The article explains the stages of a research project aimed at establishing an analytical methodology to analyse the energy performance of existing buildings through Energy Signature (ES), a monitoring method in which measured consumption is related to climatic variables. The energy consumption of buildings represents a large percentage of the total consumption of a country. The consumptions are often higher than those actually needed to ensure optimal conditions for the comfort of a zone, due to both typological defects (poor thermal insulation, thermal bridges, etc.), and wrong behaviour of users. ES has a two-fold purpose: on one hand it can be used as a pre-energy audit by a professional to highlight the glaring problems. On the other hand it can be a valuable tool for raising end users' awareness. The goal of the present study is to define a new accurate calculation method, called MESH, aimed at characterizing the ES from a scientific point of view. In the article, the ES is applied to the heating period: the method can also be used to analyse other types of energy consumption, such as cooling and electrical consumption: in this case it is important to define the appropriate climatic variable. (C) 2012 Elsevier B.V. All rights reserved.