Energy efficiency of cultural heritage is not only an engineer issue. Many professionals and Institutions have to be involved in the design process. Furthermore, the building survey plays a crucial role in providing opportunities to the designers to find the most compatible solution. This paper shows the "Galleria Borghese" case study, in Rome, which is one of the most important Italian museum. Recent literature defined the energy efficiency of listed buildings dedicated to museum as the most challenging environment. For this reason, this study explored the available rooms to guarantee Indoor Environmental Quality, architecture preservation and sustainability. The disruption caused by some plant breakdowns climate that have occurred in recent years provided stress to the visitors comfort and overall exhibited works unsuitable for their preservation. From an analysis of the current situation and the calculation of winter and summer thermal loads of the building and the ventilation air flow rates, the study shows some viable proposals having as objective: the reduction of the heat load of the building in summer, a better air exchange and overall a modernization of the plant expansion. A participatory process allowed to involve in the design architectural elements by converting them to a new role such as the chimney of fireplaces as part of the new HVAC system. (C) 2016 Elsevier B.V. All rights reserved.