A field survey was carried out in order to collect, elaborate and analyse data concerning the actual energy consumption for space heating of a sample of about 140 buildings (120 high schools) in the Province of Torino (Italy). The buildings were equipped with heat meters. For each building the primary energy consumption (i.e. the fuel consumption multiplied by its net heat value), the metered supplied thermal energy, the daily and seasonal operating periods and the climatic data of the site were monitored. The energy consumption data, both annual and monthly, were normalised and statistically analysed in order to compare different buildings and different heating seasons. The study aimed at evaluating a "specific energy performance indicator related to space heating" for each building. This indicator may be used to establish benchmark values in heat energy service contracts, to predict heat energy consumption or to verify the increasing/decreasing of the actual consumptions in future heating seasons with respect to the benchmark value. Moreover, this is very useful to find out those buildings not complying energy requirements and, as a consequence, requiring a deeper energy diagnosis. The study is part of a research project between Politecnico di Torino and Provincia di Torino, stimulated by the Directive 2002/91/EC on building energy performance, focused on evaluating the energy performance of existing buildings. (C) 2007 Elsevier B.V. All rights reserved.