Nowadays in the world, energy usage effectiveness has always been an issue which blocks people’s development. How to effectively use the energy is becoming more and more important. Energy audit can appraise the energy usage condition of a building, and come up with improvement advices through systematic calculation and analysis the existing problems and reasons for energy wastes, in order to bring the object of effective usage of energy into reality.

HiG student hostel 23 is situated in Gävle, a coastal city in the east of Sweden. There are three floors in Hostel 23, the first and second floor have 18 single rooms, 4 double rooms and 2 communal kitchens and the third floor is storeroom. The aim of this thesis is to explore indoor climate and energy use for this student hostel and find out the reason of the low temperature inside the room, seeking some ways to improve the thermal comfort inside the building during winter conditions.

First, collect date from every part in energy balance by measurement and interview with administrator, then calculate and analyze the data. At last, the whole energy balance can be estimated. Through analyzing the whole energy balance, the suggestion is to change the window type and design a new ventilation system operating plan. Through the optimization, energy loss is reduced, and about 10% of the energy is preserved. Besides this, the building infiltration loss is too high through this energy audit; it states there still exists some problems. If these problems can be solved, it will be helpful to keep a good thermal comfort inside the building.