For decades, heritage buildings have been an example of resilience, but also low emissions and the core of our cities, towns and villages. A building that has no use or purpose is abandoned and lost. It is imperative to ensure their conservation and maintenance by making them accessible, affordable and easy to maintain but also habitable and that is only possible considering comfort as the main target. Heritage buildings represent an important part of our cultural identity. It is time to include them in the adaptation to a new social and energy model. This project aims to demonstrate that it is possible to improve the overall performance of heritage buildings while preserving their architectural and cultural identity. Given that the spectrum of heritage buildings is very broad and those protection laws may allow for different levels of intervention; the project aims to develop a set of solutions that can be replicated in different parts of Europe. The idea seeks to solve the problem of lack of comfort experienced in many heritage buildings where in many cases either there is no heating/cooling system or the use of the existing one entails a significant economic expense due to the need to air-condition large volumes of air. Achieving acceptable levels of comfort is something that will not only benefit the health of the users but will also help to make these buildings attractive places to develop different uses and thus help to preserve them. When we are faced with the energy rehabilitation of a heritage building in which we normally have construction elements with high thermal inertia, the most recommendable solutions to take advantage of this characteristic are usually to insulate the exterior with hygroscopic materials. Unfortunately, in many cases, this intervention is not possible due to problems with the alignment of the street or because the façade is protected. When the only solution is to insulate on the inside, other problems arise, such as humidity buildup.