Tången 2 is a building situated in Stockholm, Sweden. It´s built in the 1930s and contains both residences and businesses. The property owner, Diligentia AB, wants to lower the energy use in Tången 2. This report consists of an energy audit which clarifies the specific circumstances linked to Tången 2. Collected knowledge is then used, together with the results from the literature study, to decide energy measures to proceed with. Result from the energy audit suggests a high potential to lower the energy use. To calculate the potential energy saving of chosen measures, a model of the building was constructed in IDA ICE. Collected data from the energy audit was used as input in the model. Simulation results suggest that there are several possible measures to implement, both constructional and technical. Results from the economical calculations suggest that there´s a connection between energy saving and investment cost. Even though the energy saving potential of a single measure is significant, it´s not cost effective if it consists of a high investment cost. Results from the study are presented as a program of measures that will lower the energy use and save the owner money in the long run. This study shows that even for a building with big energy saving potential, it´s hard to lower the energy use significantly and maintain a profit. The program of measures suggested in this report has an energy saving potential of 11 % and an IRR of 7, 7 %.