The requirements onto today’s buildings have been constantly increasing in recent years, due to tightening regulations intended to reducebuilding’s carbon footprint, increasing expectancies toward indoor occupants’ comfort, and the availability of new, sustainable HVAC-systems only buildings had to improve their performance, also the AEC stakeholders involved in the planning process had to improvemethods, instruments and predictive calculations and simulations. The rising risk of failure got an immanent one, and the domain changedfrom single person’s responsibilities to design teams and iterative and comprehensive teamwork. This contribution highlights the building-physics related challenges that we were confronted with as building physics consultants for a set of newly constructed buildings of a famousand award-winning Austrian Architecture office. Different means of building performance simulation had to be deployed to answer complexplanning questions. Thereby, some of the tools had to be used in coupled form, while others had to be utilized for questions originally notwithin their scope. To end up on secure pages without altering the architectural appearance of the designs to much, both in-depthknowledge and command of the building physics related instruments as well as understanding about the motives and design agendas of thebuilding designers are required.