The aim of our research was to analyze heat energy consumption in public buildings managed by Riga City Municipality in the year 2008. Our stated data contained information about 424 public buildings, including data of heat and electricity energy consumption depending in building use, and data of the windows quality in these buildings. Data was analyzed subdivided all public buildings in twelve groups. They are: schools, special status education schools, academy of music, day care centres, hospitals, libraries, cult buildings, recreation centres, local government buildings, museums, sport centres and shelters. The largest groups are: schools (more than 100 units analyzed) and day care centres (also more than 100 units analyzed). Our analysis focused on heat energy consumption in buildings: a) After partial renovation with energy - efficient double – pane windows made with/ wihtout gas insulation between glass and frames from polyvinylchloride /PVC/ with heat transmittance U≤1.8 (W/m² *K), b) Not renovated with simple double - pane glass windows made from wooden frame with U≥2.5 (W/m² *K). In addition, we compared heat energy consumption in building groups with window covering more than 20% and less than 20% from the building facades. We have analyzed the data for each group separately. Our analysis show, that only windows change in buildings with partial renovation does not give heat energy consumption economy, but in some cases made it even bigger.