The building was selected for a detailed study of heating consumption that is located in the city of Gävle and the top fifth energy consumption in this city in 2006. Classrooms, workshops, offices and a restaurant with kitchen compose the building of two floors.The aim of this thesis is to design the best approach to reduce consumption and achieve a high efficiency of energy utilization in these companies. The project is going to optimize the system.Series of measurements are taken to achieve the heat losses. The heat losses are calculated through the building in the first step. Afterwards, with the result of ventilation, heating and electrical usage an energy balance is made to calculate the efficiency of the installation through the building envelop.It is to study the indoor climate within a building, as well as energy consumption for the entire building. In addition, it is also used to measure the temperature of ventilation systems and check the schedule of air supply.Analyze the result of the value that is measured. Improve some part of this building that reduces the heating consumption.At last give some suggestion like construction a new roof reduce the heat loss and change some door that is not correct in the building.