The composition of the atmosphere deteriorates due to the constant increase of the CO₂  and other gases emissions. The dependence on energy sources, the surcharge of the electric system and the creation of urban heat island are some of the problems that we are called to deal with. The ,not too old, perception that all the energy problems of a building are solved by using even more mechanical equipment has no longer value. The decrease of the natural resources and the need of changing our attitude towards the environment impose the appliance of energy design on new or existing buildings.The current study involves with the energy upgrading of the building of the department of Architecture of the University of Thessaly. The study is divided in three parts, attempting through research the presentation of a proposal for the reduction of the energy consumption of the building.

The first part deals with the basic factors that affect the building’s energy behaviour, the  features of the environment and the specifications of the inside space so as the users feel comfortable.

At the second part the record of the building reserve of the tertiary sector and the procedure of the energy inspection are presented.

At the third part the measurements of the existing building are presented, the compare with the specifications that are valid and at the end the proposal for intervention in the light system and in the building’s shell.