In this study we aimed at evaluating the benefit of managing a digital mock-up for renovation operations in an ancient building. Focusing on thermal efficiency, the renovation proposal dealt with the great windows. We compared three methodologies dedicated to the project planning and management We first address the issue of the renovation of old buildings and come up with a workflow that connects the digital building to its lifecycle; then we focus on an instance of onsite handling of such data, in an augmented reality context, by elaborating the notion of “BIM in situ” as described in the papers of [3] as well as in [4]. Results reveal that handling BIM onsite through a mobile device is challenging but they also show that it brings more efficiency.