To reduce peak energy consumption of the buildings and decrease risk of black outs in power systems we must strengthen our attention to the reasons of summer overheating of the buildings. There are some objective reasons of increase in capacities of cooling systems and annual use of energy for cooling of the buildings in EU countries and we are limited to influence them. But we should upgrade understanding of subjective causes of dramatic growth of energy demand for cooling. Architects and building society as whole are abele to influence mind of investors and customers to improve efficiency of newly designed and renovated buildings. This study report list the reasons of overheating, shows some examples of the site tests and numerical analyses of the buildings accomplished by group of doctorate students of Riga Technical University and Latvia University of Agriculture.