housing buildings and resulting in abandoned, deteriorated buildings. Heritage management challenges should be addressed in future studies where questions on sustainability should also be included. This research adds to the knowledge base on this subject by using an example where no studies have been reported in Latin America. Therefore, examining Mexico offers a new understanding of the subject matter. The sociotechnical approach evaluated and explored the parameters of values, energy efficiency, and users alongside building components (including environmental conditions). The analysis, combined with systems dynamics [10], unveiled the complex and, to some extent, dynamic interrelationships of the parameters contributing to users' decision-making processes. The residents adapt to the conditions of the building and prefer passive actions that produce thermal comfort and low-cost solutions for them. In the same way, the dynamic and complex relationships identified in the paper illustrate that heritage values, preservation, thermal comfort, and energy-efficiency interplay when residents make decisions involving energy and thermal comfort interventions. By preserving the unique materials, occupants sustain the sentimental value associated with personal and family memories. When they conduct maintenance and interventions for conservation, they maintain the building and its authenticity for the generations to come. With the active participation of the users, the risk that deterioration and abandonment cause to the heritage site on a larger scale would be prevented. Mexico City has shown challenges for Historic Centres where user values and sustainable goals must be included. We advocate for a participatory approach, such as this one, in guidelines to sustainable design in the environment of buildings with historic value. **Author Contributions:** Conceptualisation, fieldwork in residences of the Historic Centre of Mexico City, formal analysis, and writing--original draft preparation, K.S.M.C. ; fieldwork supervision, K.F. and H.A.M. ; writing--review and editing, K.S.M.C., K.F. and H.A.M. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by SENER-CONACyT, Mexico, and the EPSRC Centre for Doctoral Training in Science and Engineering in Arts, Heritage and Archaeology (EP/L016036/1).