A prototype of interactive data visualization is proposed for Building Management Systems (BMS). The aim is to enhance traditional data presentation format such as graphs and tables to support expert users in early open-ended exploration of building data. Based on data recorded over 3 years in a real office building in Switzerland, a case study is conducted involving 12 practicing expert users with engineering background. Both exploratory and qualitative in nature, this evaluation allows to : (1) show the ability of expert users to use advanced visualization tools to derive meaningful conclusions in limited time, (2) demonstrate the relevance of visual analytics results for the building physics field.