Although attempts for formulating sustainable approaches in heritage management have been ongoing since the 1980s, sustainability dimensions in the context of ‘reconstruction’ have remained an unexplored research area. By investigating the case of the ruined Khaz’al Diwan in Kuwait, an architectural heritage site in the United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage (WH) Tentative List, we explore and compare the roles of the ‘cultural continuity’ and ‘environmental protection’ pillars of sustainability in reconstruction planning. By employing rapid ethnographic surveying and case study methods, we first investigate the approach to ‘cultural continuity’ from the State’s stance and through local community perceptions. Albeit with nuances, the surveying revealed a preference for historicist reconstruction. However, the Khaz’al Diwan, like most of the heritage structures in the Gulf region, was originally constructed with coral stone, which is now protected under environmental laws. How feasible is the use of replacement materials in terms of sustainability perspectives that is also acceptable from heritage perspectives? Considering the high cooling loads required in this climatic region, we prioritized the energy performance of the construction materials of the external walls and the roof. Computer simulations based on scenarios testing same-type and replacement construction materials revealed how the latter could be considered as an alternative in a historicist reconstruction. The discussion revolves around the environmental and cultural parameters that are instrumental in reconstruction planning. This ultimately highlights how reconstruction policies must be shaped to redefine the role and scope of material authenticity to accommodate the local environmental and cultural realities in the wider Gulf region and Middle Eastern context.