Sustainable buildings are low impact elements in the world heritage. There is a biunivocal relation between the building renewal and the energy efficiency; in other words, it is necessary the former for obtaining the latter, and vice versa. In this research, the word "knowledge" gains two meanings: the first is related to the analysis of local resources and building constraints; the second, then, is to know the materials with which the technical solutions are designed. In order to ensure valid data, the numerical simulation represents a further step which takes into consideration variable climatic loads and different conditions of use.